lsa & network types

GVHD: Nguyn Ngc i Bi Bo Co

SVTH: Phm Vn Dng _12201036_C12QM13 Page 1

MC LC

1 LSA .............................................................................................................................. 4

1.1 Gii Thiu V OSPF .................................................................................................. 4

1.2 Metric Ca OSPF ....................................................................................................... 4

1.3 Mi Trng Ca OSPF .............................................................................................. 4

1.4 Cc Gi Ca OSPF .................................................................................................... 4

1.5 Multi-Area ................................................................................................................. 4

1.6 Nguyn Tc Hot ng Cu OSPF ............................................................................ 5

1.7 S Lc V LSA ....................................................................................................... 6

1.8 Hot ng Ca LSA .................................................................................................. 6

1.9 Cc Loi Thng ip LSA ........................................................................................ 7

1.9.1 Type 1. Router LSA ................................................................................................ 7

1.9.2 Type 2. Network LSA ........................................................................................... 11

1.9.3 Type 3. Summary Network ................................................................................... 13

1.9.4 Type 4 & Type 5 ................................................................................................... 16

1.9.5 Type 6. Group Membership .................................................................................. 23

1.9.6 Type 7. NSSA ....................................................................................................... 25

1.10 Qu Trnh Chn DR V BDR ................................................................................ 29

1.11 Router ID ............................................................................................................... 30

1.12 Link State .............................................................................................................. 30

1.13 M Hnh ................................................................................................................ 31

1.14 Cc Type ca OSPF ............................................................................................... 31

1.14.1 R1 ....................................................................................................................... 31

1.14.2 R2 ....................................................................................................................... 32

1.14.3 R3 ....................................................................................................................... 32



1.15 Show Ip OSPF Neighbor ........................................................................................ 33

1.15.1 R1 ....................................................................................................................... 33

1.15.2 R2 ....................................................................................................................... 34

1.15.3 R3 ....................................................................................................................... 34

1.16 Show Ip OSPF Border-routers ............................................................................... 35

1.16.1 R1 ....................................................................................................................... 35

1.16.2 R2 ....................................................................................................................... 35

1.16.3 R3 ....................................................................................................................... 36

1.17 Show Ip OSPF 1 .................................................................................................... 36

1.17.1 R1 ....................................................................................................................... 36

1.17.2 R2 ....................................................................................................................... 37

1.17.3 R3 ....................................................................................................................... 37

1.18 Config .................................................................................................................... 38

1.18.1 R1 ....................................................................................................................... 38

1.18.2 R2 ....................................................................................................................... 41

1.18.3 R3 ....................................................................................................................... 44

1.18.4 R4 ....................................................................................................................... 47

2 NETWORK TYPES ................................................................................................. 50

2.1 Gii Thiu V Network Types Trong OSPF ............................................................ 50

2.2 Multicaccess ............................................................................................................ 50

2.3 Point-To-Point ......................................................................................................... 51

2.4 Broadcast ................................................................................................................. 52

2.5 Non-Broadcast ......................................................................................................... 52



2.6 OSPF Broadcast Network ........................................................................................ 53

2.7 Designated Router and Backup Designated Router .................................................. 55

2.8 Election Of DR/BDR ............................................................................................... 56

2.9 Point-To-Multipoint ................................................................................................. 57

2.10 Mi Trng Truyn Dn Nh Framerelay, ATM,X.25. ......................................... 58

2.11 Mo Hnh ................................................................................................................ 59

2.12 Config .................................................................................................................... 59

2.12.1 R1 ....................................................................................................................... 59

2.12.2 R2 ....................................................................................................................... 62

2.12.3 R3 ....................................................................................................................... 65

2.12.4 R4 ....................................................................................................................... 67

2.12.5 R5 ....................................................................................................................... 70



LSA & NETWORK TYPES

1 LSA

1.1 Gii Thiu V OSPF

OSPF (Open Shortest Path First) l mt giao thc nh tuyn dng link-state, s dng

thut ton Dijkstra Shortest Path First (SPF) xy dng bng nh tuyn.

OSPF mang nhng c im ca giao thc link-state. N c u im l hi t nhanh, h

tr c mng c kch thc ln v khng xy ra routing loop. L giao thc nh tuyn

dng classless nn h tr VLSM v mng khng lin tc (discontigous network)

Bn cnh OSPF cn s dng area gim yu cu v CPU, memory ca OSPF router

cng nh lu lng nh tuyn. OSPF cn c kh nng h tr chng thc dng plain-text

v dng MD5.

1.2 Metric Ca OSPF

OSPF s dng metric l cost. Cost ca ton tuyn c tnh theo cch cng dn cost dc

theo tuyn ng i ca packet. Cch tnh cost c IETF a ra trong RFC 2328.

Cost c tnh da trn bng thng sao cho tc kt ni ca ng link cng cao th

cost cng thp da trn cng thc 108/bandwidth vi gi tr bandwidth c cu hnh

trn mi interface v n v tnh l bps.

1.3 Mi Trng Ca OSPF

Multiple access (ethernet)

Point-to-point

NBMA (Non-Broadcast Multiple Access).

1.4 Cc Gi Ca OSPF

1.Hello.

2.Link State Database Description (LSDB).

3. Link State Request(LSR).

4. Link State Update (LSU).

5. Link State Acknownledgement (LSA).

1.5 Multi-Area

Link State Update c chia lm 7 kiu.

+ Kiu 1: router link entry.

+ Kiu 2: network link entry (c to ra bi DR).

Kiu 1, 2: ch c to v gi gia cc router trong mt area, trong bng nh tuyn l

ch O.

+ Kiu 3: ABR Router gi thng tin summary v link state ca area ny cho area khc

thng qua backbone area (area 0).



+ Kiu 4: ABR Router gi thng tin v ASBR (nu c) ca area ny cho area khc thng

qua backbone area (area 0) nhng lu Stubby Area v Totally Stubby Area khng nhn

kiu 4 ny.

* Thng tin v ASBR: Router ID ca ASBR Router ch khng phi v cc thng tin

network m ASBR Router bit.

Kiu 3, 4 summary link entry: c to ra bi ABR Router, trong bng nh tuyn l

ch O IA.

+ Kiu 5: autonomous system external link entry, c to ra bi ASBR Router:

* Miu t tuyn ng ca cc AS khc (mun n AS khc th phi i qua ASBR), gi

n ton b OSPF Router trong area c ASBR Router, sau c chuyn n cc area

khc thng qua ABR Router (Nh l cc ABR Router khi bit thng tin v ASBR Router

s gi kiu

* Lu Stubby Area v Totally Stubby Area khng nhn kiu 5.

* Trong bng nh tuyn l ch O E1 c gi tr cost c cu hnh hoc O E2

mc nh c gi tr cost bng 20.

Mt vn cn lu y l cc router thuc Stubby Area hay Totally Stubby Area

khng cn nhn thng tin kiu 4 v kiu 5, ch cn cu hnh ng default route -> gim

database cho router. Cc router thuc cc area khc phi nhn c c kiu 4 v kiu 5

mi c thng tin n c cc network thuc cc AS khc.

+ Kiu 6: multicast OSPF, Cisco khng h tr.

+ Kiu 7: autonomous system external link entry, c to bi ASBR Router, trong bng

nh tuyn l ch N1 hoc N2:

* Chnh l kiu 5 c bit khi ASBR thuc NSSA (Not So Stubby Area),

* Kiu 7 ch c trong NSSA, miu t tuyn ng kt ni n AS khc v khi chuyn

sang area khc th phi qua ABR v c ABR chuyn i thnh kiu 5.

1.6 Nguyn Tc Hot ng Cu OSPF

Trong OSPF c 5 loi gi tin: Hello, Database Description, Link State Request, Link

State Update v Link State Acknowledge.

- Hello: dng pht hin, trao i thng tin vi cc router k cn (neighbor)

- Database Description: dng chn la router no s c quyn trao i thng tin

trc

- Link State Request: dng ch nh loi LSA dng trong tin trnh trao i cc gi tin

DBD (Database Description)

- Link State Update: dng gi cc gi tin LSA n router k cn yu cu khi nhn

c thng ip Request

- Link State Acknowledge: dng bo hiu nhn c gi tin Update.



1.7 S Lc V LSA

LSA (Link-State Advertisements) l thng ip (message) m router qung b v trng

thi cc links

Khi mt thay i xy ra trong h thng mng, router cm nhn c s thay i s to ra

mt LSA thng bo v s thay i

Sau khi c to ra, LSA s c gi qua a ch multicast n cc neighbor router. Hai

a ch c s dng l 224.0.0.5 v 224.0.0.6

Mi router sau khi nhn c LSA s ngay lp tc forward n cc neighbor router ca

n nh vy s m bo vic ng b thng tin gia cc router.

1.8 Hot ng Ca LSA

Mi mt LSA c nh s theo th t (sequence number), ng thi mt b m s

c kch hot xc nh xem LSA n lc "time out" hay cha. Vic ny nhm loi

b bt cc thng tin ca cc LSAs c. Mc nh ca Cisco l 30 pht (i vi JUNIPER

mc nh l 50 pht)

Khi nhn c mt LSA, router s so snh vi LSDB hin ti ca n. Nu LSA ny cha

thng tin mi, n s thm vo DB, sau chy thut ton SPF cp nht thng tin mi.

Nu LSA c gi n t mt Router ID sn c trong DB, sequence number s c so

snh, LSA c hn s b loi b. Nu l mt LSA mi s c thm vo DB, SPF c

chy li. Nu nhn c mt LSA c hn, LSA mi hn s c gi ngc li cho router

gi LSA c.

Sequence number thay i khi:

-LSA thay i v mt route c thm vo hoc b xa i

-Thi gian sng ca LSA ht (m nh LSA updates c flood bn trong area sau

mi 30 pht).



1.9 Cc Loi Thng ip LSA

1.9.1 Type 1. Router LSA

M t trng thi, cost ca kt ni n router neighbor v IP prefix ca cc kt ni dng

point-to-point.

+Type 1 Router LSA c ngun gc t tt c cc b nh tuyn n cc router khc trong

cng khu vc v thng tin trng thi ca cc lin kt kt ni trc tip ca n (giao din)

cc b nh tuyn v cc mng khc. Loi 1 LSA b ngp nc trong khu vc c

ngun gc v khng bao gi i qua mt khu vc ranh gii. ID Link-State ca Type-1

Router LSA l Router ID ca router ngun gc. ID lin kt nh nc v cc lnh vc

Router qung co trong tiu LSA l tng t cho Router-LSA.



+ Cc trng trong OSPF Type-1 Router LSA:

+Cc lin kt ID, lin kt d liu, lin kt Loi, S TOS, Metric, TOS, v TOS lnh vc

mt xut hin mt hoc nhiu ln trong mt Router LSA tng ng vi s Lin kt

trng.

+Lu : Cisco ch h tr TOS = 0. ToS v ToS lnh vc Metric xut hin tng ng vi

s lnh vc TOS. V d: Nu s TOS l 2, s c 2 t 32-bit c 2 trng hp ca cc lnh

vc ny. Nu s TOS l 0, s khng c trng hp ca cc lnh vc ny. Di y lit k

cc ID lin kt v lin kt d liu gi tr cho cc khc nhau Type-1 Router LSA loi lin

kt:



+ [1] - Gi tr ny thng bt u bng 0. Khi i tng kt ni l router khc, cc lin

kt ID l ging nh ID Link-State trong tiu Router LSA ca cc b nh tuyn ln

cn. Cc lin kt ID c s dng tm ra Router LSA ca cc b nh tuyn ln cn

trong qu trnh tnh ton tuyn ng. Mt giao din qu cnh l mt pht sng hoc giao

din NBMA c t nht mt ngi hng xm OSPF. Mt mng li vn chuyn c m

t bng mt loi 2 mng-LSA. Mt giao din cn s khai c th l mt loopback, pht

sng, im-im, hoc giao din a im trn m khng c hng xm OSPF. Mt router

OSPF qung co mt giao din a truy cp nh mt lin kt cn s khai min l n

khng c hng xm ca OSPF c th truy cp thng qua giao din. Khi k vi OSPF

hng xm mi n nh nc y , cc b nh tuyn OSPF thay th lin kt cn s

khai nh mt lin kt vn chuyn v qung co ca n Router LSA vi mt s th t

tng ln. Mt router OSPF to ra mt n Type-1 Router LSA cho mi khu vc m n

thuc v. Lu : Mt gi OSPF Router-LSA l b phn mnh khi c hn 119 LSA mc

trong mt gi tin OSPF khng c thm nh duy nht trn mt lin kt Ethernet vi

1500 byte MTU.



Shows the interfaces trn RT1, RT2 v RT3:



Shows cc Type-1 Router-LSA t RT2:

1.9.2 Type 2. Network LSA

M t s lng router v subnet mask trn segment mng.

+ Loi OSPF LSA 2, cn c gi l LSA mng, c s dng m t tt c cc mng

qu cnh, c hai pht sng hoc khng pht sng. Mt mng li giao thng c nh

ngha l bt k lin kt m c hai hoc nhiu hn cc b nh tuyn gn lin vi n. Type

2 LSA l ngun gc bi cc Router (c DR) ca lin kt, v Type 2 LSA lit k tt c cc

b nh tuyn c gn lin vi n, bao gm c DR chnh n.



+ Type-2 Network-LSA c ngun gc t cc DR trn mt mng li pht sng hoc a

truy cp (v d: Ethernet) lit k tt c cc b nh tuyn m gn lin vi mng li

vn chuyn. LSA type 2 b ngp nc trong khu vc c ngun gc ch. ID Link-State ca

mt loi 2 mng-LSA l giao din a ch IP vt l ca DR kt ni vo mng v qung b

LSA.

+ Cc trng trong OSPF loi 2 Network-LSA:

+ Type 2 Network-LSA c ngun gc t GTNT2:



Lu : Type 2 Network-LSA l khng cn thit c to ra cho cc giao din mng

LAN. Type 2 LSA c to ra ch khi cn thit, trong c nhiu hn mt b nh tuyn

gn vo mng LAN.

1.9.3 Type 3. Summary Network

M t ch n ngoi area nhng cng OSPF domain. Thng tin tm tt ca mt area s

c gi n area khc.

+ Type-3 Network-Summary-LSA c ngun gc t mt ABR qung co cho cc mng

con trong mt khu vc (b qua cc thng tin ca Type-1 v loi 2 LSA) cc b nh

tuyn ln cn bn ngoi khu vc. Loi 1 v loi 2 LSA trong mt khu vc, khi mt

ABR nhn Type-1 hoc loi 2 LSA, n s to ra mt type-3 LSA cho hc mng thng

qua cc Loi-1 hoc loi 2 LSA khc khu vc.

+Cc type-3 network-summary-LSA v Type-4-ASBR Tm tt LSA c nh dng tng

t, vi s khc bit v ni dung ca cc lnh vc ID Link-State Loi LS v trong tiu

LSA. Cho Type-3 LSA, ID Link-State l a ch IP ca mng ang c qung co, trong

khi cho Type-4 LSA, ID Link-State l Router ID ca ASBR ang c qung co.



+ Trng trong OSPF Summary-LSA

+ Type-3 Network-Summary-LSA khng c tm tt v do khng cha cc tuyn

ng tm tt theo mc nh.

+Tt c cc mng con trong mt khu vc s c qung co theo mc nh. OSPF khng

thc hin autosummarization nh RIPv2 v EIGRP.

+ Tng kt tuyn ng trong OSPF yu cu cu hnh th cng. Tng kt tuyn ng v

lc ABRs lun lun cn c xem xt do bn cht l mt type-3 LSA s c qung b

vo khu vc xng sng cho tt c cc mng trong khu vc c ngun gc, c th gy ra

vn l lt ng k. Tng kt tuyn ng v lc trn ABRs cung cp kh nng m

rng ln hn cho OSPF.

+ Lu : Type-3 v Type 4 summary-LSA khng mang thng tin m hnh, h mang tin

t ch IP hoc mng con. Bn tm tt LSA l c ngun gc bi ABR vi cc quy tc sau

y:

T mt khu vc khng xng sng cho cc khu vc xng sng, Summary-LSA c

to ra cho cc tuyn ng kt niv cc tuyn ng ni b khu vc . Ch c cc

tuyn ng ni b khu vc c qung co vo khu vc xng sng trnh vic nh



tuyn vng. Nu c bt k tuyn ng lin khu vc n t mt khu vc khng xng

sng c ngha l xng sng l khng lin tc, v OSPF khng cho php xng sng k.

T khu vc xng sng trong mt khu vc khng xng sng, Summary-LSA c

to ra cho kt ni cc tuyn ng, cc tuyn ng ni b khu vc, v cc tuyn

ng lin khu vc .

+Trng Route qung co trong tiu LSA ca mt Summary-LSA cha cc Router ID

ca ABR m to ra cc summary-LSA.

+ Bng nh tuyn v type 3 Network -summary-LSA nhn c trn RT4:



+ OSPF router phi thc hin tnh ton SPF trn nhng thay i trong ni b khu vc cu

trc lin kt (Type-1 v Type 2 LSA), nh nhng thay i ny tc ng vic la chn con

ng tt nht i vi im n trong khu vc. Thay i trn Type-3 LSA khng kch

hot mt tnh ton SPF, nh cc thay i ny khng nh hng n cu trc lin kt gia

mt b nh tuyn OSPF v ABR.

1.9.4 Type 4 & Type 5

Summary ASBR : M t thng tin ca ASBR. Khng c summary LSA type 4 trong mt

single area.External LSA : M t cc tuyn ng i n cc ch ngoi OSPF domain.

Mi External LSA biu din cho mt subnet.



+Type-4 ASBR-Summary-LSA c ngun gc t mt ABR m nm trong cng khu vc

nh ASBR xc nh cc ASBR v m t cc tuyn ng n ASBR. Type-5 LSA b

ngp nc cho tt c cc khu vc nhng cc thng tin chi tit t c ASBR c th

khng c mt tt c cc khu vc. Vn ny c gii quyt bng cch c mt ABR

m t cc tuyn ng n ASBR c ngun gc Type-5 LSA. ID Link-State ca Type-4

LSA l Router ID ca ASBR.

+Type-5 AS-External-LSA c ngun gc t mt ASBR v cha thng tin nhp khu vo

mt OSPF min t cc qu trnh nh tuyn khc. Type-5 LSAs c flooded thng qua

tt c cc lnh vc ngoi tr khu vc cn s khai, khu vc hon ton m, v NSSAs. Khi

mt router cn s khai nhn Type-5 LSA t mt b nh tuyn trong khu vc cn s

khai, cc LSA s b t chi. ID Link-State ca Type-5 LSA l a ch IP ca mng bn

ngoi ang c qung co.

Lu : cc tuyn ng ni b lun c a thch hn cc tuyn ng bn ngoi.

Khng c Type-4 v Type 5 LSA khi khng c ASBR trong mt min nh tuyn

OSPF.

Tt c cc router OSPF trong mt lnh vc nh tuyn duy tr cng mt Type-5 LSA

trong . LSDBs ca h

Tt c cc loi LSA c phm vi ngp lt khu vc (khng b ngp lt qua bin gii khu

vc); mong i Type-5 LSA c AS l lt phm vi (trn ngp khp mi lnh vc).



+ Cc trng trong OSPF AS-External-LSA:

+Di y lit k cc tiu ch mt b nh tuyn OSPF ci t mt AS-External-

LSA vo bng nh tuyn ca n:



++Cc b nh tuyn phi c kh nng t c ASBR thng qua mt con ng ni

b khu vc, lin khu vc, c ngha l phi c mt Type 1 Router LSA hoc Type-4

ASBR-Summary-LSA to ra cho ASBR.

++Chuyn tip a ch phi c bit n thng qua mt khu vc trong ni b hoc lin

khu vc tuyn ng. Mt s liu ca 1 ht ging mc nh s c s dng phn

phi li cc tuyn ng BGP, trong khi mt s liu ca 20 ht ging mc nh s c

s dng cho cc tuyn ng phn phi li t cc giao thc nh tuyn khc, bao gm

cc tuyn ng tnh v giao din kt ni trc tip.

+Cc s liu ht l mt thc o cho cc tuyn ng bt u phn phi li. Di y

cho thy cc bng nh tuyn, cng nh Type-4 ASBR-Summary-LSA v Type-5 AS-

External-LSA nhn c trn RT4:



+Lu : . Type-4 LSA khng c dch trc tip t c s d liu trng thi kt ni vo

bng nh tuyn

Lu : Gi tr s liu trong mt Type-4 LSA cho thy chi ph t ABR t c

ASBR. Gi tr ny c s dng bi b nh tuyn trong mt khu vc xc nh ABR

gn nht mt con ng bn ngoi.

+Cc nh tuyn nh danh bng cho OSPF:

+S khc bit gia bn ngoi Type-1 (E1) v bn ngoi Type 2 tuyn ng bn ngoi

(E2) l cc s liu ca mt ng E1 cng tng t nh cc s liu OSPF trong cc s

liu bn ngoi ang c tch ly vi cc s liu ni b ca tt c cc lin kt trn con



ng chuyn tip hng ti ASBR, trong khi cc s liu ca mt tuyn ng E2 vn

gi nguyn nh cc s liu bn ngoi trong sut mt min nh tuyn OSPF. E2 l loi

tuyn ng mc nh cho cc tuyn ng hc c thng qua con ng phn phi li.

+Cc thc tin tt nht c ngh l thc hin cc tuyn ng E1 khi nhiu ASBRs

ang qung co mt tuyn ng bn ngoi vo lnh vc nh tuyn cng trnh nh

tuyn ti u, thc hin cc tuyn ng E2 khi ch c 1 ASBR l qung co mt tuyn

ng bn ngoi vo lnh vc nh tuyn.

+Cc bng nh tuyn trn RT1 v GTNT2 cho OSPF E1 v E2 tuyn qung co ca

RT3:



+Bn ngoi Type-1 (E1) cc tuyn ng lun c a thch hn loi 2 (E2) cc tuyn

ng bn ngoi. Khi c nhiu (E2) cc tuyn ng bn ngoi 2 Type-cho mng bn

ngoi tng t trong OSPF LSDB, LSA vi cc s liu E2 qung co thp nht s c

la chn v ci t vo bng nh tuyn.

+Cc s liu v pha trc (chi ph t c mt ASBR) s c xem xt khi nhiu

tuyn ng E2 c gi tr metric ging nhau. Cc show ip ospf br-router lnh hin th

cc chi ph cho mt ASBR.

+Lu : Cc s liu ni b hoc chi ph i vi cc ASBR khng c xem xt khi so

snh cc tuyn ng E2.

+ Cc bng nh tuyn v OSPF LSDB trn RT1 cho cc tuyn ng bn ngoi OSPF:



1.9.5 Type 6. Group Membership

M t quan h thnh vin nhm multicast OSPF.

+MOSPF Multicast Link State Routing bng nh tuyn l mt bn dch ca cy ng i

ngn nht. Multicast lin kt nh nc nh tuyn l mt phn m rng trc tip ca

unicast nh tuyn v s dng mt cch tip cn cy da trn ngun. Mc d unicast nh

tuyn l kh tham gia, phn m rng nh tuyn multicast l rt n gin v d hiu.

+Multicast m ng i ngn nht u tin giao thc (MOSPF) l mt phn m rng ca

giao thc OSPF s dng lin kt nh nc a nh tuyn to ra cy da trn

ngun. Giao thc i hi mt lin kt gi cp nht trng thi mi lin kt cc a ch

unicast ca mt my ch vi a ch nhm hoc a ch my ch c ti tr. Gi ny

c gi l nhm thnh vin LSA. Bng cch ny, chng ta c th bao gm trong cc cy

ch c my ch (s dng a ch unicast ca h) m thuc v mt nhm c th. Ni cch

khc, chng ti thc hin mt cy c cha tt c cc host thuc v mt nhm, nhng

chng ti s dng cc a ch unicast ca my ch trong vic tnh ton. Cho hiu qu, cc

b nh tuyn tnh cy ng i ngn nht theo yu cu (khi n nhn c cc gi tin

multicast u tin). Ngoi ra, cy c th c lu trong b nh cache s dng trong

tng lai bi cng mt ngun / cp nhm. MOSPF l mt giao thc hng d liu, ln



u tin mt b nh tuyn MOSPF thy mt gi tin vi mt ngun nht nh v a ch

nhm, cc b nh tuyn xy dng cc Dijkstra cy ng i ngn nht.

+MOSPF cung cp kh nng chuyn tip multicast gi tin t mt mng IP khc thng

qua b nh tuyn Internet. MOSPF chuyn tip mt gi tin multicast trn c s c hai

ngun v ch ca gi tin. C s d liu nh nc lin kt OSPF cung cp mt m t y

cu trc lin kt cc h thng t tr ca. Bng cch thm mt loi mi ca qung co

lin kt nh nc, cc nhm thnh vin-LSA, v tr ca tt c cc thnh vin trong nhm

multicast c xc nh chnh xc trong c s d liu. Con ng ca mt gi tin

multicast c th c tnh bng cch xy dng mt cy ngn nht-con ng c gc l

ngun ca gi tin. Tt c cc ngnh khng c thnh vin multicast c ct ta t

cy. Nhng cy ngn nht-con ng ta ban u c xy dng khi gi tin u tin

c nhn. Kt qu ca vic tnh ton ng i ngn nht l sau lu li s dng

tip theo ca gi c ngun v ch ging nhau. MOSPF c s dng trong mt h thng

t tr duy nht. Khi h tr IP multicast trn ton b Internet, MOSPF s phi c s

dng vi mt giao thc nh tuyn gia cc AS multicast nh DVMRP. Router chy

MOSPF ch hot ng trong cc mng ang s dng MOSPF nhng c th c trn ln

vi cc router OSPF khng multicast. C hai loi router c th hot ng khi chuyn tip

thng xuyn (unicast) IP lu lng d liu. Trong MOSPF, cng ging nh trong OSPF

giao thc c bn, gi d liu (multicast hay unicast) c nh tuyn "nh l", h khng

tip tc ng gi hoc decapsulated nh h chuyn cc h thng t tr.

+Hot ng: ++ Trong OSPF, mi qun l b nh tuyn hon ton c s d liu bao

gm hon chnh cu trc lin kt mng m t. Bng cch gii thiu mt loi trng thi kt

ni k lc mi - thnh vin nhmLSA - c th cho MOSPF, v tr ca tt c cc multicast

cc nt ca mt nhm multicast phi c lu tr trong c s d liu cu trc lin

kt. K t khi mt OSPF trng thi kt ni giao thc, thng tin ny do c sn trn tt

c cc router trong min c sn. Nhm LSA thnh vin c to ra bi nhng thit b

nh tuyn, m trong mt subnet ( mng LAN) thng qua IGMPxc nh thnh vin

nhm. Nhng LSA vn cn, cng nh b nh tuyn thng thng v LSA mng ch

trong vng mt khu vc OSPF, do , khng c n cc khu vc khc hoc thm ch

khc H thng t tr chuyn tip.

++Kt hp vi cc b nh tuyn thng thng v LSA mng ( cu trc lin kt c s d

liu ) do c th bt u t router, sau mt ngun multicast (source) cho mi

ngun mt Sourcebase Tree ngm - mt con ng ngn nht cy , . cy ng i ngn

nht (SPT ngn), trong c cc ngun multicast nh l ngi ch - c tnh bng cch

mng. N l b sung cho bt k giao thc nh tuyn multicast yu cu k t khi thng

thng OSPF nh tuyn unicast chia s.

+Khu vc nh tuyn:



++ OSPF cho php mt min OSPF (v d nh h thng t tr ) thnh nhiu ci gi l khu

vc phn chia. Nu iu ny c thc hin, khng cn c bt k b nh tuyn trn

mt y cu trc lin kt bn ca min OSPF. Thay vo , mi router ch bit

din tch ca n (s), trong khi cc thng tin lin lc gia cc khu vc ca ABR ( Din tch

bin gii Router ) l. Trong khi iu ny c li cho unicast OSPF, tuy nhin, l ph hp

vi multicast OSPF khng SPTS hon thnh c tnh ton. iu ny c th dn n vic

nh tuyn multicast hiu qu.

++ Do MOSPF hot ng gia hai khu vc, Router vng bin gii phi c multicast b

hnh vi ca mng li giao thng. B nh tuyn nh vy c gi l khu vc bin

gii b nh tuyn multicast (MABR). Mt MABR s tm tt tt c cc thng tin

multicast v cc LSA tng ng trong vng 0 gi (Lu : Din tch 0 khng c phn

phi thng tin nhn c ny li cho cc khu vc khc, rng phng php ny ch hu

ch nu cc ngun multicast trong khu vc l 0). Nu ngun multicast nhng cng ngoi

vng 0, vn ny bng cch thit lp mt k t i din -bit gii quyt trong cc b

nh tuyn-LSA cho mi MABR. Bit ny gy ra bt k MABR l thnh vin ca bt k

nhm multicast, lu lng multicast, v do rt ra mt ngun m khng phi l trong

cc khu vc 0 Nh vy, lu lng multicast n khu vc 0, v sau iu ny c th

chuyn tip theo thnh vin nhm c bit n trong vng 0 multicast giao thng n

cc khu vc b nh hng. Nhng iu ny c th c lu lng mng khng mong

mun (giao thng) kt qu nu khng c ngun multicast "thc s" tn ti.

1.9.6 Type 7. NSSA

M t cc tuyn n cc ch xa.

+Gii thiu:

++OSPF khu vc khng--ln mp (NSSA) tnh nng c m t bi RFC 1587 v ln

u tin c gii thiu trong Cisco IOS Software pht hnh 11.2. N l mt phn m

rng khng c quyn ca cc tnh nng khu vc cn s khai hin c, cho php tim cc

tuyn ng bn ngoi mt cch hn ch vo khu vc cn s khai. Ti liu ny gii thch

cch tnh nng NSSA hot ng.

++ Phn phi li thnh mt khu vc NSSA to ra mt loi c bit ca qung co trng

thi kt ni (LSA) c bit n nh loi 7, m ch c th tn ti trong mt khu vc

NSSA. NSSA t tr b nh tuyn ranh gii h thng (ASBR) to ra LSA ny v mt b

nh tuyn bin gii khu vc NSSA (ABR) chuyn n thnh mt loi 5 LSA, m c

truyn b vo OSPF domain. Cc s mng th hin nguyn tc ny.



+M hnh:

Trong s mng, khu vc 1 c nh ngha l mt khu vc cn s khai. Cc tuyn

ng IGRP khng c th c lan truyn n cc min OSPF v phn phi li l khng

c php vo khu vc cn s khai. Tuy nhin, nu chng ta nh ngha khu vc 1 l

NSSA, chng ta c th tim cc tuyn ng IGRP vo OSPF NSSA min vi vic to ra

loi 7 LSA. Phn phi li cc tuyn RIP khng c php vo khu vc 1 v NSSA l mt

phn m rng n khu vc cn s khai. Cc c tnh khu vc cn s khai vn cn tn ti,

trong bao gm khng c loi 5 LSA cho php.

+Mt type 7 LSA l g?y l mt loi 7 LSA c to ra bi mt ASBR NSSA. LSA

Type 5 khng c php vo khu vc NSSA, v vy NSSA ASBR to ra mt loi 7 LSA

thay vo , m vn nm trong NSSA. Loi 7 LSA c dch tr li vo mt loi 5 bi

NSSA ABR.

LS age: 36

Options: (No TOS-capability, No Type 7/5 translation, DC)

LS Type: AS External Link

Link State ID: 10.10.10.0 (External Network Number)

Advertising Router: 141.108.1.21

LS Seq Number: 80000001

Checksum: 0x4309

Length: 36

Network Mask: /24

Metric Type: 2 (Larger than any link state path)

TOS: 0

Metric: 20



Forward Address: 9.9.9.9

External Route Tag: 0

+Sn lng ny trng ging nh mt LSA bn ngoi. y l mt s c im quan trng

v kt qu ny:

++ Bit P-Bit ny c s dng ni NSSA ABR liu dch loi 7 vo loi 5.

++ Khng Hnh 7/5 dch c ngha l bit P = 0.

++ Loi 7/5 dch c ngha l bit P = 1.

++ Nu bit P = 0, sau ABR NSSA phi khng dch LSA ny vo Loi 5. iu ny xy

ra khi NSSA ASBR cng l mt ABR NSSA.

++ Nu bit P = 1, sau NSSA ABR phi dch kiu ny 7 LSA thnh mt loi 5

LSA. Nu c nhiu NSSA ABRs, l cao nht vi b nh tuyn ID.

+Nhim v cu hnh:

C hai hng v trong NSSA, ging nh trong cc lnh vc cn s khai. C NSSAs m

chn loi 5 v loi 4 LSA, nhng cho php loi 3 LSA, v c NSSA hon ton khu vc

cn s khai, m ch cho php cc tuyn ng mc nh tm tt v cc b lc tt c mi

th khc.

Defining a Not-So-Stubby Area

lm cho mt khu vc cn s khai thnh mt NSSA, lnh ny theo cu hnh OSPF:

router ospf 1

Area 1 nssa

Lnh ny phi c cu hnh trn tt c cc router duy nht trong khu vc

1. Sau khi xc nh khu vc 1 l NSSA, n phi c nhng c im:

*Khng LSA Type 5 c cho php trong khu vc 1. iu ny c ngha l khng c cc

tuyn RIP c php trong khu vc 1.

*Tt c cc tuyn IGRP c phn phi nh loi 7. 7 loi ny ch c th tn ti trong

NSSA.

*Tt c cc loi 7 LSA c quy i sang loi 5 LSA bi NSSA ABR v ang b r r

vo OSPF domain nh loi 5 LSA.

+Xc nh mt NSSA Hon ton Din tch cn s khai

cu hnh NSSA hon ton khu vc cn s khai, thc hin lnh ny theo cu hnh

OSPF:

router ospf 1

Area 1 nssa no-summary

Cu hnh lnh ny trn NSSA ch ABRs. Sau khi xc nh cc khu vc cn s khai NSSA

hon ton, khu vc 1 c nhng c im ngoi cc c im NSSA:

*Khng c loi 3 hoc 4 tm tt LSA c cho php trong khu vc 1. iu ny c ngha

l khng c cc tuyn ng lin khu vc c cho php trong khu vc 1.



*Mt tuyn ng mc nh c tim vo khu vc cn s khai NSSA hon ton nh

mt loi 3 tm tt LSA.

+Lc trong NSSA:

*C nhng tnh hung m khng cn phi tim cc tuyn ng bn ngoi vo NSSA

nh loi 7. Tnh trng ny thng xy ra khi mt ASBR cng l mt ABR NSSA. Khi

phn phi li din ra trong kch bn ny, cc b nh tuyn to ra loi 5 cng nh loi 7

LSA. Bn c th ngn chn c router t vic to ra loi 7 LSA cho NSSA vi lnh

ny:

router ospf 1

Area 1 nssa no-redistribution

*Trong s mng, khu vc 1 c cu hnh vi khng-phn phi li ty chn. iu

ny c ngha rng tt c cc tuyn IGRP c phn phi vo vng 0, nhng khng loi 7

LSA c to ra cho khu vc 1. Ch c cu hnh lnh ny trn mt ASBR NSSA cng

l mt ABR.

-Mt trng hp lc l khi bn cn phi ngn chn loi 7 LSA t c dch bn ngoi

NSSA. Ni cch khc, khi bn mun kim sot loi 7 LSA c dch sang loi 5. V d,

bn c mt RIP hc ng 141.108.10.0/24 c tim vo OSPF NSSA Khu vc 1.Bn

khng mun tuyn ng ny c tit l vo phn cn li ca khu vc OSPF. S dng

cu hnh ny trn mt trong hai NSSA ASBR hoc NSSA ABR thc hin iu ny:

router ospf 1

summary-address 141.108.10.0 255.255.255.0 not-advertise

-Cu hnh ny to ra mt loi 7 LSA m khng dch sang loi 5 bi NSSA ABR.

+Tuyn ng mc nh trong NSSA

*C hai cch c mt tuyn ng mc nh trong NSSA. Khi bn cu hnh mt khu

vc NSSA, theo mc nh NSSA ABR khng to ra mt tuyn ng tm tt mc



nh. Trong trng hp ca mt khu vc cn s khai hoc mt khu vc cn s khai

NSSA hon ton, NSSA ABR khng to ra mt tuyn ng tm tt mc nh.

+Default Summary Route

*Bng vic xc nh mt khu vc nh mt khu vc cn s khai NSSA hon ton, NSSA

ABR to ra mt tuyn ng tm tt mc nh. Nh cp, nu khu vc NSSA khng

c nh ngha l hon ton cn s khai, sau mt tuyn ng tm tt mc nh

khng c to ra bi NSSA ABR. Cu hnh ny to ra mt tuyn ng tm tt mc

nh cho mt khu vc cn s khai NSSA hon ton.

router ospf 1

Area 1 nssa no-summary

+Default Type 7

Cu hnh ny to ra mt loi tuyn ng mc nh 7. Bn c th cu hnh lnh ny trn

bt k NSSA ASBR hoc NSSA ABR vi nhng quy tc:

NSSA ASBR c th to ra mt mc nh ch khi n c mt tuyn ng

mc nh trong bng nh tuyn ca n.

Cc tuyn ng mc nh phi c bit n thng qua giao thc khng

OSPF

NSSA ABR c th to ra mt tuyn ng mc nh c hoc khng c mt

tuyn ng mc nh trong bng nh tuyn ca n.

Lnh ny c s dng to ra mt tuyn ng mc nh NSSA:

router ospf 1

Area 1 nssa default-information-originate

-Type 8. Unused: khng s dng.

-Type 9, 10, 11: s dng tnh ton cc tuyn, s dng trong k thut qun l lu lng

trong MPLS.

1.10 Qu Trnh Chn DR V BDR

Qu trnh bu chn lin quan n 2 tham s: u tin (priority) v router ID. Tham s

priority c chn trc tin, gi tr priroity nm trong khong t 0 n 255. Nu priority

t l 0 th router ny s khng tham gia vo qu trnh bu chn DR/BDR. Router no c

c u tin cao nht s c chn l DR, cao th hai s l BDR. Mc nh gi tr

priority OSPF l 1. Khi gi tr priority bng nhau th OSPF s bu chn DR da vo

tham s th hai l router ID.

Trong h thng mng dng OSPF khng cu hnh cng interface loopback th gi tr

router ID c chn l gi tr a ch IP ln nht ca cc interface ang hot ng (active



interface) ca router. Nu c cng loopback th cng loopback c chn, trng hp c

nhiu cng loopback th chn cng loopback no c a ch IP cao nht.

-DR v BDR c bu ra trong cc mng a truy nhp

-DR c cc nhim v sau:

M t mng a truy nhp v cc Router gn vo mng cho phn cn li ca lin

mng. Qun l qu trnh trn lt trong mng a truy nhp.

DR i din cho mng a truy nhp. Cc Router khc ch thit lp Adjacency vi

DR.

-BDR c bu c ra d phng cho DR. Tt c cc Router thit lp Adjacency vi c

DR v BDR. Nu

1.11 Router ID

theo di cc LSA trong LSDB, mi router u c gn mt ID nh tuyn, mt s

chm thp phn 32-bit l duy nht cho AS. Router ID xc nh cc router trong AS,

khng phi l a ch IP ca mt giao din ca router. Router ID khng c s dng nh

mt a ch IP ch gi thng tin n cc b nh tuyn. N l mt quy c ngnh

cng nghip thng s dng a ch IP ln nht hoc nh nht giao cho cc b nh tuyn

nh Router ID. V a ch IP l duy nht, c ny m bo rng cc ID Router OSPF

cng c o.

1.12 Link State

Mt giao thc nh tuyn trng thi kt ni l mt trong hai loi chnh ca giao thc nh

tuyn c s dng trong chuyn mch gi mng cho truyn thng my tnh (khc l

khong cch vector giao thc nh tuyn ). V d v cc giao thc nh tuyn trng thi

kt ni bao gm m con ng ngn nht u tin (OSPF) v h thng trung gian n h

thng trung gian (IS-IS).

Cc giao thc lin kt nh nc c thc hin bi tt c cc nt chuyn mch trong

mng (v d nh cc nt c chun b chuyn tip cc gi tin, trong Internet , chng

c gi l cc b nh tuyn ). Cc khi nim c bn ca nh tuyn trng thi kt ni l

mi nt xy dng mt bn ca cc kt ni vo mng, trong hnh thc ca mt th ,

cho thy nhng nt c kt ni m cc nt khc. Mi nt sau mt cch c lp tnh

ton tip theo hp l tt nht con ng t n n mi a im c th trong mng. B

su tp cc ng dn tt nht sau s hnh thnh ca nt bng nh tuyn .

iu ny tri ngc vi khong cch vector giao thc nh tuyn , m lm vic bng cch

mi c phn nt ca n bng nh tuyn vi cc nc lng ging. Trong mt giao thc

trng thi kt ni thng tin duy nht thng qua gia cc nt l kt ni lin quan .



1.13 M Hnh

1.14 Cc Type ca OSPF

1.14.1 R1



1.14.2 R2

1.14.3 R3



1.15 Show Ip OSPF Neighbor

1.15.1 R1



1.15.2 R2

1.15.3 R3



1.16 Show Ip OSPF Border-routers

1.16.1 R1

1.16.2 R2



1.16.3 R3

1.17 Show Ip OSPF 1

1.17.1 R1



1.17.2 R2

1.17.3 R3



1.18 Config

1.18.1 R1

!

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname R1

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

no ip icmp rate-limit unreachable

ip cef

!

!

!

!

no ip domain lookup

!

!

!

!

!

!

!

!

!

!

!

!

!



!

!

!

!

!

!

ip tcp synwait-time 5

!

!

!

!

!

interface Loopback0

ip address 1.1.1.1 255.255.255.0

!

interface FastEthernet0/0

ip address 4.4.4.1 255.255.255.0

duplex auto

speed auto

!

interface Serial0/0

ip address 5.5.5.1 255.255.255.0

clock rate 2000000

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

no ip address

shutdown

clock rate 2000000

!

!

router ospf 1



router-id 1.1.1.1

log-adjacency-changes

area 1 nssa

redistribute static subnets

network 4.4.4.0 0.0.0.255 area 1

network 5.5.5.0 0.0.0.255 area 1

!

ip forward-protocol nd

ip route 9.9.9.0 255.255.255.0 4.4.4.2

!

!

no ip http server

no ip http secure-server

!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous



line vty 0 4

login

!

!

end

1.18.2 R2

!

!

version 12.4




!

hostname R2

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5


ip cef

!

!

!

!

no ip domain lookup

!

!

!

!

!

!

!

!



!

!

!

!

!

!

!

!

!

!

!


!

!

!

!

!

interface Loopback0

ip address 2.2.2.2 255.255.255.0

!


ip address 6.6.6.2 255.255.255.0

duplex auto

speed auto

!

interface Serial0/0

ip address 5.5.5.2 255.255.255.0

clock rate 2000000

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

no ip address



shutdown

clock rate 2000000

!

!

router ospf 1

router-id 2.2.2.2


area 1 nssa

network 5.5.5.0 0.0.0.255 area 1

network 6.6.6.0 0.0.0.255 area 0

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0



exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

end

1.18.3 R3

!

!

version 12.4




!

hostname R3

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5


ip cef

!

!

!

!

no ip domain lookup

!

!

!

!

!



!

!

!

!

!

!

!

!

!

!

!

!

!

!


!

!

!

!

!

interface Loopback0

ip address 3.3.3.3 255.255.255.0

!

interface Loopback1

ip address 30.30.30.30 255.255.255.0

ip ospf network point-to-point

!

interface Loopback2

ip address 100.100.100.1 255.255.255.0

ip ospf network point-to-point

!


ip address 6.6.6.3 255.255.255.0

duplex auto

speed auto

!

interface Serial0/0



no ip address

shutdown

clock rate 2000000

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

no ip address

shutdown

clock rate 2000000

!

!

router ospf 1

router-id 3.3.3.3


area 2 nssa

network 6.6.6.0 0.0.0.255 area 0

network 30.30.30.0 0.0.0.255 area 0

network 100.100.100.0 0.0.0.255 area 2

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!



!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

end

1.18.4 R4

!

!

version 12.4




!

hostname R4

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model



memory-size iomem 5


ip cef

!

!

!

!

no ip domain lookup

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!


!

!

!

!

!

interface Loopback0

ip address 9.9.9.9 255.255.255.0

!




ip address 4.4.4.2 255.255.255.0

duplex auto

speed auto

!


no ip address

shutdown

duplex auto

speed auto

!

!


ip route 0.0.0.0 0.0.0.0 4.4.4.1

!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous



line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

end

2 NETWORK TYPES

2.1 Gii Thiu V Network Types Trong OSPF

lm vic gn nh c quyn vi Ethernet vn chuyn ton b s nghip ca ti, n

cho ti mt thi gian thc s nm bt c khi nim v mng khng pht sng. Giao

thc nh tuyn ng, c bit l OSPF, nhu cu lm quen vi tt c cc loi lp hai cu

trc lin kt, v vy ti bit ti phi cho bn thn mnh tt hn v vn ny. May

mn thay, lm vic vi Dynamips v mng frame relay o c cung cp nhng kinh

nghim ti cn thit cm thy thoi mi thc hin tt c cc loi mng OSPF khc

nhau.

OSPF media types: c 4 dng

2.2 Multicaccess

Mi trng nh Ethernet, Fast Ethernet, Gigabit Ethernet, FDDI .

Mng broadcast, OSPF s tin hnh bu chn DR, BDR gim thiu lu lng trn

mng.

Quy trnh bu chn DR v BDR bt u ngay khi router u tin c cng c bt ln

trn mng multiaccess. iu ny xy ra khi router bt ngun v cu lnh network cho

cng c cu hnh. Nu mt router gia nhp mng sau khi bu chn DR v BDR

th n s khng th tr thnh DR hoc BDR cho d n c s priority trn cng hoc

router ID cao hn router DR hoc BDR hin hnh. Chng ta phi cu hnh trn router c

s router ID cao nht trc m bo router ny s tr thnh DR

Router A c chn lm DR v c u tin cao nht. Router B c chn lm

BDR,B v C c u tin bng nhau nn BDR c chn da trn router ID cao nht l

router

B. Cc router s thit lp quan h vi DR v BDR



2.3 Point-To-Point

iu ny l bi n nay cc loi mng n gin nht, v phc v nh mt neo thun tin

t thc y cc cuc tho lun. Mt mng li im-im l, nh tn ca n kho

lo m t, mt lin kt gia hai im chnh xc (hoc router). Mt gi tin c gi t trn

cc b nh tuyn s lun lun c chnh xc mt ngi nhn vo lin kt a phng.

L mi trng truyn dn c ng gi DHLC/ppp, Framerelay/ATM point-to-point

subinterface. Khng c s bu chn DR/BDR v gi tin c gi dng Multicast.Cc

gi tin OSPF c gi i dng multicast. v d di, router A kt ni point-to- point

n cc router khc v thit lp quan h trng thi n router B, C v D.

M hnh Point-to-Point

Trong m hnh ny, mi PVC phi c nh ngha l cc point-to-point subinterface vi

cc subnet khc nhau. Khi cu hnh, khng cn ch nh network type v cc subinterface

mc nh c network type l point-to-point. Li ch ca m hnh ny l cc VC (virtual

circuit) c th cu hnh trn cng giao tip. Nhc im l lng ph nhiu khng gian a

ch cho mi kt ni point to point subinterface. Hn na kch thc ca cc LSA to bi

router A s ln hn.rt nhiu v phi cha Type 3 stub link cho mi kt ni point to

point.

Cu hnh Point-to-Point Subinterface

RouteA#

interface Serial 0.1 point-to-point

ip address 141.108.1.1 255.255.255.252



!

interface Serial 0.2 point-to-point

ip address 141.108.1.5 255.255.255.252

2.4 Broadcast

R rng, kt ni point-to-point khng quy m tt. Mt cch hiu qu hn ca kt ni mt

s lng ln cc thit b thc hin mt multiaccess phn khc, l mt phn khc c

th c truy cp bi nhiu im cui. Mt phn on Ethernet l mt v d ca mt

mng li nh vy.

Ethernet mng li h tr chng trnh pht sng ; mt gi tin truyn qua mt thit b c

th c nhn vi trung bnh (trong trng hp ny mt Switch) mi im kt thc

khc s nhn c mt bn sao. y l thun li khng ch tit kim bng thng, m cn

to thun li cho hng xm pht hin t ng.

Trong v d hnh trn, R1 c th multicast (pht sng ch dnh cho thnh gi nht nh)

mt cho OSPF tin nhn lin kt, bit rng tt c cc OSPF router khc kt ni vi cc

lin kt s nhn c n v tr li vi thng ip multicast ring ca h. Do , cc nc

lng ging c th nhanh chng nhn ra nhau v hnh thc k cn m khng bit a ch

trc . M khng phi l thun tin

OSPF router trn mt phn khc multiaccess s bu ra mt router ch nh (DR) v sao

lu nh tuyn c ch (BDR) m tt c cc b nh tuyn khng c ch nh s to

thnh mt k. iu ny l m bo rng cc s k cn duy tr khng pht trin qu ln,

mt phn khc c cha mi router s yu cu 45 k cn to thnh mt li, nhng

ch c 17 khi mt DR v BDR c a ra.

2.5 Non-Broadcast

Tht khng may, khng phi tt c cc cng ngh multiaccess h tr truyn pht

sng. Frame relay v ATM c l l v d ph bin nht ca giao thng vn ti khng pht

sng, i hi c nhn mch o c nh (PVC) c cu hnh gia cc im kt thc.



Thng bo trong cc cu trc lin kt chuyn tip khung hnh trn, R1 phi to ra v

truyn ti mt gi tin c nhn cho tt c cc im n ng mun tip cn.Bn cnh l

khng khip khng hiu qu i vi bng thng vi, hn ch ny i hi cc b nh

tuyn bit a ch ca cc nc lng ging ca mnh trc khi ng c th giao tip vi

h.

OSPF c th hot ng theo mt trong hai phng thc trn mt mng khng pht sng:

khng pht sng a truy cp (NBMA) hoc im-a im. Mi mt trong cc cu trc

lin kt khc phc nhng trng hp khng c kh nng pht sng t mt hng khc.

Khng pht sng a truy cp (NBMA)

Mt phn khc NBMA m phng chc nng ca mt mng li pht sng. Tt c cc

router trn phn khc phi c cu hnh vi a ch IP ca mi nc lng ging. OSPF

xin cho cc gi tin c c nhn sau c truyn nh cc gi tin unicast cho mi

ngi hng xm lin k.

Nh trong mt mng li pht sng thc, mt DR v BDR c bu hn ch s lng

k cn thnh.

2.6 OSPF Broadcast Network

Trong mi trng mng OSPF Broadcast c mt vi vn ny sinh nh sau:

-Hello c gi ra tm kim neighbor

-Mt router s phi thit lp neighbor vi tt c cc router cn li

-S lng adjacencies tng t l thun vi s lng routers hin c

-S lng gi tin LSAs c gi ra cng tng ln nhanh chng so vi s lng router

hin c.



Tt c cc iu trn u dn n hin tng router b qu ti, bng thng mng b chim

dng rt nhiu.

khc phc tnh trng trn, mt gii php a ra l bu chn mt router lm i din

cho OSPF network ni chuyn vi cc routers trong mng. Router ny c gi l

Designated Router.



2.7 Designated Router and Backup Designated Router

DR l router c la chn lm i din cho mng. ROuter ny c nhim v chnh l duy

tr thng tin ca h thng mng cc routers khc truy xut. DR c hai chc nng

chnh:

-Thit lp neighbor vi ton b cc routers trong mng

-L mt router i din gi cc thng bo cho mng

DR c nhim v l thu thp v gi i cc thng tin (LSAs) trong h thng mng.

BDR l mt router c tnh d phng cho DR, khi DR khng hot ng c na th BDR

s chim quyn v tr thnh DR ca h thng

-BDR cng ging nh DR, tin hnh thit lp neighbor vi tt c cc router khc

-BDR khng gi v cng ko nhn thng tin (LSAs) trong h thng mng

BDR c mt b m thi gian khi theo di DR bit chc rng DR vn ang hot ng

tt. Nu ht khong thi gian ny m DR khng tr li li cho BDR th BDR s coi

DR cht v tin hnh chim quyn tr thnh DR ca h thng.

Sau khi bu chn DR, BDR th tt c cc routers trong h thng s thit lp neighbor

vi 2 router ny.

DR s dng bn tin LSA type 2 - network LSA qung b v h thng mng ln a ch

multicast 224.0.0.5. Cc routers khc s gi thng tin ln 224.0.0.6 truyn ti trc tip

vi DR.



2.8 Election Of DR/BDR

Khi mt router khi ng mt tin trnh OSPF, n s lng nghe cc Hellos t cc routers

khc. Nu ht dead interval m khng nhn c Hello no, n s t nng mnh ln l

DR.

Nu cc Hellos c nhn trc khi ht dead interval, router no c OSPF priority cao

hn s lm DR. Tng t vi vic bu chn BDR. Nu 1 router c priority bng 0 s loi

khi qu trnh bu chn DR.

Nu 2 routers c priority bng nhau, router no c Router ID ln hn s bu lm DR.

Tng t vi BDR.



Mt khi DR c la chn, qu trnh bu chn s khng th thc hin li cho n khi

DR hoc BDR down. iu c ngha l, nu nh c mt router vi priority cao hn

c boot ln th vn s khng xy ra vic chim quyn DR. Khi DR down, BDR s

t ng c a ln lm DR, sau th qu trnh bu chn BDR mi s din ra.

Mc nh, vi thit b ca CIsco th gi tr priority l 1. Gi tri ny c th thay i trn

interface tham gia vo OSPF.

2.9 Point-To-Multipoint

Mt cu hnh im-a tip cn gii hn khng pht sng mt cch khc nhau. Thay v c

gng cnh tranh vi kh nng pht sng, n tm cch t chc PVC thnh mt tp hp

cc mng im-im. Xin cho cc gi tin vn phi c nhn rng v ly truyn qua

ng ring cho mi ngi hng xm, nhng cch tip cn a cung cp hai li th ring

bit: khng c DR / BDR l cn thit, v cc lin kt im-im m phng c th chim

mt subnet



2.10 Mi Trng Truyn Dn Nh Framerelay, ATM,X.25.

Cu hnh dng 1, 3, 5 th bn phi cho interface broadcast i. Nu mi trng no c

bu chn DR, BDR th cc a ch multicast s c s dng l 224.0.0.5 v 224.0.0.6 .

Nu trong frame-relay th ta c th cu hnh broadcast v khng broadcast tng ng vi

lnh:R1(config-if)#frame-relay map ip 192.168.1.1 102

R1(config-if)#frame-relay map ip 192.168.1.1 102 broadcast.

Vi OSPF mode th ta c th cem int dng mode no bng cch Show ip ospf

interface.

OSPF mode ch c tc dng khi tao cu hnh cng tham gia dnh tuyn OSPF.

R1# sh ip ospf interface

Serial0/0 is up, line protocol is down

Internet address 192.168.1.1/24, Area 0

ProcessID 1, Router ID 1.1.1.1, Network Type

Point-to-Point-Multicast, Cost: 64.

Hai OSPF mode khc nhau c th thit lp c neihbors vi nhau nhng cha chc trao

i thng tin cho nhau c.

Vd: point-to-multipoint v broadcast.

Ring OSPF mode point-to-multipoint non-broadcast v point-to-multipoint c th thit

lp neighbor v trao i vi nhau v: Bn no c ch broadcast th n s gi hello bng

multicast 224.0.0.5. Bn no khng c kh nng khm ph th i con kia gi hello th

n s gi li bng unicat.



2.11 Mo Hnh

2.12 Config

2.12.1 R1

!

!

version 12.4




!

hostname R1

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

ip cef

!

!

!



!

no ip domain lookup

ip domain name lab.local

!

!

!

!

interface Loopback0

ip address 1.1.1.1 255.255.255.0

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/0

ip address 192.168.1.36 255.255.255.0

encapsulation frame-relay

ip ospf network broadcast

serial restart-delay 0

clock rate 2000000

frame-relay map ip 192.168.1.37 122 broadcast



!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

no ip address

shutdown

clock rate 2000000

!



interface Serial0/2

no ip address

shutdown

clock rate 2000000

!

interface Serial0/3

no ip address

shutdown

clock rate 2000000

!

!

router ospf 1


network 192.168.1.36 0.0.0.0 area 0

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0



exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

End.

2.12.2 R2

!

!

version 12.4




!

hostname R2

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

ip cef

!

!

!

!

no ip domain lookup


!



!

!

!

!

interface Loopback0

ip address 2.2.2.1 255.255.255.0

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/0

ip address 192.168.23.36 255.255.255.0

encapsulation ppp


clock rate 2000000

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

ip address 192.168.1.37 255.255.255.0



ip ospf priority 0

clock rate 2000000


frame-relay map ip 192.168.1.39 221


!

!

router ospf 1




network 192.168.1.37 0.0.0.0 area 0

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

End



2.12.3 R3

!

!

version 12.4




!

hostname R3

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

ip cef

!

!

!

!

no ip domain lookup


!

!

!

!

!

!

!

!

interface Loopback0

ip address 3.3.3.1 255.255.255.0

!


no ip address



shutdown

duplex auto

speed auto

!

interface Serial0/0

ip address 192.168.23.37 255.255.255.0

encapsulation ppp

clock rate 2000000

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

no ip address

shutdown

clock rate 2000000

!

interface Serial0/2

no ip address

shutdown

clock rate 2000000

!

interface Serial0/3

no ip address

shutdown

clock rate 2000000

!

!


!

!

no ip http server


!



!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

End

2.12.4 R4

!

!

version 12.4




!



hostname R4

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

ip cef

!

!

!

!

no ip domain lookup


!

!

!

!

!

interface Loopback0

ip address 4.4.4.1 255.255.255.0

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/0

ip address 192.168.1.39 255.255.255.0



ip ospf priority 0

clock rate 2000000






!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

ip address 192.168.45.36 255.255.255.0

encapsulation ppp


clock rate 2000000

!

!

router ospf 1


network 192.168.1.39 0.0.0.0 area 0

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!



!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

login

!

!

End

2.12.5 R5

!

!

version 12.4




!

hostname R5

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

ip cef

!

!

!



!

no ip domain lookup


!

!

!

!

!

interface Loopback0

ip address 5.5.5.1 255.255.255.0

!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/0

ip address 192.168.1.40 255.255.255.0



ip ospf priority 0


clock rate 2000000




!


no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/1

ip address 192.168.45.37 255.255.255.0

encapsulation ppp




clock rate 2000000

!

!

router ospf 1


network 192.168.1.40 0.0.0.0 area 0

!


!

!

no ip http server


!

!

!

!

!

control-plane

!

!

!

!

!

!

!

!

!

!

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous



line vty 0 4

login

!

!

End

lsa & network types

Documents