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salve, ho un problema. ho 3 router in cascata:

R1 -> R2 -> R3 ( il router R1 ed R3 non sono collegati direttamente tra loro.)

ho configurato il BGP in tutti e tre i router con AS 10 su tutti e tre.
R3 annuncia le sue network a R2 ma R2 non le annuncia a R1.
vi posto le conf

R3
router bgp 10
no synchronization
bgp log-neighbor-changes
network 172.16.0.0 mask 255.255.255.0
network 192.168.100.0
network 192.168.170.0
network 192.168.200.0
neighbor 172.16.0.2 remote-as 10
no auto-summary

R2

router bgp 10
no synchronization
bgp log-neighbor-changes
network 10.0.0.0 mask 255.255.255.0
network 172.16.0.0 mask 255.255.255.0
neighbor 10.0.0.1 remote-as 10
neighbor 172.16.0.3 remote-as 10
maximum-paths 2
no auto-summary

R1

router bgp 10
no synchronization
bgp log-neighbor-changes
network 10.0.0.0 mask 255.255.255.0
neighbor 10.0.0.2 remote-as 10
no auto-summary

le network 10.0.0.0/24 e 172.16.0.0/24 sono le network delle interfacce che collegano direttamente i router

in questo lab vogli ke le network di R3 arrivino ad R1.(pultroppo si fermano su R2 e non vanno oltre.)

vi posto uno sh ip route
R1#sh ip ro
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 1 subnets
B 172.16.0.0 [200/0] via 10.0.0.2, 00:14:05
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, FastEthernet0/0

in R1 mancano le network 192.168.100.0 192.168.170.0 192.168.200.0

anche R1 e R3 devono essere "vicini". o R2 deve essere un route-reflector.
o devi usare le confederazioni. o usi diversi AS per R1-R2 e R2-R3 se vuoi.

l'IBGP, per default, non fa quello che vuoi.

Emiliano ha scritto: Oltre a quello che ti ha detto ghira puoi anche provare a inserire come neighbor di r1 il router r3 e viceversa.

Io intendevo esattamente quello. "vicini" nel senso bgp del termine. con IBGP
tutti devono essere vicini di tutti se non usi route-reflector o confederation.

Why is there a problem with iBGP in large networks? How can this problem be solved? Describe each solution in 1 - 3 sentences.

There must be a full mesh of iBGP sessions, in other words: each BGP router within an AS must have iBGP sessions with all other BGP routers in the AS. By requiring that all information in iBGP is learned directly from the router that learned the information over eBGP, there can't be any loops in iBGP. The full mesh requirement can be solved using either route reflectors or confederations.

Route reflectors distribute iBGP information from one router to another, which is normally not allowed in iBGP. Since the clients of the route reflector get all iBGP from the route reflector they don't need to have iBGP sessions with all other BGP routers. Reflectors add additional path attributes that allow them to detect and eliminate loops.

In a confederation, the AS is split into a number of sub-ASes, so the iBGP full mesh is done within each sub-AS and a modified version of eBGP is used between sub-ASes. To the outside, the confederation behaves like a single AS.

e se necessario, ricordati di usare "next-hop-self"

http://www.cisco.com/en/US/tech/tk365/t ... 95bb.shtml