Thanks for your reply. I now knew what is going on inside of R3. Thanks.
BTW, I attached my R3's BGP config again. (You are true that I attached R2's BGP config) I think your copy/paste R3's BGP config is incorrect. It seems to be R2's BGP config… But according to the output you gave and the others router's config, I guess R3 is a route-reflector for R2 and R4. If so, here is what happen: R1 sends update about 3.3.1.0/24 to R2 and R4. R2 and R4 send them to all their iBGP peers (here only R3). R3 selects the best path as being through R2. R3 acts as route-reflector and advertise the best NLRI to R4. It does not advertise R4's NLRI to R2 because it is not the best one. When you shut the interface between R1 and R2 down, R2 ask to R3 to withdraw NLRI to 3.3.1.0/24. R3's best path is now through R4. Therefore, it advertises it to R2. R3#show run Building configuration... Current configuration : 1828 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R3 ! boot-start-marker boot-end-marker ! ! no aaa new-model memory-size iomem 5 ip cef ! ! ! ! no ip domain lookup ! multilink bundle-name authenticated ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! archive log config hidekeys ! ! ! ! ! ! ! ! interface Loopback0 ip address 3.3.3.3 255.255.255.0 ip ospf network point-to-point ! interface FastEthernet0/0 no ip address shutdown duplex auto speed auto ! interface Serial0/0 no ip address encapsulation frame-relay clock rate 2000000 ! interface Serial0/0.32 point-to-point ip address 3.3.23.3 255.255.255.0 snmp trap link-status frame-relay interface-dlci 302 ! interface Serial0/0.34 point-to-point ip address 3.3.34.3 255.255.255.0 snmp trap link-status frame-relay interface-dlci 304 ! interface FastEthernet0/1 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 log-adjacency-changes network 3.3.3.3 0.0.0.0 area 0 network 3.3.23.3 0.0.0.0 area 0 network 3.3.34.3 0.0.0.0 area 0 ! router bgp 2 no synchronization bgp log-neighbor-changes network 3.3.3.0 mask 255.255.255.0 neighbor R2R4 peer-group neighbor R2R4 remote-as 2 neighbor R2R4 update-source Loopback0 neighbor R2R4 route-reflector-client neighbor 3.3.2.2 peer-group R2R4 neighbor 3.3.4.4 peer-group R2R4 no auto-summary ! On Tue, Jan 31, 2012 at 9:15 AM, Christophe Lemaire < [email protected]> wrote: > Hi, > > I think your copy/paste R3's BGP config is incorrect. It seems to be R2's > BGP config… > > But according to the output you gave and the others router's config, I > guess R3 is a route-reflector for R2 and R4. > > If so, here is what happen: > R1 sends update about 3.3.1.0/24 to R2 and R4. > R2 and R4 send them to all their iBGP peers (here only R3). > R3 selects the best path as being through R2. > R3 acts as route-reflector and advertise the best NLRI to R4. It does not > advertise R4's NLRI to R2 because it is not the best one. > > When you shut the interface between R1 and R2 down, R2 ask to R3 to > withdraw NLRI to 3.3.1.0/24. R3's best path is now through R4. Therefore, > it advertises it to R2. > > Regards, > Christophe > > On 30 Jan 2012, at 17:24, kyujin Choi wrote: > > > I have this topology. From R1, show ip bgp result is below. *Every bgp > > route is coming from 3.3.12.2 or 3.3.14.4.* > > > > > > > > [image: bgp.jpg]< > https://learningnetwork.cisco.com/servlet/JiveServlet/showImage/2-208950-88940/bgp.jpg > > > > > > > > > > R1#sh ip bgp > > > > BGP table version is 14, local router ID is 3.3.1.1 > > > > Status codes: s suppressed, d damped, h history, * valid, > best, i - > > internal, > > > > r RIB-failure, S Stale > > > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > > > > > Network Next Hop Metric LocPrf Weight Path > > > > *> 3.3.1.0/24 0.0.0.0 0 32768 i > > > > * 3.3.2.0/24 3.3.14.4 0 2 i > > > > *> 3.3.12.2 0 0 2 i > > > > * 3.3.3.0/24 3.3.14.4 0 2 i > > > > *> 3.3.12.2 0 2 i > > > > * 3.3.4.0/24 3.3.14.4 0 0 2 i > > > > *> 3.3.12.2 0 2 i > > > > R1# > > > > > > > > > > > > From R3, it shows same result. For 3.3.1.0, it uses 3.3.4.4 or 3.3.2.2 > > > > > > > > R3#sh ip bgp > > > > BGP table version is 22, local router ID is 3.3.3.3 > > > > Status codes: s suppressed, d damped, h history, * valid, > best, i - > > internal, > > > > r RIB-failure, S Stale > > > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > > > > > Network Next Hop Metric LocPrf Weight Path > > > > * i3.3.1.0/24 3.3.4.4 0 100 0 1 i > > > > *>i 3.3.2.2 0 100 0 1 i > > > > r>i3.3.2.0/24 3.3.2.2 0 100 0 i > > > > *> 3.3.3.0/24 0.0.0.0 0 32768 i > > > > r>i3.3.4.0/24 3.3.4.4 0 100 0 i > > > > R3# > > > > > > > > > > > > *However, I have one problem. As you can see below, R2 can only see > 3.3.1.0 > > through 3.3.12.1* > > > > > > > > > > > > R2#show ip bgp > > > > BGP table version is 7, local router ID is 3.3.2.2 > > > > Status codes: s suppressed, d damped, h history, * valid, > best, i - > > internal, > > > > r RIB-failure, S Stale > > > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > > > > > Network Next Hop Metric LocPrf Weight Path > > > > *> 3.3.1.0/24 3.3.12.1 0 0 1 i > > > > *> 3.3.2.0/24 0.0.0.0 0 32768 i > > > > r>i3.3.3.0/24 3.3.3.3 0 100 0 i > > > > r>i3.3.4.0/24 3.3.4.4 0 100 0 i > > > > R2# > > > > > > > > *But, I can see both routes from R4 for 3.3.1.0* > > > > > > > > R4#sh ip bgp > > > > BGP table version is 7, local router ID is 3.3.4.4 > > > > Status codes: s suppressed, d damped, h history, * valid, > best, i - > > internal, > > > > r RIB-failure, S Stale > > > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > > > > > Network Next Hop Metric LocPrf Weight Path > > > > * i3.3.1.0/24 3.3.2.2 0 100 0 1 i > > > > *> 3.3.14.1 0 0 1 i > > > > r>i3.3.2.0/24 3.3.2.2 0 100 0 i > > > > r>i3.3.3.0/24 3.3.3.3 0 100 0 i > > > > *> 3.3.4.0/24 0.0.0.0 0 32768 i > > > > R4# > > > > > > > > > > > > > > > > R2#show ip bgp 3.3.1.0 > > > > BGP routing table entry for 3.3.1.0/24, version 2 > > > > Paths: (1 available, best #1, table Default-IP-Routing-Table) > > > > Advertised to update-groups: > > > > 2 > > > > 1 > > > > 3.3.12.1 from 3.3.12.1 (3.3.1.1) > > > > Origin IGP, metric 0, localpref 100, valid, external, best > > > > R2# > > > > > > > > > > > > > > > > > > > > R4#sh ip bgp 3.3.1.0 > > > > BGP routing table entry for 3.3.1.0/24, version 2 > > > > Paths: (2 available, best #2, table Default-IP-Routing-Table) > > > > Advertised to update-groups: > > > > 2 > > > > 1 > > > > 3.3.2.2 (metric 129) from 3.3.3.3 (3.3.3.3) > > > > Origin IGP, metric 0, localpref 100, valid, internal > > > > Originator: 3.3.2.2, Cluster list: 3.3.3.3 > > > > 1 > > > > 3.3.14.1 from 3.3.14.1 (3.3.1.1) > > > > Origin IGP, metric 0, localpref 100, valid, external, best > > > > R4# > > > > > > > > (question) > > > > *If I shut down interface from R1 which is connected to R2, it shows up > > right away. Why couldn't i see before 3.3.4.4 from R2 for show ip bgp > > 3.3.1.0?* > > > > > > > > > > > > > > > > R2#show ip bgp 3.3.1.0 > > > > BGP routing table entry for 3.3.1.0/24, version 0 > > > > Paths: (1 available, no best path) > > > > Not advertised to any peer > > > > 1 > > > > *3.3.4.4 (metric 129) from 3.3.3.3 (3.3.3.3)* > > > > Origin IGP, metric 0, localpref 100, valid, internal > > > > Originator: 3.3.4.4, Cluster list: 3.3.3.3 > > > > R2# > > > > > > > > > > > > R2#show ip bgp > > > > BGP table version is 7, local router ID is 3.3.2.2 > > > > Status codes: s suppressed, d damped, h history, * valid, > best, i - > > internal, > > > > r RIB-failure, S Stale > > > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > > > > > Network Next Hop Metric LocPrf Weight Path > > > > **>i3.3.1.0/24 3.3.4.4 0 100 0 1 i* > > > > *> 3.3.2.0/24 0.0.0.0 0 32768 i > > > > r>i3.3.3.0/24 3.3.3.3 0 100 0 i > > > > r>i3.3.4.0/24 3.3.4.4 0 100 0 i > > > > R2# > > > > > > > > > > > > ---------------------- R1 R2 R3 R4 config -------------------------- > > > > > > > > > > > > R1#sh run > > Building configuration... > > > > Current configuration : 1523 bytes > > ! > > 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 > > ip cef > > ! > > ! > > ! > > ! > > no ip domain lookup > > ! > > multilink bundle-name authenticated > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > archive > > log config > > hidekeys > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > > > ! > > interface Loopback0 > > ip address 3.3.1.1 255.255.255.0 > > > > > > ! > > interface FastEthernet0/0 > > no ip address > > shutdown > > duplex auto > > speed auto > > > > > > ! > > interface Serial0/0 > > no ip address > > encapsulation frame-relay > > clock rate 2000000 > > > > ! > > interface Serial0/0.12 point-to-point > > ip address 3.3.12.1 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 102 > > ! > > interface Serial0/0.14 point-to-point > > ip address 3.3.14.1 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 104 > > ! > > interface FastEthernet0/1 > > 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 bgp 1 > > no synchronization > > bgp log-neighbor-changes > > network 3.3.1.0 mask 255.255.255.0 > > neighbor 3.3.12.2 remote-as 2 > > neighbor 3.3.14.4 remote-as 2 > > no auto-summary > > ! > > ip forward-protocol nd > > ! > > ! > > no ip http server > > no ip http secure-server > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > control-plane > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > line con 0 > > exec-timeout 0 0 > > logging synchronous > > line aux 0 > > line vty 0 4 > > login > > ! > > ! > > end > > > > R1# > > > > > > > > > > > > > > > > > > > > R2#sh run > > Building configuration... > > > > Current configuration : 1765 bytes > > ! > > version 12.4 > > service timestamps debug datetime msec > > service timestamps log datetime msec > > no service password-encryption > > ! > > hostname R2 > > ! > > boot-start-marker > > boot-end-marker > > ! > > ! > > no aaa new-model > > memory-size iomem 5 > > ip cef > > ! > > ! > > ! > > ! > > no ip domain lookup > > ! > > multilink bundle-name authenticated > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > archive > > log config > > hidekeys > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > > > ! > > interface Loopback0 > > ip address 3.3.2.2 255.255.255.0 > > ip ospf network point-to-point > > ! > > > > > > interface FastEthernet0/0 > > no ip address > > shutdown > > duplex auto > > speed auto > > > > > > ! > > interface Serial0/0 > > no ip address > > encapsulation frame-relay > > clock rate 2000000 > > ! > > interface Serial0/0.21 point-to-point > > > > > > ip address 3.3.12.2 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 201 > > ! > > interface Serial0/0.23 point-to-point > > ip address 3.3.23.2 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 203 > > ! > > interface FastEthernet0/1 > > 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 > > log-adjacency-changes > > passive-interface Serial0/0.21 > > > > > > network 3.3.2.2 0.0.0.0 area 0 > > network 3.3.12.2 0.0.0.0 area 0 > > network 3.3.23.2 0.0.0.0 area 0 > > ! > > router bgp 2 > > no synchronization > > bgp log-neighbor-changes > > network 3.3.2.0 mask 255.255.255.0 > > neighbor 3.3.3.3 remote-as 2 > > neighbor 3.3.3.3 update-source Loopback0 > > neighbor 3.3.12.1 remote-as 1 > > no auto-summary > > ! > > ip forward-protocol nd > > ! > > ! > > no ip http server > > no ip http secure-server > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > control-plane > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > line con 0 > > exec-timeout 0 0 > > logging synchronous > > line aux 0 > > line vty 0 4 > > login > > ! > > ! > > end > > > > R2# > > > > > > > > ---------------- > > > > > > > > > > > > R3#sh run > > Building configuration... > > > > Current configuration : 1856 bytes > > ! > > version 12.4 > > service timestamps debug datetime msec > > service timestamps log datetime msec > > no service password-encryption > > ! > > hostname R3 > > ! > > boot-start-marker > > boot-end-marker > > ! > > ! > > no aaa new-model > > memory-size iomem 5 > > ip cef > > ! > > ! > > ! > > ! > > no ip domain lookup > > ! > > multilink bundle-name authenticated > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > archive > > log config > > hidekeys > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > > > ! > > interface Loopback0 > > ip address 3.3.3.3 255.255.255.0 > > ip ospf network point-to-point > > ! > > > > > > interface FastEthernet0/0 > > no ip address > > shutdown > > duplex auto > > speed auto > > > > > > ! > > interface Serial0/0 > > no ip address > > encapsulation frame-relay > > clock rate 2000000 > > ! > > interface Serial0/0.32 point-to-point > > > > > > ip address 3.3.23.3 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 302 > > ! > > interface Serial0/0.34 point-to-point > > ip address 3.3.34.3 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 304 > > ! > > interface FastEthernet0/1 > > 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 > > > > log-adjacency-changes > > > > network 3.3.2.2 0.0.0.0 area 0 > > > > network 3.3.23.2 0.0.0.0 area 0 > > > > ! > > > > router bgp 2 > > > > no synchronization > > > > bgp log-neighbor-changes > > > > network 3.3.2.0 mask 255.255.255.0 > > > > neighbor 3.3.3.3 remote-as 2 > > > > neighbor 3.3.3.3 update-source Loopback0 > > > > neighbor 3.3.3.3 next-hop-self > > > > neighbor 3.3.12.1 remote-as 1 > > > > no auto-summary > > ! > > ip forward-protocol nd > > ! > > ! > > no ip http server > > no ip http secure-server > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > control-plane > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > line con 0 > > exec-timeout 0 0 > > logging synchronous > > line aux 0 > > line vty 0 4 > > login > > ! > > ! > > end > > > > > > > > > > > > -------------------- > > > > > > > > R4#sh run > > Building configuration... > > > > Current configuration : 1765 bytes > > ! > > version 12.4 > > service timestamps debug datetime msec > > service timestamps log datetime msec > > no service password-encryption > > ! > > hostname R4 > > ! > > boot-start-marker > > boot-end-marker > > ! > > ! > > no aaa new-model > > memory-size iomem 5 > > ip cef > > ! > > ! > > ! > > ! > > no ip domain lookup > > ! > > multilink bundle-name authenticated > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > archive > > log config > > hidekeys > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > interface Loopback0 > > ip address 3.3.4.4 255.255.255.0 > > > > ip ospf network point-to-point > > ! > > > > > > interface FastEthernet0/0 > > no ip address > > shutdown > > duplex auto > > speed auto > > > > > > ! > > interface Serial0/0 > > no ip address > > encapsulation frame-relay > > clock rate 2000000 > > ! > > interface Serial0/0.41 point-to-point > > ip address 3.3.14.4 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 401 > > ! > > interface Serial0/0.43 point-to-point > > ip address 3.3.34.4 255.255.255.0 > > snmp trap link-status > > frame-relay interface-dlci 403 > > ! > > interface FastEthernet0/1 > > 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 > > > > log-adjacency-changes > > > > network 3.3.4.4 0.0.0.0 area 0 > > > > network 3.3.34.4 0.0.0.0 area 0 > > > > ! > > > > router bgp 2 > > > > no synchronization > > > > bgp log-neighbor-changes > > > > network 3.3.4.0 mask 255.255.255.0 > > > > neighbor 3.3.3.3 remote-as 2 > > > > neighbor 3.3.3.3 update-source Loopback0 > > > > neighbor 3.3.3.3 next-hop-self > > > > neighbor 3.3.14.1 remote-as 1 > > > > no auto-summary > > > > ! > > ip forward-protocol nd > > ! > > ! > > no ip http server > > no ip http secure-server > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > control-plane > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > ! > > line con 0 > > exec-timeout 0 0 > > logging synchronous > > line aux 0 > > line vty 0 4 > > login > > ! > > ! > > end > > > > R4# > > _______________________________________________ > > For more information regarding industry leading CCIE Lab training, > please visit www.ipexpert.com > > > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
