BGP - iBGP over an IGP Lab

Is this Jeff Doyle's mistake or mine? Here is an interesting point that I found when doing Case Study iBGP over IGP Lab in TCP/IP Routing II.This is my routing configuration

Aspen#show run | begin router

router ospf 100

log-adjacency-changes

network 192.168.1.196 0.0.0.3 area 0

network 192.168.1.220 0.0.0.3 area 0

Vail#show run | begin router

ospf 100

log-adjacency-changes

redistribute bgp 100 subnets !redistribute routes into OSPF so these routes will be advertised to Telluride

network 192.168.1.220 0.0.0.3 area 0

!

router bgp 100

synchronization

bgp log-neighbor-changes

network 192.168.1.200 mask 255.255.255.252 !all of these networks have to be configured on this router so these routes will

be distributed into Tahoe & Taos

network 192.168.1.208 mask 255.255.255.252

network 192.168.1.224 mask 255.255.255.252

network 192.168.50.0

network 192.168.75.0

neighbor 192.168.1.197 remote-as 100

neighbor 192.168.1.210 remote-as 300

neighbor 192.168.1.225 remote-as 200

no auto-summary

Telluride#show run | begin router

router ospf 100

log-adjacency-changes

redistribute bgp 100 subnets

network 192.168.1.196 0.0.0.3 area 0

!

router bgp 100

synchronization

bgp log-neighbor-changes

network 192.168.1.204 mask 255.255.255.252

network 192.168.1.212 mask 255.255.255.252

network 192.168.1.216 mask 255.255.255.252

network 192.168.100.0

network 192.168.200.0

network 192.168.250.0

neighbor 192.168.1.205 remote-as 400

neighbor 192.168.1.221 remote-as 100

no auto-summary

Taos#show run | begin router

router bgp 200

no synchronization

bgp log-neighbor-changes

network 192.168.1.216 mask 255.255.255.252

network 192.168.100.0

network 192.168.200.0

neighbor 192.168.1.226 remote-as 100

no auto-summary

Alta#show run | begin router

router bgp 400

no synchronization

bgp log-neighbor-changes

network 192.168.1.200 mask 255.255.255.252

network 192.168.50.0

network 192.168.75.0

neighbor 192.168.1.206 remote-as 100

no auto-summary

Tahoe#sho run | begin router

router bgp 300

no synchronization

bgp log-neighbor-changes

network 192.168.1.212 mask 255.255.255.252

network 192.168.250.0

neighbor 192.168.1.209 remote-as 100

no auto-summary

According to Jeff, we don't need to define which networks that Vail & Telluride need to advertised to other eBGP peer (Tahoe, Taos, Alta) using network command. However, I found that without defining these networks, Vail & Telluride will not automatically advertise them to their eBGP peers. I can verify my above config as:

Alta#show ip bgp

BGP table version is 20, local router ID is 192.168.75.1

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

*> 192.168.1.200/30 0.0.0.0 0 32768 i

r> 192.168.1.204/30 192.168.1.206 0 0 100 i

*> 192.168.1.208/30 192.168.1.206 0 100 i

*> 192.168.1.212/30 192.168.1.206 1 0 100 i

*> 192.168.1.216/30 192.168.1.206 1 0 100 i

*> 192.168.1.224/30 192.168.1.206 0 100 i

*> 192.168.50.0 0.0.0.0 0 32768 i

*> 192.168.75.0 0.0.0.0 0 32768 i

*> 192.168.100.0 192.168.1.206 1 0 100 i

*> 192.168.200.0 192.168.1.206 1 0 100 i

*> 192.168.250.0 192.168.1.206 1 0 100 i

Alta#show ip route

Codes: C - connected, S - static, 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

i - IS-IS, su - IS-IS summary, 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

C 192.168.75.0/24 is directly connected, Loopback1

B 192.168.200.0/24 [20/1] via 192.168.1.206, 00:08:17

B 192.168.250.0/24 [20/1] via 192.168.1.206, 00:08:17

C 192.168.50.0/24 is directly connected, Loopback0

192.168.1.0/30 is subnetted, 6 subnets

B 192.168.1.224 [20/0] via 192.168.1.206, 00:09:17

C 192.168.1.200 is directly connected, Loopback2

C 192.168.1.204 is directly connected, Serial1/0

B 192.168.1.216 [20/1] via 192.168.1.206, 00:08:17

B 192.168.1.208 [20/0] via 192.168.1.206, 00:09:17

B 192.168.1.212 [20/1] via 192.168.1.206, 00:08:17

B 192.168.100.0/24 [20/1] via 192.168.1.206, 00:08:17

Alta#ping 192.168.250.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.250.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 136/181/212 ms

Can anyone help me to verify this?