IBGP over IGP

Posted in NETWORKING/IP ROUTING by edeguzman on October 3, 2007

This configuration is one of the router within the AS 100. Basically on the laboratory there are 3 routers present within the AS. Two routers serve as the Border Gateway, each of them runs a BGP process and at the same time an OSPF process runs as its IGP. One of the Border Gateway is connected to a stub AS and the other Border Gateway is connected by two stub AS. The other router within the AS just runs an OSPF connecting the two Border Gateway.

Below is the configuration of one of the border gateway.

interface Loopback0
ip address 192.168.255.254 255.255.255.255
!
interface Ethernet0/0
ip address 192.168.1.221 255.255.255.252
!
interface Ethernet0/1
ip address 192.168.1.193 255.255.255.252
!
interface Serial1/0
ip address 192.168.1.226 255.255.255.252
no fair-queue
clockrate 64000
!
interface Serial1/1
ip address 192.168.1.209 255.255.255.252
clockrate 64000
!
interface Serial1/2
no ip address
shutdown
!
interface Serial1/3
no ip address
shutdown
!
router ospf 100
redistribute bgp 100 subnets
network 192.168.1.193 0.0.0.0 area 0
network 192.168.1.221 0.0.0.0 area 0
network 192.168.255.254 0.0.0.0 area 0
!
router bgp 100
timers bgp 3 9
neighbor 192.168.1.210 remote-as 300
neighbor 192.168.1.210 default-originate
neighbor 192.168.1.225 remote-as 200
neighbor 192.168.255.253 remote-as 100
neighbor 192.168.255.253 update-source Loopback0
neighbor 192.168.255.253 next-hop-self
!
ip classless
no ip http server
!
!
!
line con 0
transport input none
line aux 0
line vty 0 4
password passkey
login
!
end

Neighbor 192.168.255.253 update-source Loopback0 – this command simply causes the BGP messages to be sourced from the IP address of the loopback interface rather than from the physical interface. Without this command, the TCP source of the TCP sessions would be the outgoing interface and not the loopback interface.

timers bgp 3 9 – this command basically change the time of the keepalive message
being send to a peer and the holddown time. 3 is the keepalive message and 9 is the holddown time.

neighbor 192.168.1.210 default-originate – this command simply advertise a default-
route to the neighboring peer.

The other commands are already explained from my previous post. I got heavy day thats why I felt tired. This one is quick post in one of configuration I did for the day.

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