Monday, February 20, 2006

 

BGP prefix advertisement problem. (Question #19)

Consider the following router configured to run BGP. Here is some relevant configuration from the router

interface Ethernet0/0
 ip address 10.1.3.1 255.255.255.252
 no keepalive
!
router bgp 300
 no synchronization
 bgp log-neighbor-changes
 network 10.1.3.0 mask 255.255.255.0
 neighbor 10.1.1.1 remote-as 100
 neighbor 10.1.2.1 remote-as 200
 no auto-summary

and "show ip route" from the router shows the following

Gateway of last resort is not set

     10.0.0.0/30 is subnetted, 3 subnets
C       10.1.3.0 is directly connected, Ethernet0/0
C       10.1.2.0 is directly connected, Serial3/0
C       10.1.1.0 is directly connected, Serial2/0

It is seen that this router's BGP neighbors are not learning the route to 10.1.3.0/24 in spite of the fact that this router is advertising that prefix. What is the problem here? How can it be fixed?

# posted by Cisco da Gama @ 1:07 PM
Comments:
Yup, that will do the trick.
# posted by Blogger Cisco da Gama : Tue Feb 21, 08:23:00 AM 2006
 
How about changing network (under router bgp 300) 10.1.3.0 mask 255.255.255.0 to
network 10.1.3.0 mask 255.255.255.252 and then adding

aggregate-address 10.1.3.0 255.255.255.0 summary-only


Would this also be a solution?
# posted by Anonymous Anonymous : Mon Feb 27, 10:01:00 PM 2006
 
Yes, that will result in the desired behavior also.
# posted by Blogger Cisco da Gama : Tue Feb 28, 02:00:00 PM 2006
 
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