STATIC NULL0 ROUTE

Hello experts,

 

I'm working in BGP home lab, I do want to clarify that the use of static NULL 0 route.

 

There is loopback interfaces in two iBGP domain

172.16.64.1/24 in R1, 172.16.32.1/24 in R2 and the network between two iBGP routers  is 172.16.1.0/64

 

When I advertise 172.16.64.0 and 172.16.32.0 into BGP, from the eBGP side can't find these networks by using show ip bgp 

But after I run ip route 172.16.0.0 255.255.0.0 null 0 from iBGP side and advertise 172.16.0.0, I can find the 172.16.0.0 in eBGP side.

Please explain me the use of NULL0 static route why it need ?

 

Thanks in advance,[:D]

Comments

  • peetypeety ✭✭✭

    Great job labbing this up so you can see things first-hand. When you say "I advertise 172.16.64.0 and 172.16.32.0 into BGP", how are you accomplishing this?

    My suspicion, without seeing your configs yet, is that you had a network statement for 172.16.0.0/16, and you were hoping your loopbacks and inter-router link would advertise because they're in that network. BGP is, for better and worse, very particular about its network statements, and they must be an exact match for the BGP route to be generated. You could also explore 'aggregate-address' to have the router create the /16 aggregate route if any longer route exists within it.

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