summarize loopback addresses

[maher]

Hi there,

Just wondering about summurizing loopback address in the core network. Can we do that ? Why do we need to summarize and why not ? I also would like to know the implication if we have multiple ares (IGP using OSPF), how do we do that?

Because I found some notes in the presentation regarding "do not summurize loopback addresses in the core.

thanks.

maher

[Georg Pauwen · Accepted solution]

Hello Maher,

which presentation are you referring to ?

In general, if the Loopback addresses are advertised, they can be summarized, I do not really see a problem.

It would be helpful to know in what context that presentation talks about not summarizing loopbacks...

Regards,

GP

[maher]

Hi Gpauwen,

Thanks for the info.I'm actually refering to MPLS/VPN context. BTW, if without the concern of MPLS/VPN, how do we summarizing loopback addresses?

thanks again.

maher

[Harold Ritter]

Just assign the loopback IP addresses from the same address range as all the other interfaces and summarize as usual. Nothing special.

Hope this helps,

[Harold Ritter · Accepted solution]

In a context of MPLS VPN, you really don't want to summarize the IP addresses of your loopback interfaces since this definitely breaks the LSPs between your PEs.

Hope this helps,

[maher]

Hi Hritter,

Thanks for the info.BTW, if we summurization being done at route-reflector, would it definitely breaks the LSPs between PEs?

thanks in advance.

maher

[Harold Ritter · Accepted solution]

You can't summarize anywhere between the PEs.The LSP is setup per prefix. As soon as you change the prefix via summarizarion, you break the LSP.

This doesn't mean you can't summarize in the SP core. What people usually do is they assign loopback addresses from a different IP address range and they summarize for all address ranges but this one.

Hope this helps,