LDP Address List TLV

[g.rodegari]

Hi guys,

a simple question:

How can I filter an interface to be included in the advertisement, in the field "Address List TLV" (RFC-3036) of the LDP packet sent to the neighbors?

I do not want that interfaces without LDP enabled are included in this list.

Any Help is really appreciated!

Thank you so much.

Best Regards,

Graz.

[Harold Ritter]

This is not possible. The router will include all interface addresses for all interfaces in up/up state. May I ask why you want to do this.

Thanks,

[g.rodegari]

Hi Harold,

Suppose to have thousands of subscribers interface without MPLS enabled... what is the reason why to advertise these?

Thank you,

Graz.

[mheusinger]

Hi,

those interface IPs could potentially be next hops in the neighbors routing table. The list translates to: "Dear neighbor, if you have any of the following IP addresses as next hop for a prefix in your routing table then use my labels.".

The underlying reason is, that the LDP ID of the advertising router is usually different from the IP next hop address in the neighbors routing table. Without the additional info building the LFIB could be impossible for the neighbor router.

Hope this helps! Please rate all posts.

Regards, Martin

[g.rodegari]

Ok,

but if I'm sure that there aren't feasible next-hop (subscribers side)... isn't there a way to block the advertisement?

Thank you,

Graz.

[mheusinger · Accepted solution]

Hi,

from RFC3036:

" To enable LSRs to map between a peer LDP identifier and the peer's addresses, LSRs advertise their addresses using LDP Address and Withdraw Address messages."

There seems to be no case of "conditional adress advertisement" forseen in the RFC. So the observed behaviour is RFC compliant, but might be unwanted in your case.

The only option I see is to send a feature request towards Cisco or to start an IETF discussion/draft RFC allowing this.

I totally agree, that it would make a lot of sense in your case.

Regards, Martin