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New Member

Recursion Against IPv4+Labels prefix learned via iBGP


Due to a number of reasons we have a rather unique requirement to use IPv4+labels as a means to install a BGP next-hop against which other labelled BGP routes can be resolved.  Though this sounds fairly complex I was hoping to acheive this as follows, (basic example):

R1 (loop0 = a, loop1 = b) <---- -----> R2 (loop0 = y, loop1 = z)

There is an IGP session between R1 and R2, whereby loop0 and the inter-link are inserted into the IGP, a BGP IPv4 + labels session is established between loop0's (a and y), over this session R1 advertises b --> R2, and R2 advertises z --> R1.  Using route-maps, further labelled prefixes advertised between R1 and R2 have the BGP next-hop modified to b and z respectively.

Everything looks as I would expect, labels advertised / received as I would expect, (RIB entires etc), however, CEF shows recursion issues.  I have tried various IOS images but same (or similar) behaviour.

Should this work.. All CCO references to IPv4+labels (unless related to IPv6 prefix / path distribution) explicitly state eBGP IPv4+labels, but our requirement is for IPv4+labels in conjuction with iBGP.

(If I try a similar schema using LDP - this works fine, but unfortunately LDP is not an option in the production network).

Also note, the link between devices is Ethernet,

I can appreciate why this may not work, but conversely I see no reason (except implementation) why this will not work.

Can someone please confirm whether this should work, and if so which version of IOS for the C7200.

Thanks.  Simon

Everyone's tags (2)
New Member

Re: Recursion Against IPv4+Labels prefix learned via iBGP

Now works fine with a static mpls bindings for a and y, set to phy intf address(s) with implicit-null.

Cisco Employee

Re: Recursion Against IPv4+Labels prefix learned via iBGP

Hi Simon,

BGP IPv4 + Labels relies on a MPLS aware core (BGP free core usually) so you need a label associated to your loopback 0. You used static mapping but LDP will do the job as well.



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