[c-nsp] ME3600 BGP Route-Maps and IPv6 (WAS: Re: preference on bgp route advertisements)

[Gert Doering]

Hi,

On Thu, Mar 08, 2012 at 03:30:16PM +1100, Reuben Farrelly wrote:
> No - as opposed to having no route-map matching IPv6 at all.
> 
> So, if I have a route-map that (after my correction) actually matches an 
> IPv6 route at the top of the route-map sequence and sets the community 
> value of that IPv6 matched route, then it works as expected.
> 
> If I have a route-map that parses IPv6 routes, but does not match any 
> IPv6 routes (no match ipv6 ... defined anywhere in any of the route-map 
> sequence entries) then it matches on the first _IPv4_ route map entry 
> and sets the community of that IPv6 route to the IPv4 match instead. 
> That's the bug :)

As far as I have interpreted this behaviour: for an IPv6 route, the
"match ip" statements are just not evaluated, as if "not there at all",
and vice versa for IPv4 routes and "match ipv6".

So you could do something like:

route-map foo permit 10
  match ip address prefix-list foov4
  match ipv6 address prefix-list foov6
  set community 1234:456

if both match statements were applied, this wouldn't match anything ever,
and so only the corresponding AFI matches are used.  So, "feature", not
bug :-)


OTOH, we don't use this in practice, but have separate route-maps for
IPv4 and IPv6 - not because it wouldn't work, but it's somewhat easier
to see "which applies where?", and also because there might be differences
in routing policy ("prefer AS X over uplink Z" might not be needed for
IPv4, but not make sense for IPv6)

gert
-- 
USENET is *not* the non-clickable part of WWW!
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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