[c-nsp] IPv6 in IPv4 BGP?

[Bruce Pinsky]

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Arnold Nipper wrote:
> On 06.03.2006 20:53 Hank Nussbacher wrote
> 
>> Is this normal or a bug?  Peer 2001:798:1D:10AA::1 pops up in IPv4 and
>> IPv6 output.
>>
> 
> Actually BGP doesn't care which protocol you are using to carry your
> routing information. Same like IS-IS ...
> 
> use
> 
> router bgp ...
>  address-family ipv4
>  no neighbor 2001:798:1D:10AA::1 activate
> 
> 

Well, it does to the extent that the nexthop in the NLRI must be from the
same address family.  So to carry IPv4 routes in a IPv6 peering session,
you are going to have to manually set the nexthop via a route-map since
there is no method for mapping the IPv6 neighbor address back into an IPv4
nexthop address:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/ipv6_c/sa_bgpv6.htm#wp1046742

No such problem with IPv6 routes in IPv4 peering sessions since the IPv4
peering address can converted to IPv6 nexthop address via an IPv4-mapped
address on the router:


router bgp 65000
 no bgp default ipv4-unicast
 neighbor 192.168.99.70 remote-as 65000
 !
 address-family ipv6
 neighbor 192.168.99.70 activate
 network 2001:0DB8:FFFF::/48

Router> show ipv6 route
IPv6 Routing Table - 10 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
B 2001:0DB8:DDDD::/64 [200/0]
  via ::FFFF:192.168.99.70, IPv6
...

Also, if you want to use an IPv4 peering session for only IPv6 routing
information, you need to be sure to disable the default advertising of IPv4
routes via the "no bgp default ipv4-unicast" command.

- --
=========
bep

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