RFC 5549 - IPv4 Routes with IPv6 next-hop - Does it really exists?

Wed Jul 29 13:51:55 UTC 2020

Douglas Fischer writes:
> And today, I reached on https://tools.ietf.org/html/rfc5549
[...]
> But the questions are:
> There is any network that really implements RFC5549?

We've been using it for more than two years in our data center networks.
We use the Cumulus/FRR implementation on switches and FRR on Ubuntu on
servers.

> Can anyone share some information about it?

Sure.  We found the FRR/Cumulus implementation very easy to set up.  We
have leaf/spine networks interconnecting hundreds of servers (IPv4+IPv6)
with very minimalistic configuration.  In particular, you generally
don't have to configure neighbor addresses or AS numbers, because those
are autodiscovered.  I think we're basically following the
recommendations in the "BGP in the Data Center" book including the "BGP
on the Host" part (though our installation predates the book, so there
might be some differences).

The network has been working very reliably for us, so we never really
had anything to debug.  If you're coming from a world where you used
separate BGP sessions to exchange IPv4 and IPv6 reachability
information, then the operational commands take a little getting used
to, but in the end I find it very intuitive.

For example, here's one of the "show bgp ... summary" commands on a leaf
switch:

    leinen at sw-f:mgmt-vrf:~$ net show bgp ipv6 uni sum
    BGP router identifier 10.1.1.46, local AS number 65111 vrf-id 0
    BGP table version 96883
    RIB entries 1528, using 227 KiB of memory
    Peers 54, using 1041 KiB of memory
    Peer groups 2, using 128 bytes of memory

    Neighbor           V       AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
    sw-o(swp16)        4    65108  953559  938348        0    0    0 03w5d00h          688
    sw-m(swp18)        4    65108  885442  938348        0    0    0 03w5d00h          688
    s0001(swp1s0.3)    4    65300  748971  748977        0    0    0 03w5d00h            1
    s0002(swp1s1.3)    4    65300  661787  661794        0    0    0 03w1d23h            1
    s0003(swp1s2.3)    4    65300  748970  748977        0    0    0 03w5d00h            1
    s0004(swp1s3.3)    4    65300  661868  661875        0    0    0 03w1d23h            1
    s0005(swp2s0.3)    4    65300  748970  748976        0    0    0 03w5d00h            1
    [...]

Note the host names/interface names - this is how you generally refer to
neighbors, rather than using literal (IPv6) addresses.

Otherwise it should look very familiar if you have used vendor C's
"industry-standard CLI" before.

(In case you're wondering, the first two neighbors in the output are
spine switches, the others are servers.)

Cheers,
-- 
Simon.