From: Simon Baxter (Simon.Baxter@xxxxxxxxxxxxxx)
Date: Fri Aug 25 2000 - 11:36:53 GMT-3
They Sub-ASs don't have to be meshed. Remember the idea of confederations
is to reduce peering and make each of the confed group members behave like
EBGP peers.
If you do want to fully mesh them, although I don't believe you would want
to, yes - you'd need to use ebgp-multihop as the "outside" peers aren't
directly connected to each other.
Hop this helps...
Simon
-----Original Message-----
From: Alejandro Cadarso [mailto:a.cadarso@uniway-tec.com]
Sent: Saturday, August 26, 2000 12:31 AM
To: ccielab
Subject: BGP Confederations
Hi All,
Let's say we have three sub-ASes 1031, 1034 and 1039 connected sequencially
like this:
(AS1031)---(AS1034)---(AS1099)
They are part of the BGP confederation 100.
I know that within the subAS, all the BGP routers need to be fully meshed.
Cool.
1.- It is required to fully mesh the sub-ASes, that is do I have configure
EBGP peers between AS1031 and AS1099
also ?
I think it is not required, but I wanted to confirm, in my lab everything
seems to go Ok:
3640-1031#sh ip bgp summ
BGP router identifier 190.19.15.209, local AS number 1031
BGP table version is 5, main routing table version 5
1 network entries and 1 paths using 133 bytes of memory
1 BGP path attribute entries using 52 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP activity 2/15 prefixes, 3/2 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
State/PfxRcd
190.19.15.65 4 1034 281 280 5 0 0 00:19:09 1
3640-1031#sh ip bgp
BGP table version is 5, local router ID is 190.19.15.209
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 190.1.0.0 192.19.18.1 0 100 0 (1034 1099) i
I'm a little bit confused because the only sample configuration I could find
about confeds
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/icsbgp4.htm#xtocid27651
40
>!Router C
>router bgp 65050
>bgp confederation identifier 500
>bgp confederation peers 65060 65070
>neighbor 128.213.10.1 remote-as 65050
>neighbor 128.213.20.1 remote-as 65050
>neighbor 128.210.11.1 remote-as 65060
>neighbor 135.212.14.1 remote-as 65070
>neighbor 5.5.5.5 remote-as 100
It seems to indicate that you need peering between every Sub-AS, assuming
this:
I wasn't able to establish a peering session without the command:
neighbor 135.212.14.1 ebgp-multihop
I think it's logical, because it's an eBGP session, but I can't understand
how this sample configuration from Cisco (the only one
you could find in its Documentation) misses it.
2.- If you have peering between every Sub-AS then you have redundant
information for each route and I think it could cause some
problem because the best route is the one you have from your multihop
peering.
3640-1031#sh ip bgp summ
BGP router identifier 190.19.15.209, local AS number 1031
BGP table version is 8, main routing table version 8
1 network entries and 2 paths using 169 bytes of memory
2 BGP path attribute entries using 104 bytes of memory
2 BGP AS-PATH entries using 48 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP activity 2/25 prefixes, 5/3 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
State/PfxRcd
190.19.15.65 4 1034 315 316 8 0 0 00:53:29 1
190.19.15.66 4 1099 20 21 8 0 0 00:12:54 1
3640-1031#sh ip bgp
BGP table version is 8, local router ID is 190.19.15.209
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 190.1.0.0 192.19.18.1 0 100 0 (1099) i
* 192.19.18.1 0 100 0 (1034 1099) i
3.- Finally, if a router is part of a confederation and has no other
connections other to a member of it's own Sub-AS in the
conferedation, do you still need to configure the confederation identifier
and which are its confederation peers Sub-ASs??
Alejandro
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