From: David Buechner (dbuechn@attglobal.net)
Date: Tue Feb 25 2003 - 16:47:11 GMT-3
To follow up to my question from yesterday:
First, someone asked for relevant configuration information from R2 which I
have included below.
Second, I've gotten a couple of responses like Annu Roopa's which said:
>I think in the first case when u do IBGP full mesh all
>the routers including R2,R5,R6 get two routes from R1
>and R3 and then they decide the best path (*>).
>
>But when u are doing the RR case Router R6 gets two
>paths as seen and decides the best path for the
>networks.R6 will advertise only the best path to its
>clients R2 and R5 and hence they have only 1 path the
>best path of R6. What do u think ? Am i correct in
>understanding ? someone care to comment.
If this is true, then it seems like the Route Reflector is of much less use
that I would otherwise believe. Cisco doc and Doyle Vol 2 (among other
places) give me the idea that a route reflector cluster (properly
configured) is a functional replacement for the same group of routers with
full-mesh IBGP. So far I believe I've not gotten the "properly configured"
part of this right yet - although if I'm mis-understanding the purpose of
route reflectors here please tell me! Thanks to those who have responded
so far - my apologies if I'm being dense!
Below is output from my R2 as well as yesterday's note for reference.
Thanks!
David
R2#sh ip bgp 172.16.0.0
BGP routing table entry for 172.16.0.0/24, version 2
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
254
151.100.2.254 (metric 20) from 131.1.6.6 (131.1.6.6)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 131.1.3.3, Cluster list: 131.1.6.6
R2#sh ip bgp
BGP table version is 9, local router ID is 131.1.2.2
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
*>i172.16.0.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.1.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.2.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.3.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.4.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.5.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.6.0/24 151.100.2.254 0 100 0 254 i
*>i172.16.7.0/24 151.100.2.254 0 100 0 254 i
R2#sh running-config | begin router bgp
router bgp 400
no synchronization
bgp log-neighbor-changes
neighbor internal peer-group
neighbor internal remote-as 400
neighbor internal update-source Loopback0
neighbor 131.1.6.6 peer-group internal
no auto-summary
!
At 04:15 pm 2/24/2003 -0500, I wrote:
>Hi all!
>
>I have a BGP route reflector issue on the following network:
>
>
>--- (E1) --- R7 (AS 254) --- (E0) ---
>| |
>| |
>R3 (AS 400) R1 (AS 400)
>| |
>| |
>------------ R6 (AS 400) ------------
> | \
> | \-- R5 (AS 400)
> |
> R2 (AS 400)
>
>R7 is simulating a "backbone" router which is advertising several networks
>to R1 and R3. If I set up a full mesh between all of the AS 400 routers
>(i.e. R1, R2, R3, R5, R6) then I get the results I would expect - each
>router has two entries in the BGP table for each advertised network. The
>route with the "closest" next-hop is then entered in the main IP routing
>table (where distance to the next-hop is determined by the IGP - OSPF in
>this case). If I try to set this up as a Route Reflector cluster with all
>routers peering with R6 I do NOT get the results I expect. Instead, what
>I get is that R2 and R5 only have one entry for each network in their BGP
>table which corresponds to the "best" one chosen by R6.
>
>Any ideas what I'm missing here? Thanks!
>
>David
>
>
>R6#sh ip bgp 172.16.0.0
>BGP routing table entry for 172.16.0.0/24, version 2
>Paths: (2 available, best #2, table Default-IP-Routing-Table)
> Advertised to non peer-group peers:
> 131.1.1.1 131.1.2.2 131.1.5.5
> 254, (Received from a RR-client)
> 10.0.1.207 (metric 20) from 131.1.1.1 (150.100.35.1)
> Origin IGP, metric 0, localpref 100, valid, internal
> 254, (Received from a RR-client)
> 151.100.2.254 (metric 20) from 131.1.3.3 (131.1.3.3)
> Origin IGP, metric 0, localpref 100, valid, internal, best
>R6#sh ip bgp
>BGP table version is 9, local router ID is 131.1.6.6
>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
>* i172.16.0.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.1.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.2.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.3.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.4.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.5.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.6.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>* i172.16.7.0/24 10.0.1.207 0 100 0 254 i
>*>i 151.100.2.254 0 100 0 254 i
>R6#sh running-config
>Building configuration...
>
>router bgp 400
> no synchronization
> bgp always-compare-med
> bgp log-neighbor-changes
> neighbor 131.1.1.1 remote-as 400
> neighbor 131.1.1.1 update-source Loopback0
> neighbor 131.1.1.1 route-reflector-client
> neighbor 131.1.2.2 remote-as 400
> neighbor 131.1.2.2 route-reflector-client
> neighbor 131.1.3.3 remote-as 400
> neighbor 131.1.3.3 update-source Loopback0
> neighbor 131.1.3.3 route-reflector-client
> neighbor 131.1.5.5 remote-as 400
> neighbor 131.1.5.5 update-source Loopback0
> neighbor 131.1.5.5 route-reflector-client
> maximum-paths 2
> no auto-summary
>!
This archive was generated by hypermail 2.1.4 : Sat Mar 01 2003 - 11:06:35 GMT-3