From: perkinsr@WellsFargo.COM
Date: Mon Sep 09 2002 - 20:47:01 GMT-3
I was just starting to see that point. I must have missed this in the basic
BGP reading, BGP will only pass on the best path to peers? I was under the
impression that all routes were always passed along unless an AS sees its
own AS number. I was looking at the symmetry of the design and expecting a
symmetrical results, but R7 forwards R13s route on to R14 because it is the
best path, but R14s routes aren't forwarded on to R13 as they suck,
relatively speaking.
Thanks for pointing that out,
Ray
-----Original Message-----
From: Brian Dennis [mailto:brian@5g.net]
Sent: Monday, September 09, 2002 4:34 PM
To: perkinsr@WellsFargo.COM; ccielab@groupstudy.com
Subject: RE: BGP
If R7 selects R13 as the best path over R14, why would R7 send R14's
routes to R13?
Brian Dennis, CCIE #2210 (R&S/ISP Dial)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
perkinsr@WellsFargo.COM
Sent: Monday, September 09, 2002 3:17 PM
To: ccielab@groupstudy.com
Subject: BGP
Here is a simple scenario for trying some basic BGP testing:
R7
/ \
R13 R14
R13 and R14 both have the networks 10.10.10.0 and 11.11.11.0 and
12.12.12.0
as loopbacks and are redistributing to R7. R13 is using redis conn and
R14
is using network statements. Once R13 forms a peer relationship with R7
it
sees both its routes and the R14's routes, but R14s go away after about
a
minute and I only see R13s routes in the BGP table of R13. R7 always
sees
both sets of routes.
Here are the configs:
(AS is same as router number)
router bgp 7
bgp log-neighbor-changes
network 10.10.10.0 mask 255.255.255.0 backdoor
neighbor 13.13.13.13 remote-as 13
neighbor 14.14.14.14 remote-as 14
router bgp 13
bgp log-neighbor-changes
redistribute connected
neighbor 13.13.13.7 remote-as 7
no auto-summary
router bgp 14
bgp log-neighbor-changes
network 10.10.10.0 mask 255.255.255.0
network 11.11.11.0 mask 255.255.255.0
network 12.12.12.0 mask 255.255.255.0
neighbor 14.14.14.7 remote-as 7
neighbor 14.14.14.7 route-map test out
route-map test permit 10
set as-path prepend 45 62 75 38
R7#b
BGP table version is 16, local router ID is 14.14.14.7
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
*> 10.10.10.0/24 13.13.13.13 0 0 13 ?
* 14.14.14.14 0 0 14 45 62 75
38
i
*> 11.11.11.0/24 13.13.13.13 0 0 13 ?
* 14.14.14.14 0 0 14 45 62 75
38
i
*> 12.12.12.0/24 13.13.13.13 0 0 13 ?
* 14.14.14.14 0 0 14 45 62 75
38
i
*> 13.13.13.0/24 13.13.13.13 0 0 13 ?
R7#
R13 after routes disapear:
R13#b
BGP table version is 5, local router ID is 12.12.12.12
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
*> 10.10.10.0/24 0.0.0.0 0 32768 ?
*> 11.11.11.0/24 0.0.0.0 0 32768 ?
*> 12.12.12.0/24 0.0.0.0 0 32768 ?
*> 13.13.13.0/24 0.0.0.0 0 32768 ?
R13#
R13, shortly after a clear ip bgp *, before routes diapear:
R13#b
BGP table version is 8, local router ID is 12.12.12.12
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
*> 10.10.10.0/24 0.0.0.0 0 32768 ?
* 13.13.13.7 0 7 14 45 62
75
38 i
*> 11.11.11.0/24 0.0.0.0 0 32768 ?
* 13.13.13.7 0 7 14 45 62
75
38 i
*> 12.12.12.0/24 0.0.0.0 0 32768 ?
* 13.13.13.7 0 7 14 45 62
75
38 i
*> 13.13.13.0/24 0.0.0.0 0 32768 ?
R13#
R14#b
BGP table version is 12, local router ID is 12.12.12.12
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
* 10.10.10.0/24 14.14.14.7 0 7 13 ?
*> 0.0.0.0 0 32768 i
* 11.11.11.0/24 14.14.14.7 0 7 13 ?
*> 0.0.0.0 0 32768 i
* 12.12.12.0/24 14.14.14.7 0 7 13 ?
*> 0.0.0.0 0 32768 i
*> 13.13.13.0/24 14.14.14.7 0 7 13 ?
R14#
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