From: Theodore TZEVELEKIS (theodore_tzevelekis@xxxxxxxxx)
Date: Mon May 21 2001 - 13:54:56 GMT-3
They are actually removed locally as soon as the TCP
connection dies (after a certain timeout actually).
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On
Behalf Of
Darren Hosking
Sent: Monday, May 21, 2001 3:26 PM
To: 'mcaplan.cs@clearstream.com'; ccielab@groupstudy.com
Subject: RE: should all IBGP neighbours have all EBGP paths?
I cleared the IBGP AS and I did see WITHDRAWN updates coming
through on the
router with higher local preference (didn't see the other
router sending
them - used debug ip bgp update). So if the link to the ISP
via r1 with
higher local preference goes down, IBGP will update this
router (r1) with
the routes from r2? Are these routes requested by one router
or sent by the
other?
Thanks, Darren
Configs are as follows:
r1 (primary link):
router bgp 65000
no synchronization
bgp log-neighbor-changes
neighbor 10.0.1.1 remote-as 1221
neighbor 10.0.1.1 ebgp-multihop 255
neighbor 10.0.1.1 route-map SET_OUTBOUND_TRAFFIC in
neighbor 10.0.1.1 filter-list 10 out
neighbor 172.24.96.1 remote-as 65000
neighbor 172.24.96.1 next-hop-self
ip as-path access-list 10 permit ^$
route-map SET_OUTBOUND_TRAFFIC permit 10
set local-preference 300
r2 (backup link):
router bgp 65000
no synchronization
bgp log-neighbor-changes
neighbor 10.0.2.1 remote-as 1221
neighbor 10.0.2.1 route-map SET_OUTBOUND_TRAFFIC in
neighbor 10.0.2.1 filter-list 10 out
neighbor 172.24.24.1 remote-as 65000
neighbor 172.24.24.1 next-hop-self
ip as-path access-list 10 permit ^$
route-map SET_OUTBOUND_TRAFFIC permit 20
set local-preference 250
-----Original Message-----
From: mcaplan.cs@clearstream.com
[mailto:mcaplan.cs@clearstream.com]
Sent: Monday, 21 May 2001 7:07:PM
To: dhosking@commander.com.au; ccielab@groupstudy.com;
zhutong@ronghai.com.cn
Subject: RE: should all IBGP neighbours have all EBGP paths?
Darren,
I cant tell without diagrams and configs, but I suspect its
a case of BGP
only advertises the best path.
Consider the following example
r3----------------r4 AS2
| |
++++++++++++++++++++++
| |
| |
r1-----------------r2 AS1
If R2 has the better local preference to AS2, it will tell
R1 about it. R1
will then decide that R2 is the best route to AS2. Any route
that R1 had
advertised to R2 as a route to AS2 will be then withdrawn.
If you use 'debug
ip bgp updates' you can actually see this WITHDRAWN message
being sent.
After that R2 will only have a single route to AS2 in the
BGP table. R1
however will probably have 2 routes in its BGP table - the
best one via R2
and the other via R3.
Hope this helps
Mark
> ----------
> From: zhutong[SMTP:zhutong@ronghai.com.cn]
> Reply To: zhutong
> Sent: Montag, 21. Mai 2001 08:02
> To: Darren Hosking; ccielab@groupstudy.com
> Subject: Re: should all IBGP neighbours have all EBGP
paths?
>
> Give your config pls.
>
> ----- Original Message -----
> From: "Darren Hosking" <dhosking@commander.com.au>
> To: <ccielab@groupstudy.com>
> Sent: Monday, May 21, 2001 11:44 AM
> Subject: should all IBGP neighbours have all EBGP paths?
>
>
> > I have 2 BGP routers connected externally to the same AS
and internally
> to
> > each other using IBGP. The local preference is set to
prefer one link
> over
> > the other. All paths are visible on the non-preferred
router (shows both
> > paths out with the other as preferred), however, the
router with the
> > preferred path to the ISP only shows the paths it knows
about and not
> the
> > paths via the other link.
> >
> > Is this correct? Don't both need all paths or are they
exchanged when
> the
> > preferred path is no longer available (could be a lot of
traffic)?
> >
> > I'm using Halabi 1st edition as reference, is the 2nd
edition much
> better
> > and in what areas (ie should I buy the newer edition).
> >
> > Thanks, Darren
> >
> > The output of sh ip bgp summ and sh ip bgp for one
network is shown
> below.
> >
> > Neighbor V AS MsgRcvd MsgSent TblVer InQ
OutQ Up/Down
> > State/PfxRcd
> > 10.0.1.1 4 1221 6221 3628 43815 0
0 2d12h
> 6606
> > 172.24.24.1 4 65000 6626 6313 43815 0
0 13:10:59
> 6606
> >
> > BGP table version is 43789, local router ID is
172.24.97.1
> > 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
> > *>i9.3.4.0/24 172.24.24.1 300
0 1221 ?
> > * 10.0.1.1 250
0 1221 ?
> >
> > Neighbor V AS MsgRcvd MsgSent TblVer InQ
OutQ Up/Down
> > State/PfxRcd
> > 10.0.2.1 4 1221 43026 26728 37714 0
0 4d01h
> 6605
> > 172.24.96.1 4 65000 11860 12348 37714 0
0 13:10:26
> 0
> > <---?????
> >
> > BGP table version is 37689, local router ID is
172.24.23.1
> > 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
> > *> 9.3.4.0/24 10.0.2.1 300
0 1221 ?
> > **Please
read:http://www.groupstudy.com/list/posting.html
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