From: Herbert Maosa (asawilunda@googlemail.com)
Date: Sat Aug 11 2007 - 13:43:34 ART
Yes, to an eBGP peer the default is to change the next hop. However, when
the network is multi-access, this default behaviour changes and the next hop
is not changed even to an eBGP peer.
Herbert.
On 8/11/07, NITIN NITIN <ccie_study_123@yahoo.com> wrote:
>
> Hi ,
>
> Thanks for reply
> please suggest why R2 is selcted and notr R1
> wht is criteria for this ??
> and I thought next-hop-self is for ibgp peers ----is it valid option for
> ebgp peers also.....coz to ebgp peer automatically next hop is changed (
> peering ip-address) when update go
>
> Thanks
>
>
> *Herbert Maosa <asawilunda@googlemail.com>* wrote:
>
> Hi,
>
> BGP does not change the next hop on a Multi-access network unless
> explicitly configured to do so through *next-hop self*. If the BGP speaker
> determines that both the sending and the intended neighbor are reached
> through the same interface, it leaves the next hop unchanged for optimum
> routing ( needless to make an extra unneccessary hop through this router )
> as these neighbors can reach each other directly on the multi-access
> network.
>
>
> Herbert.
>
>
> On 8/11/07, NITIN NITIN <ccie_study_123@yahoo.com> wrote:
> >
> > Hi experts,
> >
> >
> > R5 and R1 and R2 are in a broadcast domain
> > next hop is 152.1.125.2 for routes via R1
> > DON't know why
> > Please suggest ????????
> >
> > R5 - 152.1.125.5 ip
> > R1 - 152.1.125.1 ip
> > R2 - 152.1.125.2 ip
> >
> >
> >
> > Rack1R5#sh ip bgp regexp _254$
> > BGP table version is 14, local router ID is 150.1.5.5
> > Status codes: s suppressed, d damped, h history, * valid, > best, i -
> > internal,
> > r RIB-failure, S Stale
> > Origin codes: i - IGP, e - EGP, ? - incomplete
> > Network Next Hop Metric LocPrf Weight Path
> > * 205.90.31.0 152.1.125.2 0 200 254 ?
> > *> 152.1.125.2 0 200 254 ?
> > * 220.20.3.0 152.1.125.2 0 200 254 ?
> > *> 152.1.125.2 0 200 254 ?
> > * 222.22.2.0 152.1.125.2 0 200 254 ?
> > *> 152.1.125.2 0 200 254 ?
> > Rack1R5#
> >
> >
> >
> > R5 in AS 100
> >
> > R1 and R2 in AS 200
> > R5
> > router bgp 100
> > no synchronization
> > bgp router-id 150.1.5.5
> > bgp log-neighbor-changes
> > neighbor 150.1.4.4 remote-as 100
> > neighbor 150.1.4.4 update-source Loopback0
> > neighbor 152.1.125.1 remote-as 200
> > neighbor 152.1.125.2 remote-as 200
> > no auto-summary
> > !
> >
> > R1
> > router bgp 1000
> > no synchronization
> > bgp router-id 150.1.1.1
> > bgp log-neighbor-changes
> > bgp confederation identifier 200
> > bgp confederation peers 3000
> > neighbor 152.1.123.3 remote-as 3000
> > neighbor 152.1.125.5 remote-as 100
> > no auto-summary
> >
> > R2
> > router bgp 2000
> > no synchronization
> > bgp router-id 150.1.2.2
> > bgp log-neighbor-changes
> > bgp confederation identifier 200
> > bgp confederation peers 3000
> > neighbor 152.1.123.3 remote-as 3000
> > neighbor 152.1.125.5 remote-as 100
> > no auto-summary
> >
> >
> > Regards
> >
> >
> > ---------------------------------
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>
>
>
> --
> Kindest regards,
> hm
>
>
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>
-- Kindest regards, hm
This archive was generated by hypermail 2.1.4 : Sat Sep 01 2007 - 11:32:10 ART