Re: EBGP Not changing Next Hop

Found the RFC - RFC 1771, go to the next hop section.

This is what happens at IXs - when you are on the same LAN segment as
hundreds of other ISPs. The NH attribute for prefixes originated by one of
the members will not be changed even if you didn't receive the routes from
them directly - because you are on the same LAN as them too!

Hope that explanation helps.

Cheers

Emmanuel

On 11 December 2010 15:02, Fabian Pucciarelli <fabiangp_at_gmail.com> wrote:

> That is correct, this is the normal behavior I see in vpls, try multihop
> loopback to loopback see what changes.
> On Dec 11, 2010 7:23 AM, "SD" <networker.ccie_at_gmail.com> wrote:
> > Hi,
> >
> > I have a below scenario can some 1 explain me why ebgp is not changing
> next
> > hop in the below sceario
> >
> >
> > R1, R2, R3 in the same Broadcast Segment
> >
> > R1 : 10.10.10.1 AS : 100
> > R2 : 10.10.10.2 AS : 200
> > R3 : 10.10.10.3 AS : 300
> >
> >
> >
> >
> > R1--------ebgp-------R2--------ebgp------R3
> >
> >
> > Routing update sent by R1 to R2 is sent to R3 via eBGP but R2 does not
> > change the next hop from 10.10.10.1 to 10.10.10.2
> >
> >
> >
> >
> >
> >
> >
> > R3 Debug output, although output shows route travelling through 2 AS but
> the
> > next hop is direct. Can some one pleaswe explain me why already tried
> > googling but no success...
> >
> > R3# OPEN has CAPABILITY code: 2, length 0
> > 00:09:57: BGP: 10.10.10.2 OPEN has ROUTE-REFRESH capability(new) for all
> > address-families
> > BGP: 10.10.10.2 rcvd OPEN w/ remote AS 200
> > 00:09:57: BGP: 10.10.10.2 went from OpenSent to OpenConfirm
> > 00:09:57: BGP: 10.10.10.2 went from OpenConfirm to Established
> > 00:09:57: %BGP-5-ADJCHANGE: neighbor 10.10.10.2 Up
> > 00:09:58: IP: s=10.10.10.2 (FastEthernet0/0), d=10.10.10.3, len 126, rcvd
> 0
> > 00:09:58: BGP(0): 10.10.10.2 rcvd UPDATE w/ attr: nexthop 10.10.10.1,
> origin
> > i, *path 200 100*
> > 00:09:58: BGP(0): 10.10.10.2 rcvd 1.1.1.1/32
> > 00:09:58: BGP(0): Revise route installing 1 of 1 route for *1.1.1.1/32->
> > 10.10.10.1* to main IP table
> > 00:09:58: IP: s=10.10.10.2 (FastEthernet0/0), d=10.10.10.3, len 40, rcvd
> 0
> > R3#
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Sat Dec 11 2010 - 15:06:42 ART