From: Peng Zheng (zpnist@yahoo.com)
Date: Mon Apr 07 2003 - 16:52:07 GMT-3
Thanks. Yesterday, it preferred 192.168.1.249 even
after reloaded.
I just tried today, it preferred 192.168.1.241. I
don't know why.
--- Jonathan V Hays <jhays@jtan.com> wrote:
> Please verify the router IDs of those neighbors.
> Note that the router ID
> may not be the same as the Next Hop IP address. For
> example, see below
> where the next hop is 10.1.1.2 but the neighbor's
> router ID is
> 172.16.3.1.
>
> r2501a#show ip bgp neighbors
> BGP neighbor is 10.1.1.2, remote AS 2, external
> link
> BGP version 4, remote router ID 172.16.3.1
> BGP state = Established, up for 00:19:33
> [output omitted]
>
>
> > -----Original Message-----
> > From: Peng Zheng [mailto:zpnist@yahoo.com]
> > Sent: Monday, April 07, 2003 2:55 AM
> > To: Jonathan V Hays; ccielab@groupstudy.com
> > Subject: RE: Lowest BGP router ID prefered ?
> >
> >
> > But I implemented the same topology as that.
> > Sugarbush has three IP: 192.168.1.253 (to Stowe),
> > 192.168.1.238 (to Diamond) and 192.168.1.249 (to
> > Burke), so BGP ID is 192.168.1.253.
> >
> > And Diamond has three IPs too: 192.168.1.245 (to
> > Mammoth), 192.168.1.237 (to Sugarbush) and
> > 192.168.1.241 to Burke), so its BGP ID is
> > 192.168.1.245.
> >
> > And I got the same route table on burke( preferred
> > Sugarbush).
> >
> >
> > --- Jonathan V Hays <jhays@jtan.com> wrote:
> > > You are referring to BGP Best Path Selection:
> > >
> > >
> >
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios12
> > 1/121cgcr/
> > > ip_c/ipcprt2/1cdbgp.htm#1000898
> > >
> > > "12. If multipath is not enabled, prefer the
> route
> > > with the lowest IP
> > > address value for the BGP router ID.
> > > The router ID is usually the highest IP address
> on
> > > the router or the
> > > loopback (virtual) address, but might be
> implementation-specific. "
> > >
> > > I think you are mistaken on the IP addresses you
> > > gave since I don't see
> > > either 192.168.1.253 or 192.168.1.245 on page
> 191 of
> > > that book. Perhaps
> > > I have a different printing than you do. Anyway,
> I
> > > assume you are
> > > referring to Example 2-53 "Burke's BGP Table
> > > Contains Only the Aggregate
> > > Route" which shows 192.168.1.249 as having the
> best
> > > path instead of
> > > 192.168.1.241 (the lower IP address).
> > >
> > > Although the BGP router chosen as the Next Hop
> for
> > > this network happens
> > > to have the higher IP address value, you do not
> have
> > > enough information
> > > to say that it was the IP address value used by
> BGP
> > > to make that
> > > decision. There are eleven (11) previous steps
> in
> > > the BGP Best Path
> > > Selection hierarchy, any one of which takes
> > > precedence over this IP
> > > address criteria. The IP address criteria won't
> be
> > > used unless all of
> > > the other criteria are bypassed or are equal for
> > > both routers.
> > >
> > > Hope that helps.
> > >
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com
> > > [mailto:nobody@groupstudy.com] On
> > > > Behalf Of Peng Zheng
> > > > Sent: Sunday, April 06, 2003 10:21 PM
> > > > To: ccielab@groupstudy.com
> > > > Subject: Lowest BGP router ID prefered ?
> > > >
> > > >
> > > > Hi,
> > > >
> > > > It is said the route with lowest BGP router ID
> is
> > > > preferred. But I found the route with
> highest
> > > BGP
> > > > router ID os preferred.
> > > >
> > > > In Route TCP/IP V2, page 191, on Burke, the
> route
> > > with
> > > > BGP ID 192.168.1.253 is preferred to the route
> > > with
> > > > BGP ID 192.168.1.245.
> > > >
> > > > What's the reason?
> > > >
> > > > Thanks for help.
> > > >
> > > >
> > > >
> > > >
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>
This archive was generated by hypermail 2.1.4 : Thu May 01 2003 - 13:35:48 GMT-3