From: Jonathan V Hays (jhays@jtan.com)
Date: Mon Apr 07 2003 - 15:22:06 GMT-3
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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>
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This archive was generated by hypermail 2.1.4 : Thu May 01 2003 - 13:35:48 GMT-3