[141894] in North American Network Operators' Group
RE: bgp feed to customer
daemon@ATHENA.MIT.EDU (Jim Gonzalez)
Mon Jun 13 16:56:10 2011
From: "Jim Gonzalez" <jim@impactbusiness.com>
To: "'Richard Zheng'" <rzheng@gmail.com>
In-Reply-To: <BANLkTi=MEfe2QkkFYETKmP79gNR2kEtLaw@mail.gmail.com>
Date: Mon, 13 Jun 2011 16:54:19 -0400
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
-----Original Message-----
From: William Herrin [mailto:bill@herrin.us]=20
Sent: Monday, June 13, 2011 3:34 PM
To: Richard Zheng
Cc: nanog@nanog.org
Subject: Re: bgp feed to customer
On Mon, Jun 13, 2011 at 1:25 PM, Richard Zheng <rzheng@gmail.com> wrote:
> This is probably a typical setup for border router not speaking BGP,=20
> wonder how to handle it properly. Border router B is connected with=20
> customer router C. Router C wants default-only/partial/full routes.=20
> Router B can't or is not willing to handle it. Router C has a multihop =
> EBGP session with a backbone router A. To get router B know the=20
> customer routes, router A redistributes them from EBGP to OSPF.
>
> The issue is redistribution from EBGP to OSPF works half way. OSPF=20
> database has the external routes, but forwarding address is set to=20
> Router A. So the routing loop occurs between A and B.
>
> I wonder if it is a design issue or configuration issue?
>
> =A0---------- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0-------------- =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0=20
> ------------
> | BGP rtr A | =A0=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D | no-BGP rtr B | =
=A0=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D | Customer=20
> | C |
> =A0---------- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0-------------- =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0=20
> ------------
Hi Richard,
Just a SWAG, but run IBGP on router B with just your internal routes
(including the customer route) instead of exporting into OSPF?
Regards,
Bill Herrin
--
William D. Herrin ................ herrin@dirtside.com=A0 bill@herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> =
Falls
Church, VA 22042-3004
Hi Richard,
Could you run a bgp session on Router B ? I had to do this once for
a customer because we had layer 3 switches on the edge with routing. I
configured 2 BGP sessions at the customer's router. The first session =
was
between Customer C and Router B. I only sent the default route to the
customer. The next session was ebgp multihop between Router A and =
Customer
C with full routing. I did allow the customer to announce the /30 to
Router B just so Router A could learn the return path or you could just
static route the /30 from Router A=20
Now if the link Breaks between Router B and Customer C BGP will drop =
both
sessions.=20
Thanks=20
Jim Gonzalez
