bgp feed to customer

Jim Gonzalez jim at impactbusiness.com
Mon Jun 13 15:54:19 CDT 2011


-----Original Message-----
From: William Herrin [mailto:bill at herrin.us] 
Sent: Monday, June 13, 2011 3:34 PM
To: Richard Zheng
Cc: nanog at nanog.org
Subject: Re: bgp feed to customer

On Mon, Jun 13, 2011 at 1:25 PM, Richard Zheng <rzheng at gmail.com> wrote:
> This is probably a typical setup for border router not speaking BGP, 
> wonder how to handle it properly. Border router B is connected with 
> customer router C. Router C wants default-only/partial/full routes. 
> 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 
> customer routes, router A redistributes them from EBGP to OSPF.
>
> The issue is redistribution from EBGP to OSPF works half way. OSPF 
> database has the external routes, but forwarding address is set to 
> Router A. So the routing loop occurs between A and B.
>
> I wonder if it is a design issue or configuration issue?
>
>  ----------                  --------------                 
> ------------
> | BGP rtr A |  ============ | no-BGP rtr B |  ============ | Customer 
> | C |
>  ----------                  --------------                 
> ------------


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 at dirtside.com  bill at 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 

Now if the link Breaks between Router B and Customer C BGP will drop both
sessions. 

Thanks 
Jim Gonzalez





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