Redundant Routes, BGP with MPLS provider

Bill.Ingrum at Bill.Ingrum at
Fri Aug 31 16:21:16 UTC 2012

I think having a GRE tunnel for the internal routing protocol is
unnecessary.  Can you explain the reasoning behind this?  I understand
the technical issue whereby GRE will allow multicast for EIGRP, OSPF,
etc, but why not just redistribute into BGP?

I work on a lot of MPLS CE routers, and in general you can accomplish
anything you need by redistributing your internal routing protocol into
BGP, and adjusting LP, MED and AS Prepend as needed.



-----Original Message-----
From: Lee [mailto:ler762 at] 
Sent: Friday, August 31, 2012 11:15 AM
To: Tribble, Wesley
Cc: nanog at
Subject: Re: Redundant Routes, BGP with MPLS provider

On 8/30/12, Tribble, Wesley <WTribble at> wrote:
> Hello all,
> I am an Network Operator working in an Enterprise environment with 
> offices all over the country(mostly connected via MPLS).  We are 
> currently working towards building a Disaster Recovery Site that will 
> host some of our vendor routers and provide the capability to access 
> these vendors from both our primary and backup data center locations.

> The routes(as advertised by the vendor's routers) will be the same at 
> both locations.  I would like to advertise the routes from multiple 
> locations at the same time, rather than suppress the routes and
advertise conditionally.

At work, we have our internal routing protocol running on GRE over IPSec
tunnels & keep the BGP sessions with the MPLS provider limited to just
the MPLS network.  And have an ACL on the MPLS network
interface that allows only what's expected in...   some providers are
better than others at not having anything hit the 'deny any any log'


> What is the best method to Instruct the provider's network to prefer 
> the Primary Data Center routes over the DR site?  Keep in mind that I 
> am only peering with the provider over BGP and I have no visibility to

> the underlying MPLS architecture or configuration.  Although if you 
> have specific questions  about their architecture, I can work to get
> Discussing in house, we have gone over a few different options:
> -Advertise specific routes from primary site and summary routes from 
> the DR site.  Most specific will always be chosen.
> -Prepend the routes from the DR site so that they will have a longer 
> AS-path than the Primary location -Use Community Strings to influence 
> local preference.(Still working to find out if Provider will pass our 
> community strings)
> Just looking for some ideas and best practices.  Any thoughts or 
> insight would be much welcomed and appreciated.  This is my first 
> message on NANOG, so please be gentle.  I apologize in advance if I 
> have done something incorrectly.
> Wes
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