Redundant Routes, BGP with MPLS provider

Bill.Ingrum at Bill.Ingrum at
Fri Aug 31 16:33:45 UTC 2012

I work for an MPLS provider, so I guess I tend to trust them ;)


-----Original Message-----
From: Lee [mailto:ler762 at] 
Sent: Friday, August 31, 2012 11:28 AM
To: Ingrum, Bill
Cc: WTribble at; nanog at
Subject: Re: Redundant Routes, BGP with MPLS provider

On 8/31/12, Bill.Ingrum at <Bill.Ingrum at> wrote:
> I think having a GRE tunnel for the internal routing protocol is 
> unnecessary.

It might be, but we have a requirement for multicast over the wan so the
GRE tunnels had to be there.

>  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 see no reason to trust the provider that much.

> 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.

Sure.. but how do you *know* you're not getting anything added/removed
by the provider?


> Thanks,
> Bill
> -----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'
> line
> Regards,
> Lee
>> 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
> answers.
>> 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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