Failover Routing of Default Router BGP/MPLS

Answered Question
Apr 21st, 2009
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Here is my situation. I have an MPLS Network. We are running BGP for routing between sites. Right now there is one static route in the cloud to point all unknown traffic to our core site where the internet connection is located. We would like to setup a backup internet connection at one of our other sites and have the failover become automatic if the primary connection goes down.


FWIW, all sites except the core have static default routes pointing into the cloud. What are my options for this? Is it possible for the provider to setup two default routes in the cloud with different weights? Or do I need to remove the statics at the remote sites and redistribute from the primary and backup, but then how do I make sure the primary connection is weighted higher? Additionally, how do i properly track the status of the internet connections, IP SLAs?


Thanks in advance for any advice and assistance!

Correct Answer by Edison Ortiz about 8 years 2 months ago

I re-read your initial post and now I understand the network requirement.


My initial understanding was the remotes will have a secondary connection and you wanted those remotes to failover when the primary connection wasn't available.


The requirement calls for an additional site providing internet services but you want this site to function as secondary.


Well, same design stands - the secondary internet services site can advertise the 0.0.0.0/0 route via BGP and you can use the BGP attributes to make the secondary site less preferred. My suggestion will be to use AS-PREPEND on the secondary site on the 0.0.0.0/0 route during advertisement.


For instance,


ip prefix-list Quad0 permit 0.0.0.0/0


route-map Quad0 permit 10

match ip address prefix-list Quad0

set as-path prepend [AS#] [AS#] [AS#]


route-map Quad0 permit 20



route bgp as#

neighbor x.x.x.x route-map Quad0 out



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Edison.

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Edison Ortiz Tue, 04/21/2009 - 06:17
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How about advertising 0.0.0.0/0 from the Core site towards the remote sites via BGP/MPLS connection?


If remote sites stop getting the 0.0.0.0/0 from BGP, they can use the backup connection - provided the backup connection also receives a less preferred 0.0.0.0/0 route.


HTH,


__


Edison.

mloraditch Tue, 04/21/2009 - 06:27
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ediortiz,

The backup connection is at one site. So I can do what you say but how do i advertise the 0.0.0.0/0 route from the backup site so it is available but not in use while the primary is working?

Edison Ortiz Tue, 04/21/2009 - 06:33
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The 0.0.0.0/0 will be advertised from the Core site via BGP to all remotes.


The site holding the backup connection will receive this route with administrative distance of 20 eBGP.


You haven't mentioned what type of routing protocol the backup connection will have, but whatever you choose as the routing protocol, make sure the routes have a higher administrative distance so they can be less preferred.


__



Edison.

mloraditch Tue, 04/21/2009 - 07:00
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so can i have ip route 0.0.0.0 0.0.0.0 X.X.X.X in my core router and ip route 0.0.0.0 0.0.0.0 X.X.X.X at the backup site and redistribute them both into BGP setting the redistribute static metric on the primary site to 10 and at the backup site to 250?

I just setup a dummy route doing that and it looks like it did what i want

Correct Answer
Edison Ortiz Tue, 04/21/2009 - 07:07
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I re-read your initial post and now I understand the network requirement.


My initial understanding was the remotes will have a secondary connection and you wanted those remotes to failover when the primary connection wasn't available.


The requirement calls for an additional site providing internet services but you want this site to function as secondary.


Well, same design stands - the secondary internet services site can advertise the 0.0.0.0/0 route via BGP and you can use the BGP attributes to make the secondary site less preferred. My suggestion will be to use AS-PREPEND on the secondary site on the 0.0.0.0/0 route during advertisement.


For instance,


ip prefix-list Quad0 permit 0.0.0.0/0


route-map Quad0 permit 10

match ip address prefix-list Quad0

set as-path prepend [AS#] [AS#] [AS#]


route-map Quad0 permit 20



route bgp as#

neighbor x.x.x.x route-map Quad0 out



__


Edison.

mloraditch Tue, 04/21/2009 - 07:39
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edison,

thanks that works perfectly i tested with a static route for single ip and it did just what i wanted!

Your help is greatly appreciated!

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