Static Route and BGP

[Joe Lee]

All-

My client has MPLS network via eBGP to communicate with all the sites. Here is the basic config on the router.

router eigrp 65210

neighbor 192.168.1.2 remote-as 13939

When they installed the internet on the local router, and added the static route on the router to hit the internet, they need to add the static route (2nd one) to communicate to the other sites.

ip route 0.0.0.0 0.0.0.0 75.75.75.1

ip route 192.168.0.0 255.255.0.0 192.168.1.2

ip route 172.20.0.0 255.255.0.0 192.168.1.2

They want to route all the traffic out thru the local intenet besides their private networks ( 192.168.0.0/16 and 172.20.0.0/16). Are there ways not to add last two static routes and communicate the other sites via eBGP? Please advise.

Regards,

Joe

[Harold Ritter]

Hi Joe,

The reason they had to add a route for 192.168.0.0/16 and 172.20.0.0/16 is probably that they only receive the default route from the MPLS cloud. When they add a static default route to the Internet on the local router, it overrides the one coming from the MPLS cloud and they lose connectivity to their own sites via the MPLS cloud. They need to start by investigating why it is that they only receive a default route via the MPLS cloud, which might be by design. If this is the case, the two additional static routes (192.168.0.0/16 and 172.20.0.0/16) are one of the few options to get it to work. They could also have the router that currently originates the default route in the MPLS cloud to also originate these two additional routes so they are received dynamically via eBGP on the local router.

Hope this helps

[Vivek Ganapathi]

Hi Joe,

Just to add to Harold's point. I believe they might have been accessing internet through a different site earlier (via MPLS). Hence there is a router which is originating a default route to the MPLS . Static route will override over the BGP learnt default route. Router originating the default prefix on MPLS also requires to originate (192.168.0.0/16 and 172.20.0.0/16). by doing that, you can remove the statically configured routes for those subnets.

You may decide to keep the BGP default prefix as is if you need (to achieve a redundant internet path) just incase if the local internet goes down, it prefers the BGP learnt default route & route via MPLS. But this requires some additional work - you need to run IP SLA to withdraw the static default route off the routing table upon certain condition (like failure of next-hop interface / icmp-echo failure to xyz IP address) etc.

[Joe Lee]

Hello Vivek,

Sorry for the late reply...just want to verify that I need to configure " default-originate" under BGP routing statement, that I can remove both static routes? Please verify.

Regards,

Joe

[Vivek Ganapathi · Accepted solution]

Hello Joe,

Default-originate is to originate a default route. But your requirement is to remove the static routes configured on the given router. You need to advertise 192.168.0.0/16 & 172.20.0.0/16 into the MPLS via BGP. This needs to be done on the router which has these network connected (not on the router whose configuration you have posted).

By doing this, you will start learning routes for 192.168/16 & 172.20/16 via BGP (MPLS). Then you can remove the static routes.

Please let me know if you have any confusions.

Regards

Vivek

[Joe Lee]

Thank you. got it now