MPLS Internet

Unanswered Question
Jan 20th, 2009

Our facility has 2 Internet connections and because of our current route config we can only utilize 1 of them. One connection is a 3660 router with 3 T1 serial interfaces configured in a Multilink. This Multilink interface connects to a MPLS network and then the Internet. The 3660 connects to a core switch.

The second internet connection is a single T1 serial connection attached to a smaller router. This router also connects to the core switch.

Our external DNS entries point to the single T1 connection so our systems can be access from the outside. We have default static route sending all traffic out this single T1. We tried removing the static route to send all traffic out the MPLS links. This worked except for the 'responses' our servers sent back to external requests also went out the MPLS links. Basically, and external request was coming in the single T1 then the response was sent out the MPLS link.

Would some form of ACL config fix this problem? We only have approximately 15 IP address's with external DNS entries.

I have this problem too.
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Giuseppe Larosa Wed, 01/21/2009 - 10:35

Hello Thomas,

if you have a block of 16 addresses from the provider that is connected to the single T1 this link will be used for inbound traffic and you cannot do anything about this.

if all links belong to the same provider cooperating with them you can fix this issue

Hope to help

Giuseppe

zebranutz80 Wed, 01/21/2009 - 10:44

All links belong to the same provider. What do you recommend I do with our provider to get things moving along.

Giuseppe Larosa Wed, 01/21/2009 - 13:08

Hello Thomas,

if all links belong to the same provider call their support people and ask them to change their routing so that also for them the primary path to those 16 ip addresses is via the 3T1 multilink.

Probably those ip addresses were linked to the service contract of the single T1 but they should be able to do the operation described above.

Hope to help

Giuseppe

zebranutz80 Thu, 01/22/2009 - 12:12

We had to put ACL's for every server in the router attached to the MPLS network. All default traffic was routed to this router then a PBR associated with the ACL's routed specific traffic back to the other router and T1.

Giuseppe Larosa Fri, 01/23/2009 - 10:04

Hello Thomas,

the suage of PBR is the fix you have implemented all in your side but other possible solutions are possible like the one I've suggested in previuos post to have the provider update its routing table to reflect the primary nature of the 3T1 multilink also for these 16 addresses

Hope to help

Giuseppe

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