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Routing issue with multiple wan

Hey All,

I configured Cisco  1941 Router with two WAN.

1. ISP_1 i configured with Dynamic routing protocol (BGP), and ISP_2 (VSAT) is VSAT IDU.

2. For ISP_2 we configured static router with 230 metric.

Now the problem i having, when sent packet to my remote network then it is going through ISP_1 but return packets are comming through ISP_2.

I cant understand what to do....please suggest..


Routing issue with multiple wan

Can you diagram the setup?


Community Member

Re: Routing issue with multiple wan

Hey Devils,

this is the topology that im using.

Re: Routing issue with multiple wan

It sounds like what is happening, is that, outbound, it's obviously taking the correct link. When the return traffic comes back, other BGP routers, are choosing the path through the other ISP. This can happen because of a veriety of different reasons.

Are you advertsing out any networks via BGP, or is this extra link, simply for redundancy. I'm assuming you're advertising different networks out.

If the above is true, then you will need to tell Internet BGP routers, that you have attributes that will make the second link undesirable,  so that return traffic goes through ISP1.

The best way to accomplish this IMO, is my pre-pending your AS. So if your local AS is 100, other routers will see just [100], when being advertised out each network. You can pre-pend it by [100. 100. 100] through your second ISP, when advertising your networks, thereby making it less desirable, and return traffic will come through ISP1.

I'll take a look at the wireshark file, one I get to work, while drinking coffee unless someone beats me too it.

Hope this helped some

Community Member

Re: Routing issue with multiple wan

Hey john,

Im using second link for redundancy. As for that link configured only static route with 230 metric.

Re: Routing issue with multiple wan

When you see the data coming back, on the redundant link, is this from the laptop user?


Re: Routing issue with multiple wan

send us a traceroute mate, for the rest, Are you saying you have no BGP between your 2911 that connects you with CE_VSAT_IDU?     In which case you will not be able to influence the upstream path, using AS path prepending.

In which case, you will probably have to liaise with your provider and re-iterate your requirements.

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Community Member

Re: Routing issue with multiple wan

Hey Dennis,

CE_VSAT_IDU is managed  by ISP, they only provide me IP address for my use. Now i have two way to use it First one is i connect that link in switch and give each client(PC) manual IP address in rage of device(CE_VSAT_IDU) that is very  hectic, Second one is terminate link in router and configure STATIC ROUTE  with METRIC value.

I choose the second way and configuration that i done on router are correct. As we told our ISP after configuring CE_VSAT_IDU we are facing such problem that whenever user send data out to our network then it goes from primary path(MPLS) but when user receive data it comes from secondary ISP (CE_VSAT_IDU). After troubleshoot by ISP the problem get resolved. Now both path working fine.

ISP1(MPLS_VPN network) Service provider BSNL

ISP2(VSAT)Service provider BSNL

My worry is i want to know what was the issue is this. Because ISP don't share this issue with us.

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