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New Member

Combining / bundling a Multilink and Giga 0/1 WAN interface?

Not sure what the term is that I'm looking for here, but is it possible to take and combine 2 ISP's into one "connection" each ISP we have different block of IP's assigned and connection types.

*What I'm trying to acomplish, I'll try and give as much detail now as possible"

We currently have an old 1721 Router setup with 2 t-1's that are multilinked together and a half a class C worth of public IP's on it =)

We also are in the process of upgrading to MPLS (from a service provider) and have some adtran router that we connect to the LAN port of to access this network/internet.

Our internal network is

We purchased a new 2921 ISR G2 and I've set this up to connect to the MPLS network over the giga 0/1 port which is connected to their router.  I have 2 extra T-1 WIC's and wanted to know if there is a way to add these to the ISR and then move the other ISP's T-1's into this router and have both WAN links work together and still only have one LAN gateway (  Basically making my life a little easier while we go through some DNS changes and test the MPLS side.

I read about NAT'ing public IP's to other Public IP's to help during transition times, but not sure this would be the easist way or work?

Or could we just take and setup both WAN links and route out ISP A and when connections are made to route ISP B's IP block, will they work ir try to route back out ISP B?

Or is this something that should be KISS and just add 2 static routes for ISP A and ISP B

ISP A (Public Block A)  >>>>>



                                                       >  RTR-2921 (




ISP B  (New Public Block)>>>

Hall of Fame Super Gold

Re: Combining / bundling a Multilink and Giga 0/1 WAN interface?

Hi, my recommendation would be you engage a networking professional to take responsibility and guide during the transition.

This kind of configurations is not appropriate for end-users, beside bundling ethernet and serial circuits is not possible.

New Member

Re: Load Balancing 2 ISP's on Multilink and Giga 0/1 WAN interfa

The term I was looking for was Load Balancing the 2 lines on the one router this way both IP spaces would still be active and allow for us to make the transition from 1 ISP to the other ISP and going from a hub and spoke to mesh topology.

I'm not to concerened about optimizing bandwidth or making this configuration perfect since it will only be temp. and currently the users are only getting 2 - T1's total.

Would enabling both ISP links on the router and creating 2 equal static routes to each isp do what we need?  Provided our NAT translations are setup correctly.  Or would this cause problems if has a mapping to 2 different public IP's on different links?

Can we have each ISP's public IP's translate to the same internal servers and ports at the same time or would this cause problems?

I went through the documents on OER and GLBP which seem like great options, but I'm assuming there is an easier (maybe not best practices) way to do this, since it's only going to be temp while work on the transition.

Thanks for any assistance.  If you need more detail or a better explanation let me know

Hall of Fame Super Gold

Re: Load Balancing 2 ISP's on Multilink and Giga 0/1 WAN interfa