Multilinking GRE tunnels together.....

[gavink]

Hi all,

I'm trying create a virtual pipe by bonding together 2 GRE tunnels over 2 Leased Lines terminating on two different remote routers from one single location, then terminate the tunnel on another router on the net, and trying to bundle them together at each end, to make it appear as one virtual pipe to each end.

I probably haven't explained it very well, so I'll explain what I've done, and hopefully you might be able to tell me where I'm going wrong.

I've got a Cisco 1720 terminating 2 2Mbps Leased Lines to my net. Each one of the links has it's own IP range, and is running PPP. My provider can't bundle these together. I have another box sitting on a 100Mbps network link. My plan was to set-up 2 tunnels, 1 from each Leased Line, and terminate them both on the box on the 100Mbps network, and then route via that.

I've manged to set up the tunnels, and while in the tunnel interface, noticed that you could assign it to a multilink group. So, I did using the following:

interface Tunnel0

no ip address

multilink-group 1

tunnel source Serial 0

tunnel destination *remote address*

interface Tunnel1

no ip address

multilink-group 1

tunnel source Serial 1

tunnel destination *remote address*

interface Multilink1

ip unnumbered fast0

no cdp enable

ppp multilink

multilink-group 1

encapsulation ppp

And doing the same at the other end in reverse. When I do "show ppp multilink", I get:

Base-Band#sh ppp multilink

No active bundles

Multilink1 (inactive)

Member links: 2

Tunnel0 (inactive)

Tunnel1 (inactive)

I can not seem to be able to get the multilink interface up.

I can't seem find any documentation on Cisco's site that is helpful. If anyone has any ideas, or knows whether this can actually be done, I'd be most grateful.

Cheers,

Gav

[MickPhelps]

Is there a reason that you can't use equal cost routing (static or dynamic) to load balance over both tunnels rather than trying to bond them?

Mick.

[gavink]

I've got that working fine. It's more from a support point of view. I'm trying to present this a viable solution for other customers, and our support teams aren't that hot on routing. I'm also looking at it from a configuration point of, I think using a single pipe will be alot simpler to configure. Is it actually possible do you think?

[seilsz]

I suspect you're having problems because the tunnel interfaces do not use PPP encapsulation. Multilink bundles are designed for bonding multiple PPP encapsulated interfaces together.