Cisco Support Community
Community Member

Bypass ISP through tunnel consisting of 3550s with EMI: FEASIBLE?

Dear fellows,

i have to solve a situation described as follows:

(OUR_POP_1 and OUR_POP_2 belong to us)

Thge current topology is as follows:


ISP_1 and ISP_2 have a peering point in london.

Normally, traffic between OUR_POP_1 and ISP_2 should be routed through ISP_1

and ISP_2.

However, i want to bypass this route and i want to forward this kind

of traffic only (ie traffic from OUR_POP_1 towards ISP_2 and vice-versa and

not internet

traffic in general) *not* through this route, *but* through a tunnel that

has its two

ends in OUR_POP_1 and OUR_POP_2.

Thus, traffic from OUR_POP_1 towards ISP_2 will be routed throughout the

ISP_1 backbone

and then it will be driven to OUR_POP_2, where we already have a peering

with ISP_2.

The questions are:

1) The border routers in OUR_POP_1 and OUR_POP_2 are cisco 3550 with EMI. Is

that feasible?

Can i create two GRE tunnels on both routers nad should this be enough? Is

it supported

by the 3550 and EMI IOS?

2) Any hints on the config?

Thanx in advance for your assistance guys,

BR from Greece,



Re: Bypass ISP through tunnel consisting of 3550s with EMI: FEAS

When I tried the interface tunnel 0 command followed by the tunnel mode command (which I set to 'gre ip'), the command was accepted on my 3550 (which is running the EMI). However, I remember reading some documentation that mentioned that GRE is currently not supported on the CAT3550 platform. I guess it would be safer to go by what the documentation has to say. Also, if you discover something new in this regard, please do let me know.

Community Member

Re: Bypass ISP through tunnel consisting of 3550s with EMI: FEAS

GRE tunnels are not supported on the Catalyst 3550-EMI. You can configure them and they will work. However, performance is considerably limited. I measured it with Smartbits. This is probably because it uses process switching rather than CEF. Cisco has not indicated if support for GRE will be forthcoming on the 3550-EMI.

CreatePlease to create content