GRE EGRESS METHOD

Unanswered Question
Oct 3rd, 2008

Hello,

A quick one from the experts. Is it advisable to use GRE egress method in the Data centre for the core WAE. I am avoiding it to cause service degradation. Any help?

I have this problem too.
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Zach Seils Fri, 10/03/2008 - 04:02

Oluwatodimu,

What type of platform are you performing interception on?

Thanks,

Zach

CSCO11117246 Fri, 10/03/2008 - 04:14

Hi Zach

I intend to intercept on a 3800 series edge router platform and on the remote site redirection is on a 2811 router.

Zach Seils Fri, 10/03/2008 - 15:04

Depending on the topology, you may or may not need GRE return. GRE return provides the following benefits:

- Negates the requirement for the WAE to reside on a dedicated subnet

- Statefully returns traffic back to the intercepting router.

If you'd like to send me a topology diagram, I can give you a definitive answer as to whether or not it's needed in your design.

Zach

Patrick Murphy Mon, 10/06/2008 - 05:46

Hi:

We are also looking to use GRE Return on our WAN routers at our datacenter. We have multiple different WAN routers that provided access to different provider network and need to ensure intercepted traffic returns to the same router. That being said, what are the disadvantages? Is there a performance hit to the routers or the WAE that would steer us away from GRE Return? For example, will a 3845 be able to handle a 45Mbps traffic load using GRE Return?

Thanks,

Patrick

Zach Seils Fri, 10/10/2008 - 08:06

Hi Patrick,

The performance impact is related to the increased throughput on the router. With GRE return, traffic will pass through the intercepting router twice in each direction. See attached spreadsheet for some performance testing results.

Regards,

Zach

Patrick Murphy Fri, 10/10/2008 - 08:22

Thank you for the speadsheet! It is exactly what I needed to see. This gives me the confidence that it will not max out the router.

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