Cat 4500 GRE Tunnel performances

Unanswered Question
Feb 3rd, 2010

Hello, I have som performances issues with a GRE Tunnel on 4500 (12.2(37)SG with Supervisor V).

I think that GRE Tunnel is performed on SW, isn't ?

Does someone know the max throughput that we can get on that tunnel ?

I'm afraid that fragmentation can also decrease the performances, ho can I check the number of fragmented packet on that tunnel ?

I have this problem too.
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Hitesh Vinzoda Wed, 02/03/2010 - 07:10


Its true that GRE packets are process switched in 4500 series switches running with any codes  i.e Switched in software. I think it will give you performance between 5 to 15 Mbps at max. It may also lead to high CPU utilization during the specified data rates.


Hitesh Vinzoda

Giuseppe Larosa Wed, 02/03/2010 - 13:00

Hello Helenio,

use of GRE tunnels on a Cisco 4500 is not recommended it would lead to very high cpu usage with rather poor performances.

We also noticed that is not possible to move traffic in a VRF using a GRE tunnel in VRF.

What is your scenario?

Hope to help


helenio Wed, 02/03/2010 - 23:12

I'm using GRE tunnel cause I have to set up a EIGRP comunication over VPN-IPsec (2x Fortigate FWs). I did a test and I had 70% CPU with 40 Mbps traffic.

Do you see another way to establish a EIGRP Neighborship trhough a VPN IPsec Tunnel ?

For the VRF you mean that you can't assign a Tunnel to a VRF other that the Global one ?

helenio Thu, 02/04/2010 - 05:01

Where can I fing Tunnel performances based on RTR Model ?

helenio Thu, 02/04/2010 - 05:42

Thank's ... Tunnel GRE in Routers is done in Fast/CEF ? ...

Giuseppe Larosa Thu, 02/04/2010 - 09:15

Hello Helenio,

yes sw based routers have no dramatic performance penalties when handling GRE tunnels.

CEF for tunnel GRE should be supported in recent IOS releases

Hope to help



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