[c-nsp] GRE tunnel 8000kbit (8Mbit) limit issue

[Mack McBride]

I have seen this problem on various cisco switches (3550, 3560, 3750, 4948).
They don't support GRE in hardware.
The rest of the 49xx series and 45xx doesn't do it in hardware either
As far as I know.

Under certain circumstances software handling even happens on the 6500.
GRE tunnels can eat the cpu even if It is done partially in hardware.
Enabling certain features will cause it to be done partially or completely in software
on the 6500.

Frankly a software router is better for GRE termination.
The ASR1K series is great for it but it is technically still done in software.
It just has a huge number of cores to do the encapsulation.

Mack McBride | Network Architect | ViaWest, Inc.
O: 720.891.2502 | mack.mcbride at viawest.com | www.viawest.com | LinkedIn | Twitter | YouTube


-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Wednesday, July 15, 2015 3:24 PM
To: A.L.M.Buxey at lboro.ac.uk
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] GRE tunnel 8000kbit (8Mbit) limit issue

Hi,

On Wed, Jul 15, 2015 at 06:55:57PM +0000, A.L.M.Buxey at lboro.ac.uk wrote:
> (though more googling finds statement of no official support for GRE
> even on 3750-X or that it cannot terminate GRE... well, the commands are there and the tunnel works..

Classic IOS misfeature - "if the hardware cannot do it, just pretend everything is all right and try to do it in software".  At least a word of warning would have been nice...

(Sometimes it's handy to have a feature-in-software for management purposes, if you *know* there is not going to be much traffic over it, but the box need to tell you so)

gert


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