6500 GRE performance

[Jon Marshall]

Using a 6500 with sup720-3BXL so GRE is supported in hardware with this supervisor but does anyone know if there is a limit to the amount of bandwidth you can get per tunnel. 

Looking to get up to a maximum of 1Gbps traffic if possible so interested to hear if anyone has done this. 

Jon

[rasmus.elmholt]

Hi,

I would expect you to get the 400Mpps times your MTU size as found here:
https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/product_data_sheet09186a0080159856.html

But let us know how it goes if you do a test:-)

Br,

[Jon Marshall]

Cheers for that. 

I seem to remember somewhere that even though GRE is done in hardware you cannot get there are limitations in terms of throughput but can't find the reference now. 

I will indeed update this thread if/when I get to test it :) 

Jon

[Joseph W. Doherty]

With IPv4 (and not "overloading" the source interface), I've run GRE across 10g interfaces. I recall (?) I was able to obtain close to gig (NB: further downstream, interfaces were gig).

However, if you want to do IPv6, you'll crush the CPU. (Believe IPv6, GRE wire-speed, needs a sup2T or sup6T.)

[Jon Marshall · Accepted solution]

Joe 

Thanks for that, good to hear you have actually got close to that figure using GRE. 

Just to clarify , talking about IPv4 only at the moment, if you had run it across a 1Gbps interface (rather than 10Gbps) would you still have expected close to 1Gbps ie. you are suggesting the 1Gbps connection further downstream is what actually limited it to 1Gbps ? 

I ask as at the moment I do not have any 10Gbps interfaces to use :) 

Jon

[Joseph W. Doherty · Accepted solution]

Jon, yes, for IPv4, I expect the sup720 will support wire-speed. I mentioned the 10g interfaces and downstream device gig interfaces, because the latter limited the tunnel's effective bandwidth to gig, which I saw it hit from time to time across the 10g interface.

I also mentioned that an IPv6 GRE tunnel, with any volume of traffic, crushes the sup720 CPU. It appears such does not have ASIC support. I recall I had contacted TAC and found Cisco didn't have plans to support IPv6 GRE, in hardware, on the sup720. (To clarify, IPv6 works across a sup720 GRE tunnel, but it caused my CPU to hit 100% pretty quickly. [Actually, as my wont, I got a bit too fancy, I defined an IPv6 GRE tunnel to also support IPv4 across it.])

[Jon Marshall]

Joe 

Cheers again, much appreciated. 

Will only be IPv4 at the moment so at least I know it is an option if we need it. 

Glad to see you can finally be a VIP, presumably because you have sort of retired (I seem to remember you saying something along those lines ?) 

Jon

[Jon Marshall]

I have absolutely no idea how my response became an accepted solution.

Will post in VIP forum. 

Jon