Performance - GRE over IPSec or without GRE

[karim]

Looking at configuring a L2L VPN tunnel between two sites for voice traffic only.  Wondering if configuring GRE over IPSec VPN tunnel would add a load to the performace of the voice traffic vs configuring just a IPSec VPN tunnel? 

Wanted to configure a GRE for future where we may want to add more tunnels and enable EIGRP routing.       

Thanks any advice would be helpful.          

[Marcin Latosiewicz · Accepted solution]

Karim,

First of all GRE(oIPsec) is not the only option. You also have VTI, which does not add the GRE overhead and can run routing protocols on top.

In term of raw processing, yes GRE encapsulation is indeed another step on the way, however most of platform nowadays are able to handle this in CEF (or similar) or even in hardware (usually with certain limitations) like on 6500 etc.

Purely for voice there should be no impact on performance (depends also how you measure performance) since added overhead will not change much for actual audio, nor will added encapsultation add much of delay.

There are however other things to consider (like how to setup QoS not to introduce jitter).

M.

[karim]

Marcin,

Thanks for the information you provided.  I have mostly worked with GRE over IPSec however I read some of the information you provided in the past about VTI.  I am going to look at VTI to better understand and then hopefully have a chance to implement it.

Thanks again,

KM