GRE Tunnels

[james.king14]

Just a quick question about GRE tunnels and IPSEC Tunnels!  Using a GRE tunnel what is the minimum bandwidth?  I ask the same about IPSEC?  

I am using Wireless  and have AP's connected via GRE tunnels to Controller.  Was wondering what is approximate bandwidth used during connection (idle).  Lets say I have a 50 mpbs connection between two site how much bandwidth would the wireless utilize for GRE or IPSEC tunnel..

[Karsten Iwen]

There is nothing like GRE- or IPsec-Bandwidth. You only have some additional overhead based on the tunnel-headers and trailers. For GRE it could be something small like 24 Bytes, for IPsec you have something between 60 to 100 bytes of overhead.

Cisco has a nice tool to calculate the IPsec-overhead:

https://cway.cisco.com/tools/ipsec-overhead-calc/ipsec-overhead-calc.html

[georgehewittuk1 · Accepted solution]

Adding to this typically with GRE tunnel configuration may want to check the tunnel interface bandwidth end to end and the interface stats if seeing issues for output queue drops etc. By default I believe it's only 1mbps so is typically adjusted when designed/installed.

If you are trying to identify the 'bandwidth' you are actually using netflow could be useful to identify traffic trends.

[james.king14]

Thank you all for verifying my assumptions about the bandwidth usage of an GRE/IPSEC tunnel.