GRE Tunnel Maximum Bandwidth

[masoodst123]

Hi,

I Have a Cisco Router and a 6506 Switche which are interconnected through GRE and EIGRP, using only 2M CAT6 cable, but when i do IPERF bandwidth test between two computers one is connected to 6509 and one is connected to my router, the bandwidth test shows only 8Mbps throughput, is there any way to increase the amount of bandwidth between two computers.

Regards

[paul driver]

Hello
The reason why tunnel interfaces have such a low BW is to make that tunnel less preferred to routing protocols.

When you have tunnel interface it very possible to initiate recursive routing ( that is the path to the tunnel destination is via the tunnel itself) and this is easily done because a tunnel - tunnel connection is seen as only 1 hop count away from each other but the underlying physical path could be multiple hops away so to the routing protocols the tunnel path is deemed a better path, that why is the interface Bw is very low it will have a much higher interface cost and can assist in making the tunnel a less preferred option in routing.

So if you increase the tunnels interface BW you need to make sure this change doesn't adversely effect your overall routing

[masoodst123]

Thank you paul, so what is the best practice, how to use tunnel interfaces while utilizing the optimum througput available on physical link?

[paul driver]

Hello

You can set the tunnel BW to the same of its related physical interface Bw but just beware of what could occur after the such change as I stated previously.

[masoodst123]

Paul, i have already changed the bandwidth value to 100mbps, but still when i do iperf bandwidth test , it shows only 8mbps. 

[paul driver]

Hello

Changing any interface BW doesn't change the actual interface BW as i stated previously is only changes the routing cost of that interface.

[masoodst123]

Sir, i need a solution, so i could reach 100mbps throughput on the link.

[paul driver]

Hello

---

@masoodst123 wrote:

Sir, i need a solution, so i could reach 100mbps throughput on the link.

---

Do you have other options following the BW command under the tunnel interface?
int tun xx
bandwidth inherit xxxx
bandwidth receive xxxx


What ios feature set are you using?.

[masoodst123]

thanks, by changing the MTU size, the throughput size increased.

[Joseph W. Doherty]

What model router?

With GRE tunnels, you might be fragmenting maximum size packets. For TCP, this can be mitigated by using the TCP adjust-mss interface, (Reduce MSS by 24 bytes.)