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Contributor

Is there a recommeded MTU for voice/video traffic?

Hi All

Can anyone tell me if there is a recommended ip mtu for voice and video?

We seem to be having some issues with video over one of our tunnels and was wondering if increasing the mtu would make it any better?

cheers

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VIP Advocate

Re: Is there a recommeded MTU for voice/video traffic?

Hi,

Which type of tunnel? What is current MTU size? 

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution If this comment will make help you!
Contributor

Re: Is there a recommeded MTU for voice/video traffic?

GRE tunnel protected with IPSEC, current MTU is 1400

VIP Advocate

Re: Is there a recommeded MTU for voice/video traffic?

Hi,

I am not aware of any recommendation in your case but let we work on your case as:

If your ISP supported MTU is: 1500

 

MTU on GRE Tunnel: 1500 (ISP) - 58 (IPsec) - 24 (GRE) = 1418

Ethernet interface facing to ISP: MTU should be 1500

On our Tunnel MSS: 1418-40B (TCP Header)=1378

We also recommended configuring command on the GRE tunnel "tunnel path-MTU-discovery".

 

More details: https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html

 

 

 

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution If this comment will make help you!
VIP Advisor

Re: Is there a recommeded MTU for voice/video traffic?

Hello Carl

Incorrect mtu would be a problem but that looks okay so are you sure this  isn't due to traffic congestion on the line, are you implementing any quality of service?

 

Can you post details of your current topology is applicable?



kind regards
Paul

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VIP Mentor

Re: Is there a recommeded MTU for voice/video traffic?

Hello,

 

actually, Cisco recommends an MTU of 1400 (and a subsequent MSS of 1360), according to the document below:

 

--> The MTU value of 1400 is recommended because it covers the most common GRE + IPv4sec mode combinations. Also, there is no discernable downside to allowing for an extra 20 or 40 bytes overhead. It is easier to remember and set one value and this value covers almost all scenarios.

 

https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html#anc6

 

 

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