Ip TCP adjust-mss on VTI or GRE tunnel Interface

Lessons Discussion
1

Does the IP TCP adjust-mss command have any affect on a GRE or VTI tunnel interface?

2

Hi John,
The IP TCP Adjust-MSS command has no effect on a GRE tunnel. Source: http://www.cisco.com/c/en/us/td/docs/ios/12_2sb/12_2sba/feature/guide/sb_admss.pdf

Cisco’s best practices call for setting the adjust-mss to 1340 for IPSEC tunnels. Since, VTI is basically a simplified IPSEC tunnel, I would imagine the same recommendation applies. I was not able to find any documentation that stated VTI interfaces should be treated differently than an IPSEC tunnel interface.

–Andrew