ip tcp adjust-mss on Catalyst 9500

[j.a.m.e.s]

Dear All,

I'm migrating an old c4948 to c9500-40x, but it appears the "ip tcp adjust-mss" option for a GRE tunnel is gone:

c9500-40x(config)#inter tun50
c9500-40x(config-if)#ip tcp adjust-mss 1360                             
                                   ^
% Invalid input detected at '^' marker.
c9500-40x(config-if)#ip tcp ?
  compression-connections  Maximum number of compressed connections
  header-compression       Enable TCP header compression

This is in Everest (v16.6). I read something on reddit about using Jumbos, but the problem here is that I'm using these switches as WAN agg and I can't yet do end to end Jumbos in this scenario. Does anyone know if Cisco plan to introduce adjust-mss in a later release? It is working on a 4500-x.

Regards

James.

[Georg Pauwen · Accepted solution]

Hello,

I think it is in Gibraltar 16.10...

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/16-10/configuration_guide/ip/b_1610_ip_9500_cg/configuring_tcp_mss_adjustment.html

[j.a.m.e.s]

Thank you Georg, that looks hopeful. We need to sort out our internal licensing before I can jump to that code, but it's good to know the feature has been added.