TCP-MSS adjust does not work on MPC10E

[Louis Ho]

Does MPC10E support changing TCP-MSS on transit packets?



Today I need to set TCP-MSS to 1400,


My topological map


Server A > EX4300 A > MX960 A xe-4/0/0> > EX4300 B > server B

Serve A > EX4300 A > MX960 A et-5/0/0 > QFX-5110  > EX4300 C > server C


There are two line cards on my MX960 router, MPC 3D 16x 10GE and MPC10E 3D MRATE-10xQSFPP

I have configured tcp-mss on the two MPC interfaces, but the mss will only be adjusted if the traffic passes through xe-4/0/0,
but the traffic through et-5/0/0 does not work, the mss still keep at 1460.




show interfaces xe-4/0/0 | match mss
tcp-mss 1400;

tcpdump by serverB
https: Flags [S], seq 3239034622, win 29200, options [mss 1400,sackOK,TS


show interfaces et-5/0/0 | match mss
tcp-mss 1400;

tcpdump by serverC
Flags [S], seq 3355130726, win 29200, options [mss 1460,sackOK,TS val



Cheers