Does MSS get increased with "ip tcp adjust-mss" command

[josephjthomas]

Hi,

I just needed more insite into the function of the ip tcp adjust-mss command which can be used to adjust the MSS value in the tcp syn packet which passes that interface.

But here is a question which I had. Consider that i have two sets of systems in my LAN one with an MTU value of 1300 ( MSS 1260 ) and with a MTU of 1500 ( MSS -1460 ). If I go ahead and put an ip tcp adjust-mss 1456 (for reducing the packet size from 1500 to 1496)  on the WAN . Does the command only lower the MSS for the set of systems which have 1460 or will it also increase the MSS in the tcp syn packets send by systems with MSS of 1260 ( which can potentially break some communication ).

JJT

[Joseph W. Doherty]

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Posting

It should not decrease mss below what's adjust-mss is configured for.  For example, if you use ip tcp adjust-mss 1456, it should only adjust if packet's mss is 1457 or larger.