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New Member

ip tcp adjust-mss and ip mtu


i would like to know what the diffrence between the ip tcp adjust-mss command to ip mtu command.

when i need to config the first one command and when i need to config the second.


New Member

Re: ip tcp adjust-mss and ip mtu

hi amenash,

ip tcp adjust-mss command is used when you have pppoe or pppoa connection on your ethernet network where you add another header in it op pppoe or pppoA which is 4 byte. sometimes in wireless network you need to set this. if you don't set it your single packet size will be of 1500 and aditional header zise suppose 4 byte 1504 and it could be needed in the network to fragment in the network if there are multiple pppoe connection to reach to the network ppp server.

here is the detail.

The TCP MSS Adjustment feature enables the configuration of the maximum segment size (MSS) for transient packets that traverse a router, specifically TCP segments in the SYN bit set, when PPP over Ethernet (PPPoE) is being used in the network. PPPoE truncates the Ethernet maximum transmission unit (MTU) 1492, and if the effective MTU on the hosts (PCs) is not changed, the router in between the host and the server can terminate the TCP sessions. The ip tcp adjust-mss command specifies the MSS value on the intermediate router of the SYN packets to avoid truncation.

ip mtu is used to changed the MTU size of interface like gigabit interface could have upto 9000 byte

this document will definatly help you for the same.

please rate if it helps.