FIREHOL-TCPMSS(5) - Linux man page online | File formats

Set the MSS of TCP SYN packets for routers.

Built 04 Nov 2017
firehol-tcpmss(5) 3.1.5 firehol-tcpmss(5)


firehol-tcpmss - set the MSS of TCP SYN packets for routers


tcpmss { mss | auto } [if-list]


The tcpmss helper command sets the MSS (Maximum Segment Size) of TCP SYN packets routed through the firewall. This can be used to overcome situations where Path MTU Discovery is not working and packet fragmentation is not possible. A numeric mss will set MSS of TCP connections to the value given. Using the word auto will set the MSS to the MTU of the outgoing interface minus 40 (clamp-mss-to-pmtu). If used within a router or interface definition the MSS will be applied to outgoing traf‐ fic on the outface(s) of the router or interface. If used before any router or interface definitions it will be applied to all traffic pass‐ ing through the firewall. If if-list is given, the MSS will be applied only to those in‐ terfaces.


tcpmss auto tcpmss 500 tcpmss 500 "eth1 eth2 eth3"


· firehol(1) - FireHOL program · firehol.conf(5) - FireHOL configuration · firehol-interface(5) - interface definition · firehol-router(5) - router definition · FireHOL Website ( · FireHOL Online PDF Manual ( · FireHOL Online Documentation ( · TCPMSS target in the iptables tutorial (‐ ables-tutorial.html#TCPMSSTARGET)


FireHOL Team.
FireHOL Reference Built 04 Nov 2017 firehol-tcpmss(5)
This manual Reference Other manuals
firehol-tcpmss(5) referred by firehol-conf(5) | firehol-router(5)
refer to firehol(1) | firehol-conf(5) | firehol-interface(5) | firehol-router(5)
Download raw manual
Index 3.1.5 (+194) FireHOL Reference (+109) № 5 (+2141)
Go top