Remove IPtables entry Sophos XG

Hello Ben,

Thank you for contacting the Sophos Community.

You can use:

#ipset -L (To list out all output of IPset tables ipset -L <set name> : To list out detail about particular set)

#ipset -L | more (To show one page at the time)

About the MTU rule, what is the command you used to set the MTU?

Regards,

Why would you do this? 

I have two different MTU settings for the same thing, just wanted to clean it up.

Thanks,

iptables -t mangle -I POSTROUTING -d 172.19.0.0/16 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 900

Is the command looking at removing.

Hello Ben,

You can run 

# iptables -t mangle -D POSTROUTING -d 172.19.0.0/16 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 900

This will delete the entry(s) matching 172.19.0.0/16 located in the POSTROUTING, so if you have two entries for example:

Chain POSTROUTING (policy ACCEPT 4 packets, 240 bytes)
pkts bytes target prot opt in out source destination optimization
0 0 TCPMSS tcp -- * * 0.0.0.0/0 172.19.0.0/16 - tcp flags:0x06/0x02 TCPMSS set 900
0 0 TCPMSS tcp -- * * 0.0.0.0/0 172.19.0.0/16 - tcp flags:0x06/0x02 TCPMSS set 900

Then this will delete both of them, since they are duplicated, you can then just re-run the command.

# iptables -t mangle -I POSTROUTING -d 172.19.0.0/16 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 900

Also check if the entries are not part of the start script

# cat /scripts/system/clientpref/customization_application_startup.sh

Regards,

Thanks Emmanuel for the response, if I want to add it in the startup.sh, what is the best way to do that?

Thanks,

Ben

Hello Ben,

Enable editing of the startup script:

mount -no remount,rw /
Use vi to edit /scripts/system/clientpref/customization_application_startup.sh and add the lines. This should then look like:

#!/bin/sh
iptables -t mangle -D POSTROUTING -d 172.19.0.0/16 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 900
exit 0;

Save the changes and exit vi
Write protect the startup script again:
mount -no remount,ro /
Note:

In High Availability clusters the above will need to be applied on both nodes.

Regards,