Changing the MTU size in InterScan Web Security Virtual Appliance (IWSVA) 6.5 Service Pack 2 (SP2)

You can determine the current MTU size by running the following command:

# ifconfig

eth0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
        inet addr:192.168.xx.xx Bcast:192.168.xx.xx Mask:255.255.240.0
        UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
        RX packets:148761 errors:0 dropped:0 overruns:0 frame:0
        TX packets:157822 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000
        RX bytes:89324496 (85.1 MiB) TX bytes:67564376 (64.4 MiB)

1. To change the MTU size for one of the "eth0" interfaces, run the following command:

   # ifconfig eth0 mtu 1492

    

   "eth0" can be replaced by any other eth interface and the mtu size in this article is just an example.

   You can then verify the updated MTU size:

   # ifconfig eth0

   eth0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
           inet addr:192.168.xx.xx Bcast:192.168.xx.xx Mask:255.255.240.0
           UP BROADCAST RUNNING MULTICAST MTU:1492 Metric:1
           RX packets:150504 errors:0 dropped:0 overruns:0 frame:0
           TX packets:159845 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:89603113 (85.4 MiB) TX bytes:67839394 (64.6 MiB)

2. • To change the MTU size for the "br0" interface when IWSVA is set up in Transparent Bridge Mode, do the following:

     1. Log in as root on the IWSVA cli.

     2. Edit the iwsvanetfun.sh script.

        # vim /usr/iwss/iwsvanetfun.sh

     3. Find the following line:

        --------  add_param $iftargetcfg "IPV6_DEFAULTGW" "$IPV6_DEFAULTGW"  --------

     4. Add the following after the line above:

        --------  add_param $iftargetcfg "MTU" "1492"  --------

     5. Restart the IWSVA daemons:

         

        This will interrupt the network traffic for a few minutes so plan accordingly.

        /etc/iscan/rcIwss restart

     6. Run ifconfig to check the latest MTU settings.

   • If the MTU does not change in this way for br0, do the following:

     1. Edit the file /etc/sysconfig/network-scripts/ifcfg-br0
     2. Add "MTU=1492".
     3. Save the changes.

     4. Restart the network services:

        # service network restart

     5. Run ifconfig to check the latest MTU settings.