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Best MTU value of RV042 with 2 WANs (cable + PPPoE)

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by gnuehcwc, Jul 29, 2006.

  1. gnuehcwc

    gnuehcwc Network Guru Member

    Hi

    What is the best MTU value of RV042 with 2 WANs (cable + PPPoE)

    I know my PPPoE MTU value is 1492 and I assumed my cable's MTU is 1500, so what is the best MTU value for both WANs?

    Thanks.
     
  2. jgutz20

    jgutz20 Network Guru Member

    well if the "maximum transmission unit" is 1492, that means the 1500 can be lowered to 1492 and still be under its maximum of 1500. So i'd say go with the 1492
     
  3. Toxic

    Toxic Administrator Staff Member

    if you enable telnet you could set the mtu manually I guess for each WAN.

    The following URL is used for telnetd temporarily.

    http://192.168.1.1/sysinfo123.htm?ConsoleSimulation=1

    telnet 192.168.1.1

    Username:admin
    Password:admin

    to make it permanent:

    rg_conf_set /nk/telnetd_enabled 1
    reconf 1
    flash_commit
    reboot

    then telnet back into the unit.

    once your in the cli, type

    shell

    for busybox.

    the do the following

    ifconfig ixp1 mtu 1492

    or

    ifconfig ipx2 mtu 1492

    typing ifconfig shows all ports but the WAN1 and WAN2 will eb something like so:

    ixp1 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:xx
    inet addr:81.xx.xx.xxx Bcast:xx.xx.xx.xx Mask:255.255.252.0
    UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:6224674 errors:0 dropped:0 overruns:0 frame:0
    TX packets:4514611 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:3107104814 (2963.1 Mb) TX bytes:1553207319 (1481.2 Mb)

    ixp2 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
    UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1492 Metric:1
    RX packets:570 errors:0 dropped:0 overruns:0 frame:0
    TX packets:395 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:82336 (80.4 kb) TX bytes:42748 (41.7 kb)


    WAN1 = ixp1
    WAN2 = ipx2
     
  4. gnuehcwc

    gnuehcwc Network Guru Member

    Thanks a lot. Toxic.

    But what is the MTU value setting in the Firewall section (set to auto) if I use the telnet method to change the MTU value. Do I need to change the MTU after each reset?

    Thanks.
     
  5. Toxic

    Toxic Administrator Staff Member

    Auto = 576 which is a total waste of having a setting like that for default.

    Set the MTU in the GUI to 1500, then telnet to busybox shell and adjust WANs independently.
     

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