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Telnet / Dual MTU WAN Settings - RV042/RV082

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by Toxic, Aug 1, 2006.

  1. Toxic

    Toxic Administrator Staff Member

    OK guys I have added a tutorial to show how to enable Telnet and set MTU for Dual WANs. this maybe needed to allow for different WAN connections.

    ie

    WAN1 DSL connection needs MTU 1492

    WAN2 Cable connection needs MTU 1500.

    Also settngs for IPSec MTU on each WAN.

    check it out here:

    http://www.linksysinfo.org/forums/showthread.php?t=47539
     
  2. greg6000

    greg6000 LI Guru Member

    changing Dual WAN MTU settings for PPPoE/Cable via telnet

    Toxic,

    Would you know how to interpret this ifconfig output ( i deleted irrelevant output from the paste)? I have dual-wans, with PPPoE on WAN1 and Cable on WAN2.

    Taking note of your telnet MTU tutorial, I had a slight problem when busybox didn't recognize ixp1 when issuing the command "ifconfig ixp1 mtu 1492". ixp1 is my DSL modem ( according to the mac-address). Seeing the ppp0, I assume that i needed to apply the mtu to that (i.e. ifconfig ppp0 mtu 1492). Am I correct? ixp1 would remain the same (MTU=1500) and wouldn't matter since it is using PPPoE ? Since the ppp0 has no mac address, I am guessing that the ppp0 link "resides between" the ixp1 and the dsl modem when handling the MTU?



    / # ifconfig
    ixp0 Link encap:Ethernet HWaddr 00:xx:B6:81:66:EE
    inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
    UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:629 errors:0 dropped:0 overruns:0 frame:0
    TX packets:278 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:88667 (86.5 kb) TX bytes:34659 (33.8 kb)

    ixp1 Link encap:Ethernet HWaddr 00:xx:B3:81:49:DH
    UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:300 errors:0 dropped:0 overruns:0 frame:0
    TX packets:119 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:28983 (28.3 kb) TX bytes:8330 (8.1 kb)

    ixp2 Link encap:Ethernet HWaddr 00:xx:B1:80:99:F0
    inet addr:xx.xxx.xxx.xx Bcast:xx.xxx.xxx.xxx Mask:255.255.248.0
    UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:19765 errors:0 dropped:0 overruns:0 frame:0
    TX packets:268 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:1303429 (1.2 Mb) TX bytes:44660 (43.6 kb)

    ppp0 Link encap:point-Point Protocol
    inet addr:xx.xx.xxx.xxx P-t-P:xx.xx.xxx.xxx Mask:255.255.255.255
    UP POINTOPOINT NOTRAILERS RUNNING MULTICAST MTU:1492 Metric:1
    RX packets:88 errors:0 dropped:0 overruns:0 frame:0
    TX packets:85 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:3
    RX bytes:7690 (7.5 kb) TX bytes:4031 (3.9 kb)


    What's frustrating me is that even though the ppp0 is set to MTU=1492, various tweak tests keep telling me that the MTU is wrong and should be 1500, even though I know I am on PPPoE... Very confusing.

    Following up:

    I decided to re-test and set the all the MTU's to their default 1500, even the PPPoE linksys WAN link. The several mtu tests show that the 1500 works fine. Is there a chance that the DSL modem itself is doing the MTU 1492 to 1500 translation for me without the need for a Linksys MTU setting of 1492? That would make too much sense, but perhaps that is what is occurring ( DSL modem is a SBC 2Wire Portal).
     
  3. Toxic

    Toxic Administrator Staff Member

    You are infact correct. I dont have an ADSL modem to see what infterfaces are used by ADSL/PPPoE on the RV series.ixp1 would suggest this is used for "Obtain an IP Automatically"

    for ADSL you are recommended to use 1492 or lower. if it is already at 1492 then dont worry.
     

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