WAN Link instability when configured for DHCP



  • Hello -
    Sharing my experience with pfSense 2.0.1 on AMD platform in the hopes that it save someone else's sanity. Don't know why it does what it does.

    Installed it to hard drive with 3 10/100 Ethernet NICs (WAN, LAN, OPT1 for DMZ).

    LAN has static IP and is set for auto negotiation (vx0)
    OPT1 has static IP and is set for auto negotiation (fxp1)
    WAN is set for DHCP and is set for auto negotiation (fxp0)

    Noticed poor throughput to the WAN and after investigating (looking at the link light on the card) saw that the link appeared to be toggling UP/DOWN/UP/DOWN… about every 30-40 sec.

    syslog showed nothing but dmesg showed "fxp0 Link UP" followed by "fxp0 Link Down".  This repeated forever.  While this was going on, the processor showed 100% and the UI was very sluggish (probably due to some process restarting).

    Swapped out Ethernet cards, no change. Swapped out hard drive, no change. Swapped to different Ethernet card (dc0), no change.

    Disconnected the WAN link. Everything stabilized, but no WAN now. machine became responsive again but now we have "Link Down"

    Swapped out OS from pfSense to m0n0wall (related firewall with apparently the same FreeBSD underlying OS ?kernel?).  Reconnected the WAN interface configured for DHCP.  Back to the same behavior.

    Swapped out OS from pfSense to TheWall (this uses PicoBSD).  Reconnected the WAN interface configured for DHCP.  System is stable and performance is great. Tells me it's not a hardware issue.

    Went back to pfSense and reconfigured for no auto negotiation on the WAN link. Back to bad Link up/down/up/down... behavior.

    Set the WAN link for Static IP with auto negotiation and system stabilized.

    Perhaps someone knows why it's doing what it's doing.  I'm fine with the config as it is as I don't need DHCP on the WAN side.

    Regards



  • @l2i28v5i:

    I'm fine with the config as it is as I don't need DHCP on the WAN side.

    Then why did you configure the WAN interface to ask a DHCP server for configuration information?

    @l2i28v5i:

    Perhaps someone knows why it's doing what it's doing.

    My GUESS is that dhclient doesn't get an answer to its DHCP request in "reasonable" time and resets the interface (link down/link up). There might be evidence in the system (see Status -> System Logs) to support this - look for reports from dhclient.


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