RV042 + X-Modem M3 (UK only)

Discussion in 'Cisco Small Business Routers and VPN Solutions' started by arr2036, Sep 2, 2006.

  1. arr2036

    arr2036 Network Guru Member

    It seems theres a loss of sync issue between the X-modem M3 and the rv042, when the modem loses sync, the router then stops routing any data to the wan port, all lan side stuff is fine, but anything attempt to access anything through the wan port fails , even the X-Modems config page.

    The simple way to fix the issue is to renew the wan port DHCP lease, then everything comes back up instantly... It's just a really annoying issue and I was wondering if anyone else was experiencing it.
  2. Toxic

    Toxic Administrator Staff Member

    what MTU are you using?
  3. pablito

    pablito Network Guru Member

    When you say loss of sync you don't mean the DSL sync (sync light on the modem), you mean that you loose your IP on the WAN port of the RV going to the LAN port of the modem?
    If that is the case perhaps you may need to enable "Keep Alive..." instead of the default "Connect on Demand.." This makes it act more like a regular PC connected to the modem. This also means you are doing double NAT since the modem is preconfigured with the DSL login and NAT, and the RV is also doing NAT. We can perhaps fix that too but it isn't critical to getting online.
    BTW, it would be important to know if you pay for connect time or if "always on" is ok.
  4. arr2036

    arr2036 Network Guru Member

    When the modem looses sync on the line itself (sync life goes off and starts flashing). The ip on the wan port never changes, recently brought a static ip to see if it would cure the problem but it didn't. Oh and when the modem loses sync the ip on the wan port stays the same.

    The X-Modem is very unusual in that it passes through the external ip to the RV via DHCP, so the rv thinks it's directly connected to the internet.

    MTU is set to 1458 on the router my pc and the modem.

    Modem is set to auto reconnect, which it does fine.

    And no, time is unlimited :)
  5. pablito

    pablito Network Guru Member

    Oh, that is different, and interesting. Have you tried it with a pc directly connected? A sync loss doesn't sound like an issue with the RV, it is further up the layers that only the modem has to deal with.

    Although likely not a problem, the MTU from the LAN side of the modem back can probably run at 1500 since it is Ethernet. The DSL WAN side will be more fussy with MTU.

    And just a tip, make sure all filters are in place on the analog devices. I like to run a twisted pair line from the demarcation point to the modem. Or at least replace the line from the wall to the modem. The flat phone line they give you isn't as good as a proper twisted pair line.
  6. arr2036

    arr2036 Network Guru Member

    Will do when I have it setup properly :) , using one of those fancy ADSL nation face plates, seems to have upped my snr by about 3db over the stock filter :D.

    I'm pretty damn sure it's nothing to do with MTU, if i set 1500 router side wouldn't the packets get fragmented at the modem ?

    With the pc directly connected it works fine, though for some reason the pc does always renew it's dhcp about a minute later, around the time the router stops routing traffic.

    Ethereal logs taken between the modem and the router with a hub, show that the router stops routing traffic completely from lan - > wan about a minute after the signal comes backup. The best way to fix it is by renewing the wan dhcp lease, after it's renewed the ip everything starts again fine, but of course this can't be done remotely.

    I'm thinking it might be a bug in the failover function, although I have got it set to DMZ mode and disabled internet connection detection.

    I've sent my ethereal logs and network setup to one of the more senior techs in india, and he promised to forward them on to the engineering people, so hopefully it will be fixed in the next firmware update.

    Just if anyone else is using this combination and it's working fine for them, please please let me know, because then I can safely say it's a hardware/flashing fault.
  7. arr2036

    arr2036 Network Guru Member

    Oh this is great, one of the techs in the phillapines told me today "this is a limitation of the rv042 and it's common on all routers that if the modem loses dsl syncronisation you have to resyncronise the router and modem"

    by syncronising he meant power cycling them both >_<

    *bangs head on desk*

    So I calmly explained to him that yes, that was admittedly a fix which is easy to perform locally, but when your 200 miles away and your VPN stops working because the routers managed to **** itself up the arse (didn't use quite those words), It's a little hard to power cycle the modem let alone the router. Especially when you can't access either of the web configs :|.
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