dual redundant network cards

Discussion in 'Hardware' started by chiguy, Oct 28, 2003.

  1. i am looking to use a dual dsl setup. share the load during normal times and automatically switch when one line goes down or burps. is their any special hardware or software that i need. i am running xp pro on two ibm xeon workstations. each machine has dual nic cards and i now have two dsl feeds.


    jack fahey
  2. Are you looking for redundancy to the networking hardware or to the connection itself, meaning have DSL and cable modem as a backup in case the DSL serivce is down?

    TM Trader
  3. simstim


    you could use a cisco router, but that's expensive. i have also heard of people doing this through linux but you're using xp.

    if you really want to have some kind of load balancing and have it failover to one if the other one goes down AUTOMATICALLY you'll need to be running some routing protocol (like RIP, i think windows runs this). otherwise you'l have to do it manually.
  4. Don't know how much real redundancy you'll get with two DSL lines.

    Since both lines would end up going over the same physcial wire bundle to the same central office. You'd only be protected in the event you lost one of the DSL modems or one of the central office interfaces. Any problem of greater magnitude (wire bundle severed, fault at the central office, failure of the upstream interface from the central office, etc.) would kill both DSL connections.

    You'd probably get better backup/redundancy by going with one DSL and one cable connection.

    You can't really use two machines each with dual NICs and connect both of them simultaneously directly to both lines though. With more than one computer, you should use a router.

    If you're insistent on automatic and transparent failover on a line failure, you'll need a dual line router like the Nexland Pro800. The cheaper approach would be to just manually swap the uplink line from the cable modem to a normal router with the uplink line from the DSL modem.

    Line and/or ISP channel failure is much more likely than a failure of a NIC or even a router.
  5. Hi,

    If I recall, this problem has been discussed here some months ago. I really don't have any direct experience with this but you can look at:


    Also Nexland used to have a similar unit. If I am not mistaken they have been taken over by Symantec in the meantime:


    It has been reported that a transparent switchover does not work 100% though. Does anybody have a favorable experience with this or similar units?


  6. i am worried about the connection rather than a hardware issue
  7. Then I'd suggest getting a DSL and a cable connection (each with their own modem of course). Install a DSL/cable NAT router like a Linksys (check for deals, I got mine for a $9 after rebates during a sale at Circuit City). Connect your PCs to the router and connect the uplink cable from the modem for the faster of the two lines (probably cable) to the DSL/cable port on the router. Configure the router to act as a DHCP server and configure your PCs to use DHCP.

    If you lose the cable, just switch the uplink cable to use the DSL modem and reconfig the router's connection parameters (FYI - cable modems don't usually require username/password login because they use the cable modem's hardware MAC address for authentication but DSL links usually require an actual uname/pswrd login - the router setup can be configured for either). The reconfig process would take about a minute or so.

    If you get a super cheap deal like the one I got my router, you might even want to install two routers and connect and configure one for the DSL and connect and configure the other for the cable. Then if you lose your primary link, just move the enet cables for your PCs from one router to the other. You could do this in seconds because you wouldn't even have to do a router reconfig.
  8. thaks a lot. i think i have a handle on this now

    jack fahey
  9. I recently purchased this router(@$189.00) to take advantage of the fact, that I have access to both Cable and DSL at my home. There are some great reviews of this little gem, http://www.tomshardware.com/network/20030918/, and http://www.lostcircuits.com/network/xincom_dpg402/ that can give a great insight to it's features, capabilities and performance.
    "Having two separate WAN connections theoretically offers twice the throughput of a single connection. However, there are a number of issues to bear in mind. First and foremost, it is not possible to use the dual WAN feature to speed up a single file download, each download has to go through its own WAN connection. Programs like flashgate or Download Accelerator can theoretically solve this issue and double the bandwidth if the files are downloaded from different servers. Unfortunately, flashgate still does not improve the situation since it will default back to a single WAN port. Download Accelerator, on the other hand, is capable of truly combining the bandwidth of both WAN ports and, thus, in situations where there are caps in place, double the bandwidth of a single connection as long as the servers can keep up with the requests". I'm trying to set-up Download Accelerator to do this today. I have tried the simple test of unplugging the cable modem, or the DSL connection during a download and there is a seamless transfer. This is the feature that interests me the most, as I resume actively trading this week. A cell phone set to speed dial my broker is also a must have. I know that many traders are successful using a 56k dial-up connection, and multiple broadband access is growing with bandwidth demand. My cable connection is$41/month for a 1650 Kbs download, and DSL is $37 for a 770 Kbs download speed. Upload is surprisingly slow on the cable(300 Kbs) compared to 575 on the DSL.