Softphone Traffic Routing

Posted on 2012-08-21
Last Modified: 2012-09-06

We have been asked to integrate around 25 softphones into our environment. Currently VOIP and Data is split into separate VLANs.

We are going to attach a second USB NIC to the PC's that need softphones. NIC 1 will be on the data VLAN and the USB NIC can be tagged to the VOIP VLAN.  

In testing this works to a degree. The USB NIC gets assigned to the VOIP VLAN and given the correct IP Etc.. I was planning on blocking all traffic apart from VOIP and allow access to the external TFTP server on our firewall on the VOIP VLAN.

When I do this I run into problems. Essentially... I need the USB NIC to only send VOIP traffic to the VOIP VLAN from the softphone, therefore not flooding our VOIP WAN connection with data traffic. NIC 1 should always handle any data traffic out of the data VLAN.

Is this possible to do? it seems that I need to do this at the source? NIC metrics and bindings seem to make no difference...

We are using a mixture of HP ProCurve 2520 POE  and 2910 switches.

Any ideas appreciated... Let me know if you need more info on the setup?

Cheers :)
Question by:jfreckeltom
    LVL 17

    Accepted Solution

    You could setup your VOIP NIC without a gateway, and add a static route towards the callmanager/sip server/other voice device to your routing table.

    But all in all, it seems like a bad idea to me: dual cables to all workstations, prone to errors...

    Why not just use the data vlan for voice? Those switches can do QoS based on layer3 DSCP, no real need for a separate vlan for voice. And the router/firewall can decide, based on the destionation address, which WAN to use: data or voice.
    A separate voice vlan for hard voip phones is a good thing, but not necessary for you, IMHO.

    LVL 29

    Assisted Solution

    Running a machine with two nics is a disaster in the making.  The problems you are seeing are just the tip of the iceburg.

    If your LAN is not overloaded just run the softphone over the normal Nic on the normal LAN segment.

    As long as there are less than 250 or so devices on the segment you'll be ok.  It is all "ones and zeros" and far as the cabling routing and switching are concerned,...the protocol is irrelevant.   QoS, as has been mentioned, is fine but it can also slow the normal LAN Traffic more than you might want.  Try without QoS first,...if the softphones start to "stutter" too much then add QoS.   But never make subnets bigger than /24bit segments,...keep them efficient,...keep them below 250 devices.

    Here's a sample list of the multihoming disasters.  Not all these apply to you, but the intention is to reveal that, a general rule, just plain "bad".

    157025 – Default Gateway Configuration for Multihomed Computers;en-us;157025&Product=win2000

    Default gateways

    Default Gateway Behavior for Windows TCP/IP

    159168 – Multiple Default Gateways Can Cause Connectivity Problems

    272294 – Active Directory Communication Fails on Multihomed Domain

    191611 – Symptoms of Multihomed Browsers;EN-US;191611

    Microsoft Windows XP – Multihoming Considerations

    Author Closing Comment

    Thanks for the comments. As you both suggested I decided to leave the dual NIC idea and run the softphones over the Data VLAN. No problems yet :)

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