VoIP Config

[backspace]

I have a client that is currently using a switch connected to his dsl
modem to "split" the connection between his data network and his VoIP
network. He has a WAN IP assigned to the VoIP phone system and
another WAN IP assigned to his IP firewall. He feels that this is
separating the VoIP traffic from the data traffic and therefore giving
VoIP traffic precedence.
I feel this is a worthless step and is in no way giving the VoIP
traffic a "path of less resistance" or precedence.
Is there in fact any merit to this config or is their truly no gain to
be had from this type of setup.

Thanks in advance for your help.

[Marco Mouta]

If he is able to setup TOS byte on IP header of his voice packets, and his ISP handles this byte correctly in his network... I would say that he will be giving QoS for voice packets when they leave their LAN.

But that depends on of what is the agreement between your costumer and your ISP. By the way his VoIP service provider is located in the core of the same ISP? otherwise QoS for TOS byte voice packets must be handled correctly along the path...

hard to guarantee i believe...

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[Gid Green]

Not sure how is povider is handling the VoIP traffic, however I have
seen similar setups.

The point of having the switch directly off the modem is to bypass the
need for nat or stun on the firewall. This can be done cheaper, no
need for a switch and to pay for extra IPs every month from the
provider.

Really what I have found to work best is to keep the VoIP traffic
behind the router/firewall, forward the correct ports to the sip
phones, and set up QOS to give the phones precedence over the rest of
the traffic.
-Gid