UC320 and greyfield deployment

[canadianicon25]

I have a question about the model outlined in the greyfield scenario document.  My question pertains to the link between the WAN port on the 320 and a switchport on an existing router.

In the document the switchport on the router is placed into a newly created vlan, specifically VLAN4.  The address assigned to this VLAN is 192.168.2.253/30.  There is no IP address specified for the other side, but it could be infered that it would be 192.168.2.254/30 to maintain a common subnet.

My question is simply:  What is the point of this link and why is there a seeminly random VLAN created for it?  I am missing the point here and really need some clarification.

Any help from out there would be great!

[canadianicon25]

Following up to my own post:

In looking at the design guide I noticed that in figure 9, the voice and data vlan both goto the existing router (SA500 in the example).  The text below states that the voice vlan is not seen by the existing router.  Is there an error in the diagram?

[jeffsand]

Hi,

The general idea is that the data VLAN is being provided by your upstream router and the voice VLAN is provided by the UC320W.  Your UC320W LAN is connected and has an IP address on the data VLAN provided by the upstream router and your UC320W WAN is connected and has an IP address provided by the upstream router as well .  The reason you need another VLAN on the WAN is that you don't want your UC320W WAN and LAN to be on the same subnet to avoid loops (fundamental routing design criteria).  If you have Sip trunks, the voice packets to/from UC320W voice devices are routed over the WAN port to the upstream router and out the internet.

Jeff

[canadianicon25]

Insted of connecting to the existing router would it be possible to connect a (second) xDSL line to the WAN port and use that for just SIP trunks and firmware updates?