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VCS Starter Pack Expressway

Hello, Everyone.

We were donated some equipment to setup a SIP network and have been experiencing some issues.

For internal endpoints we have an EX90, C90, and MOVI clients.  We also have a single VCS Starter Pack Expressway (*without* the dual NIC option).

For our firewall imagine 3 interfaces: inside, outside, and DMZ.  The DMZ has public/Internet IP addresses.  There is no NATing between the inside and DMZ--it only NATs when traversing the outside interface (which of course is the interface connected to the Internet).

So let me just make up some addresses here for communications sake:

VCS Expressway: <-- public address

Internal Endpoint EX90:

Internal Endpoint MOVI:

Again, there is no NATing between the and network.

Everything works internally (registered through our VCS).  When we make an external call, say from the MOVI client, media gets to the external endpoint but we do not receive any media on the internal endpoint (not a single UDP packet).  We also noticed the media stream we send out is going directly to the external endpoint (or it's VCS), and not through our VCS Expressway.

Another interesting fact, when we put a small linksys router between the endpoints and our corporate network (endpoints on the LAN, corporate network on they WAN) everything works, and media from us paths through our VCS in the DMZ.  The only thing I can fathom is the VCS realizes there is now a NAT between the internal endpoint and himself, and alters the path.

I've looked through a lot of different documents (VCS Basic Config Guide, Expressway Starter Pack Deployment Guide, VCS IP Port Usage for Firewall Traversal Deployment Guide, etc.) and none of them that I've seen really cover our scenario.  Does anyone have any ideas on why the media isn't working properly?  I don't have access to the corporate firewall, but I'm told the UDP stream never gets back to us.

From what I've read in other discussions posted here, it seems like you only need the Dual NIC option if your VCS Expressway is being NATed to the Internet (which ours is not).  Is this correct?


-Matthew Pinkston

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