UC540 behind ASA using SIP

Answered Question
Mar 17th, 2012
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I want to set up a configuration like this:

Internet ----wan_ASA_lan-------wan_UC540_lan-----PCs and phones

But I want to use SIP.

If my UC540 wan port is going to be used to connect to the ASA lan port, how do I pass SIP traffic from the ASA to the UC540?

Thank you!

Correct Answer by rowseyba1 about 5 years 4 months ago

Yes sir.  Just 5060, unless your provider uses a different port. 

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Overall Rating: 5 (1 ratings)
rowseyba1 Mon, 03/19/2012 - 06:02
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This is fairly easy.  You just NAT your SIP traffic to from your ASA to the  IP address of your WAN port of your UC540.  Your SIP provider may need turn on far end NAT support for this configuration because you may get some 1 way audio if not.

I've also seen partners put the UC540 and the ASA side by side.  They would route the data out one of the LAN ports connected to the ASA and would put a public IP address on the WAN and route the voice out of that port.

Correct Answer
rowseyba1 Mon, 03/19/2012 - 09:14
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Yes sir.  Just 5060, unless your provider uses a different port. 

Simon O'Sullivan Thu, 03/22/2012 - 15:25
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If you are using a SIP trunk will you also need to NAT RTP traffic to the UC540?

clifford.gormley Mon, 03/19/2012 - 10:08
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yep, I was thinking of doing that, but my wan only has a /30.

Good to know that I was thinking along the same lines.

Thanks for your help.

Help Desk Tue, 03/20/2012 - 15:25
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Side by Side ASA and UC560 is very easy to do.  Simply plug your WAN port on your UC5xx to a port on the ASA and set the switchport to access mode on vlan2 (default wan vlan on asa).  Give your UC560 a public IP address in your scope and presto you are off and running.  No need to setup a NAT on the ASA as putting the switchport on the ASA in Access Mode on the Public VLAN will take care of this.

clifford.gormley Tue, 03/20/2012 - 15:31
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I never thought of that.  I was going to put a separate switch between the Internet and the ASA and UC, and get two public ips!

Thanks again.


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