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Cisco ASA Series Firewall ASDM Configuration Guide
Chapter 17 Configuring the Cisco Phone Proxy
Configuring the Phone Proxy
Note If NAT is configured for the TFTP server, the NAT configuration must be configured prior to specifying
the TFTP server while creating the Phone Proxy instance.
Step 4 In the TFTP Server IP Address field, specify the address of the TFTP server. Create the TFTP server
using the actual internal IP address.
Step 5 (Optional) In the Port field, specify the port the TFTP server is listening in on for the TFTP requests.
This should be configured if it is not the default TFTP port 69.
Step 6 In the Interface field, specify the interface on which the TFTP server resides. The TFTP server must
reside on the same interface as the Cisco Unified Call Manager (CUCM).
Step 7 Click OK to apply the settings.
Configuring Linksys Routers with UDP Port Forwarding for the Phone Proxy
When IP phones are behind a NAT-capable router, the router can be configured to forward the UDP ports
to the IP address of the IP phone. Specifically, configure the router for UDP port forwarding when an IP
phone is failing during TFTP requests and the failure is due to the router dropping incoming TFTP data
packets. Configure the router to enable UDP port forwarding on port 69 to the IP phone.
As an alternative of explicit UDP forwarding, some Cable/DSL routers require you to designate the IP
phone as a DMZ host. For Cable/DSL routers, this host is a special host that receives all incoming
connections from the public network.
When configuring the phone proxy, there is no functional difference between an IP phone that has UDP
ports explicitly forwarded or an IP phone designated as a DMZ host. The choice is entirely dependent
upon the capabilities and preference of the end user.
Configuring Your Router
Your firewall/router needs to be configured to forward a range of UDP ports to the IP phone. This will
allow the IP phone to receive audio when you make/receive calls.
Note Different Cable/DSL routers have different procedures for this configuration. Furthermore most
NAT-capable routers will only allow a given port range to be forwarded to a single IP address
The configuration of each brand/model of firewall/router is different, but the task is the same. For
specific instructions for your brand and model of router, please contact the manufacturer’s website.
Linksys Routers
Step 1 From your web browser, connect to the router administrative web page. For Linksys, this is typically
something like
http://192.168.1.1.
Step 2 Click Applications & Gaming or the Port Forwarding tab (whichever is present on your router).
Step 3 Locate the table containing the port forwarding data and add an entry containing the following values: