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7942 VPN phone not auto-detecting need to log in to VPN

We're trying to roll out some 7942 IP phones with the Anyconnect client built in.  My understanding is that when the phone boots up, it tries to determine if it's on a corporate network (ie. can reach it's callmanager(s)) and if not, presents the user with a VPN login prompt.

This is working at several users' homes, but other users' phones get stuck at a "registering" prompt.  On at least one of these phones, looking at the phone's embedded web pages, I see that the TFTP server IP address is set to the home router's IP address.  This makes me think that some home routers are providing a DHCP Option 150 (TFTP Server) populated with the home router's IP address.

Statically assigning an IP address on the phone has allowed the phones to detect that they need to prompt for a VPN login, but this procedure involves a lot of time supporting end users through unlocking settings on the phone and setting a static IP (and trying to ensure that the IP chosen is outside their home router's DHCP dynamic IP range)

Can anyone confirm if they know of any home routers that do indeed send DHCP Option 150 in this manner, and if so, is there something we can do with the IP phones before shipping them to remote users to increase the chances that the phone will work out of the box?

In case it helps, the firmware we're running on these CP-7942G's is



Adam Johnson

  • IP Telephony
Everyone's tags (4)

7942 VPN phone not auto-detecting need to log in to VPN


We advise our customers to hard-set the Alternate TFTP on the phones prior to shipping them out to users for this reason.  Much simpler than setting static IP address.


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