Hi All,

I've a 2910G (3.2.1), thats doing some strange things with my Cisco phones.

Short version: The Draytek seems to stop traffic from the Cisco phone, intermittantly, at random. Changing the source IP (at the phone) seems to fix.

Setup is this:

2910G provides WAN access to a remote office. The LAN there is used by both phones and PCs. Normally, the phones connect back to central office via SIP/RTP, via Public WAN Internet without any IPSEC tunnel.

However, this Draytek does have an IPSEC tunnel setup, which secures PC traffic back to Main office, and a second tunnel for securing VoIP to the same SIP server (future planning, not really in use yet). I can change whether phone traffic goes via IPSEC by changing the destination SIP IP in the phone, if I need to.

What I'm finding is that the phones will stop registering into the SIP server.

Through various tests, I've found that if I change the IP of the phone, then it starts working again. Or if I change the IP of the destination SIP server, then again it works, for a few days. Or if I reboot the 2910G.

other ciscos phones on the LAN will be working ok, at the same time.

Id say it was a NATing issue, but, if I change the dest SIP server, to use the IPSEC tunnel instead then theres no NATing, just routing.

Any ideas why the Draytek would do this ?

Theres probably a total of about 8 phones, and maybe 8-10 PCs in that remote office.