Using a DrayTek Vigor 2820 2830 or 2860 series gateway firewall router with SIP VoIP traffic

This really only applies if you are using a cloud based VoIP telephony provider with VoIP phones on your desks and you are using a DrayTek firewall. You will need to make a backup of all your settings and have your current firmware file to hand in case you need to roll back.

Disable SIP ALG

Using telnet, log in to the DrayTek’s interface (PuTTY is a good free client if you need one) with your admin username and password.

Type in the following commands:

sys sip_alg 0 (and press ENTER)
sys commit (and press ENTER)
sys reboot (and press ENTER)
– this will reboot your DrayTek

Reducing the NAT session time

On busy networks it can help significantly to reduce the default NAT session time on TCP traffic from 24 hours (!!) to 10 minutes.

Again, using telnet (as above) type in the following command:

portmaptime -l  (that is a lower-case L)
– this will show you the default of 86,400 seconds!
portmaptime -t 600
– this will change it to 600 seconds
sys commit
sys reboot
– this will reboot the DrayTek

This article can apply to

  • Vigor 2760
  • Vigor 2800
  • Vigor 2820
  • Vigor 2830
  • Vigor 2832
  • Vigor 2860
  • Vigor 2920
  • Vigor 2925
  • Vigor 2952
  • Vigor 2960