Another solution to this is since the BE is a Tenor (no other vendor supports BE) and it is an A800 behind the ADSL, you can use the Auto External IP feature. Basically, you set the A800 to register to the GK of the unit on the static IP and set the useipheader on the GK. There is a document on Quintums web site that explains this. It can be found at;
http://www.quintum.com/support/1G/sysdoc/webhelp/autoextip.htm
or
http://www.quintum.com/support/xplatform/network/Auto_External_IP.pdf