Aastra 480i Administrator's Manual page 428

IP Phone Administrator Guide
Sample Configuration Files
#sip nortel nat timer: 60
# Option 2:
#
# If you are using a session border controller, you should set the
# outbound proxy to the session border controller address
#sip outbound proxy: sbc.aastra.com
#sip outbound proxy port: 0
# Option 3:
#
# If you know the public IP address of your NAT device and and have
# opened up a port for the SIP messages then you can statically
# assign this information.
#sip nat ip: 67.123.122.90
#sip nat port: 5890
# Additional Network Settings
#============================
#sip rtp port: 3000
#------------------------------------------------------------------
# Configuration Server Settings
# =============================
D-16
DFW Phone 972-992-4600
# seconds between keep alive messages
# a value of 0 enables SRV
# lookups for the address of
# the proxy.
# Eg. RTP packets are sent to port 3000.
41-001129-00 Rev 09, Release 1.4.1