252 2 0 0 0 - A 2 - G B 2 3 - 0 0NAT Local Server ConfigurationA NAT Local Server entry is used when the local device shares its IP addresswith the WAN port of the IAD. Only the configured protocol and port will bevisible from the Internet. When the Local Server is configured, the followinginformation must be entered:• Translated IP address − local IP address, as seen from the LAN.• Protocol − TCP, UDP, AH, ESP, or both UDP and TCP.• Translated Port Number − port number on which the local server sees theservice (UDP and TCP only).• Standard Port Number − port number on which the Internet sees the service(UDP and TCP only).For current port number assignments, please see http://www.iana.org/assignments/port-numbers.Note that TCP port 1723 is used to select Point-to-Point Tunneling Protocol(PPTP) and TCP port 1720 is used to select ViaVideo. When using ViaVideounits through NAT, the following limitations apply.• Only one Via Video inside of NAT may accept calls.• All ViaVideo units in the network must be configured to use fixed ports 3230− 3235.• All ViaVideo units inside of NAT must be configured to use NAT and musthave the IAD’s WAN address configured.If Internet access of a local Telnet server at TCP port 23 is desired, it will benecessary to reconfigure the Telnet server port of the IAD. Refer to“Configure Port IP Address” on page 4-82 for further information.NAT Alias ConfigurationA NAT Alias entry is used when the local device is assigned a unique IPaddress from the WAN port of the IAD. The local device will be totallyaccessible from the Internet. When the Alias entry is configured, thefollowing information must be entered:• Local IP Address − the local IP address as seen from the LAN.• Internet IP Address − the IP address of the device as seen from the Internet.When configuring a NAT Alias entry, the alias’s Internet IP address must alsobe configured on the WAN port. This must be configured with an IP mask of255.255.255.255 if the alias’s Internet IP address is on the same subnet as theIAD’s WAN IP address. If the alias’s Internet IP address is on a subnetdifferent from the IAD’s WAN IP address, the proper subnet mask should beused. Refer to “Configure Port IP Address” on page 4-82 for furtherinformation.IP FilteringIP Filtering controls IP traffic traveling through an interface by selectivelypassing or discarding IP packets based on criteria expressed in the form of a
