Cisco CCNA

Applications and NAT

For most traffic. NAT only changes the source and destination addresses in the IP header and does not inspect or modify the data payload contained in the packet. Therefore, applications that carry source or destination IP addresses in the payload of the packet might fail to work because the IP header will be changed by NAT but the payload will be left unchanged. Aware that this could be a problem, Cisco has made and continues to make enhancements to NAT so it can inspect data payloads and support applications that are sensitive to translation. Contact Cisco and get the most recent list of these supported applications (enhancements to NAT occur with each software release). At the time of this writing. H.323, RealAudio. VDOLive. Vxtreme. CuSecMe (White Pine), NetBIOS over TCP/IP. NFS, rlogin, rsh, rep. and FTP are supported. Web (http), Telnet. NTP, and other applications that do not carry addresses in the data payload work fine with NAT—they do not require inspection of the data payload.