Chapter 6 Configuring branch office tunnels 127Nortel VPN Router Configuration — Basic Featuresbranch offices are configured to use a domain name as a remote endpoint of theABOT tunnel. When two initiators at the remote sites need to establish a tunnel, aDNS query resolves the configured domain name ces.lab.com to the IP address.DNS returns 1.2.3.4 and 5.6.7.8 for branch one and 5.6.7.8 and 1.2.3.4 for branchtwo using Round Robin DNS. The initiator at branch office one uses 1.2.3.4 as aremote point because it was the first response in the list. The initiator at branchoffice two uses 5.6.7.8 as a remote point because it was the first DNS response inthe list.Figure 24 Load balancing exampleDynamic DNSDynamic DNS (DDNS) allows a dynamically addressed host computer to use astatic DNS name. The DNS name system is used both throughout the Internet andcorporations to provide both host to server and host to host communication formany applications. A DNS name space is typically set up by the systemadministrator. Increased use of dynamic IP-based Internet connectivity and theneed to publish well-known host names on the Internet has led to demand fordynamic DNS capabilities.The DDNS user is assigned a dynamic IP address, which may change every timethey connect. In general, the address rarely change because in most environments,users connectivity is outbound so there is no need to advertise a DNS name.However, users that host a Web server, FTP server, or game servers need toadvertise an address or DNS name to allow their clients to connect to the server.
