Typical Dns Resolver Application - Vpn Failover - Avaya G250 Administration

Basic device configuration
The most common application of this configuration is for connecting the G250/G350 to
the Internet and getting the DNS server information from the ISP. Therefore, interfaces
configured to automatically learn the DNS servers in the system are usually the Fast
Ethernet with PPPoE interface and the Dialer interface.
Typical DNS resolver application – VPN failover
In this typical application, the DNS Resolver feature is used to provide a VPN failover
mechanism between two main offices. The failover mechanism is implemented as follows.
The VPN branch office(s) connect to two main offices (the VPN remote peers) that are
configured with the same FQDN name, but have different IP addresses. When a branch office
makes a DNS query to resolve the VPN remote peer name to an IP address, it receives a list
with the IP addresses of both main offices, selects the first one, and builds a VPN tunnel with it.
If the first main office fails, the branch office sends another DNS query, and receives in reply the
IP address of the second main office. It will then start a VPN tunnel with the second main office.
This typical application is described in full in
Figure 3: VPN DNS topology
66 Administration for the Avaya G250 and Avaya G350 Media Gateways
Failover using DNS on page 423.