Avaya G430 Manual page 75

DNS resolver features
The Branch Gateway supports the following DNS resolver features:
• Supports IPv4 and IPv6 — it can resolve a hostname to IPv4 and IPv6 addresses.
• Fully compliant with RFC1034, RFC1035, and RFC1123
• Maintains a global DNS database for all interfaces. The database is compiled using:
- Static (user-defined) DNS servers
- Automatically-learned DNS servers. DNS servers can be automatically learned by
the FastEthernet 10/2 interface when it is configured as a DHCP client or configured
for PPP. For more information on DHCP Client, see
page 205.
The most common application of this configuration is for connecting the Branch
Gateway 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 FastEthernet 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 the IP
address of the second main office in reply. It will then start a VPN tunnel with the second main
office.
Note:
VPN is supported in IPv4 only.
This typical application is described in full in
Administering Avaya G430 Branch Gateway
Note:
The following PPP interfaces can be configured to automatically learn the DNS
servers in the system:
• FastEthernet with PPPoE
• Dialer interface
Configuring the DHCP client
Failover using DNS on page 536.
Basic device configuration
on
October 2013 75