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Using Enterprise Edge Services 27

P0910464 Issue 01 Enterprise Edge Networking Operations Guide

Domain Name Service (DNS)

The domain name service (DNS) is the system within the Internet that maps names

of objects, usually host names, into IP numbers or other resource record values. The

name space of the Internet is divided into domains. The responsibility for managing

names in each domain is usually delegated to systems in each domain.

Enterprise Edge functions as both a gateway to the Internet and as a DNS proxy:

• Gateway: a system that links two different types of networks and enables them

to communicate with each other. Enterprise Edge is the gateway that links your

company’s network to the Intranet or Internet. Depending on your

configuration, you can let your workstations know that Enterprise Edge is your

Internet gateway.

Note:If your PC is a DHCP client under Enterprise Edge, you do not have to do

this.

• DNS Proxy – A Domain Name Service (DNS) proxy translates alphabetic

domain names into computer-readable IP addresses. For example, the domain

name www.nortelnetworks.com for the Nortel Networks web site can translate

to the IP address 192.177.5.18. After a domain name is translated into an IP

address, the workstations on your network can communicate with the web site.

Depending on the configuration of your system, you can let your workstations

know that Enterprise Edge is the DNS proxy.

When Enterprise Edge receives DNS requests from clients, it first checks its local

cache for name entries and records. If found locally, Enterprise Edge immediately

responds to clients. Otherwise, Enterprise Edge creates a new DNS request to the

remote Primary or Secondary DNS servers on behalf of the client. If the remote

DNS server responds with the requested records, they are forwarded to clients and

cached in Enterprise Edge.

Note: If your PC is a DHCP client under Enterprise Edge, you do not have to let

your workstations know that Enterprise Edge is your DNS server.

Guidelines for Using DNS

Consider the following guidelines when using DNS:

• If the Enterprise Edge DNS service is enabled, make sure that clients always use

Enterprise Edge as their DNS server.

• When it is disabled, set the DNS Server field in DHCP configuration to the

remote DNS server IP address. If DHCP service is also disabled in Enterprise

Edge, tell all clients to set the DNS server in their IP configuration to the remote

DNS server.

• The DNS proxy carries security features because it keeps all of the internal IP

addresses from external web servers.

• You are required to fill in the remote Primary DNS server IP address. See DNS

on page 84 for instructions.

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Avaya EE Networking Guide de l'utilisateur Page 27