8. DNS Configuration

Overview

This chapter only applies to the Duolinks SW24 VPN Plus Load Balancer.

The Domain Name System (DNS) associates various information to a domain name. The primary function of a DNS server is to translate IP addresses into host names and host names into IP addresses (e.g. www.syswan.com translates to 72.167.0.118). A DNS Server stores all information related to a given domain name like a list of email servers, web servers or FTP servers. A DNS Server provides a name based redirection system which is an essential component of Internet activity today.

DNS configuration is necessary if you want to use Inbound Load Balancing mechanism in your network environment. You must know how to change IP addresses of your DNS servers at the registrar level (NIC) to point to public IP addresses of your load balancer WAN ports as follows :

Name server 1 : Public IP Address of your WAN 1

Name server 2 : Public IP Address of your WAN 2

After this registrar level update, your registrar will redirect to your Duolinks SW24 VPN Plus Load Balancer all DNS requests for your domain (e.g. A, NS, CNAME, MX). You will need to set the SOA resource records and configure DNS & Map Host URL pages in the DNS Configuration section to enable DNS response and to direct specific traffic to servers within your LAN.

Note that DNS propagation after a modification might take from 24 to 72 hours depending on the type of your TLD and your registrar.

Important Note :
You will need to check with your Internet Service Provider or your ISP service agreement documentation to make sure that there are no restrictions for hosting content on your WAN links.

Inbound Load Balancing diagram

DNS Setup

The above example shows a configuration where separate Public IPs are available for each LAN server. If you only have one Public IP per WAN port, the same Protocol/Port combination can only be sent out to one LAN server hosting multiple instances of the same service (example : one LAN server hosting multiple Web sites listening on TCP Port 80).

In order to make inbound load balancing work, you have to accommodate for servers on the LAN side of your Duolinks SW24 VPN Plus Load Balancer. It is also necessary for you to own or newly register at least one domain name. You will also need fixed public IP addresses for each of your WAN ports.

The Duolinks SW24 VPN Plus Load Balancer can host up to 6 SOA records (domains) and accommodate for 30 host URLs per domain (ie: www, ftp…).

Note :

Once you have registered your domain name and have the above server hardware structure installed within your LAN, you can configure inbound load balancing through the DNS setup pages as shown in the following example.

DNS Configuration Page

Settings – DNS Configuration

Setup Domain	Domain List – Supports up to 6 domains.
SOA (Start Of Authority) Record	· Domain Name/Primary Name Server – Fully qualified domain names (FQDN) eg. www.mydomain.com. It should terminate with a dot (.), otherwise the domain name will be added after it. · Admin. Mail Box – Email address for the domain administrator. You should use dot(.) to replace the at symbol(@) in the mail address. e.g. if Email address is super@mydomain.com. You should fill it as super.mydomain.com. · Serial Number/Refresh Interval/Retry Interval/Expiration /Minimum TTL – These are referenced in RFC1035. You may use the suggested default values.
TXT Record	· TXT Record – Enter SPF information or other required TXT data for the domain.
NS (Name Server) Record	· Pri. Name Server/Sec. Name Server – IP Address of your DNS server. · Public WAN IP Address – By default, this is: 0.0.0.0. This device will use the current WAN port IP address the same as DNS index. e.g. DNS1 Pri./Sec. Name Server used WAN1/WAN2, otherwise enter another public IP address provided by the ISP for the specific WAN port.
MX (Mail Exchange) Record	· Mail Exchange 1 and 2 – FQDN for primary and secondary mail servers. · Preference – Preference is the priority order, 0 being the highest priority. · Location/IP Address – Select Private and enter IP Address with its private address if the mail server is inside your LAN. Otherwise select Public and enter its public IP Address.

Map Host URL

After the setup of your DNS configuration, it is necessary to specify host URLs to map to the LAN IP addresses on your network. A FQDN (Fully Qualified Domain Name) is the combination of the host URL and the domain name (ie: www.mydomain.com).

Map Host URL Page

Settings - Map Host URL

A Record

· Host URL List – Select a URL to map to the IP address of a local host.

· Host URL – The URL to be mapped. If its value is "www" and domain name is mydomain.com. its FQDN is the combination of URL and domain name (www.mydomain.com.).

· Local IP Address – The IP address of local host.

· Port Number – The port number of all incoming packets are accepted and processed by a local host with the specified private IP address.

· Public WAN1/2 IP address – Used based on incoming load balance, if your ISP supports multiple static IP addresses for any WAN port; otherwise leave it blank. By default, it will use your current WAN port IP address for inbound load balancing.

CNAME Record

· Canonical Name – Alias for host URLs.

Host URL List

This lists the Host URL entries currently defined for a given domain.