Applicable Version: 10.6.1 onwards
The Domain Name System (DNS) is a system which translates domain names to IP Addresses and reverse of this i.e. translation from IP address to domain name is done by using reverse DNS. Given below is an illustration of how a DNS Request is resolved.
Types of DNS: There are two types of DNS using which translation of domain name to IP address can be done, one is static DNS and other one is Dynamic DNS.
Cyberoam allows you to create a Static DNS entry as well as you can configure Cyberoam as a DDNS (Dynamic DNS) server.
How DNS works:
Suppose, there is a website www.example.com with IP Address 10.10.10.1.
So, when a user accesses the website www.example.com, the steps given below are followed to resolve this domain name into an IP address:
1. Client sends request to Local DNS Server asking for the IP address of http://www.example.com.
2. Local DNS Server forwards this request to the Authoritative DNS Server.
3. The Authoritative DNS Server responds to the Local DNS Server with resolved IP addresses.
4. The Local DNS Server replies to the client with the IP Address (10.10.10.1) obtained from Cyberoam.
5. The Client then access www.example.com using the HTTP request http://10.10.10.1.
Cyberoam supports Static DNS Host Entry wherein Cyberoam acts as a DNS Name Server that provides the requesting client with 'A' or 'AAAA' records to resolve their requested URL. Also, multiple host entries can be added to a single domain.
This facilitates resolving of frequent DNS requests ay Cyberoam itself, and avoiding multiple cycles of the above mentioned DNS resolution cycles for every request.
This article instructs how you can configure Static DNS host entry.
Create a static DNS host entry for a website www.example.com such that when user accesses it, the DNS request is resolved by Cyberoam itself.
You must be logged on to the Web Admin Console as an administrator with Read-Write permission for relevant feature(s).
Step 1 : Resolve IP address for a domain name
You can find resolved addresses for any domain name using CLI of Cyberoam.
Steps that can be used to find resolved address for any domain name are:
• Logon to CLI Console via Telnet or SSH. You can also access the CLI Console by clicking on the Console button on the
upper right corner of the Web Admin Console screen.
From firmware version 10.6.1 onwards, the Console button is visible to theSuper Administrator ONLY.
• Choose option 4. Cyberoam Console.
• Execute the following command to check all the resolved IP addresses for a particular domain name
console > dnslookup host < domain name >
For example, if you want to find resolved IP address for a domain name www.example.com then executing the following command will find the resolved IP addresses for this domain name:
console > dnslookup host example.com
Step 2 : Configure Static DNS Host Entry
Go to Network > DNS > DNS Host Entry and click Add to add a DNS Host Entry.
Specify the IP Address 10.10.10.1 for the domain www.example.com and click OK to save the host entry as shown below:
So after above configuration of DNS host entry in Cyberoam, thesteps that will be followed when any user accesses the website www.example.com are:
2. Cyberoam checks DNS host entries for the requested website
3. Cyberoam replies to the client with the IP address found in the static DNS host entry for the requested domain.
4. The client then accesses the website using the resolved IP address i.e. 10.10.10.1
• A maximum of Eight (8) Address Mappings are allowed.
• Only A, AAAA, and PTR type of DNS records are supported.
• Address (A) record - points a hostname to an IP address and returns a 32-bit IPv4 address.
• AAAA record - points a hostname to an IP address and returns a 128-bit IPv6 address.
• Pointer records (PTR) - are just the reverse of A records and are used for reverse lookups. It maps IP address to a hostname.
• Maximum DNS entries supported – 1024
• If the appliance interface is used as a DNS in the Client system then a query is sent to the configured DNS servers prior to querying the ROOT severs.
The above configuration creates a static DNS host entry for a domain name.
Document Version: 1.0 – 29 May, 2015