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How can I host/delegate an Authoritative DNS domain on my Barracuda Link Balancer?

  • Type: Knowledgebase
  • Date changed: 8 months ago
Solution #00004131

Scope:
All Barracuda Link Balancer models, firmware version 1.2 and above

Answer:
The Barracuda Link Balancer can act as an Authoritative DNS server. This allows you to define one or more domains that are accessible via more than one WAN link, which provides two benefits:
  • Failover - If one WAN link goes down, the domain is still available using the other WAN link.
  • Incoming link load balancing - Incoming traffic to the domain will be spread across all links that you configure for that domain.
NOTE: Only WAN links with static IP addresses can be advertised to respond to DNS queries. However, you can accept traffic on any of your WAN links for a domain configured on the Barracuda Link Balancer.

To become an Authoritative DNS host:
  1. Set Authoritative DNS to Enabled.
  2. Click Enable next to each WAN link in the DNS Server Listen Links table. This table includes all WAN links with static IP addresses (configured on the Basic > Links page).
  3. Change the value for the Name Server or keep the default. This value is used as a label for NS records for all the hosted domains.
  4.  Click Save Changes.
Enabling a new DNS Server Listen Link:
  • If you enable a new DNS Server Listen Link (which is the same as adding a new Name Server) and there are already DNS domains defined, you will have to add a new NS record and a new A record to each domain.
To make the DNS root servers point to your domain:
  • If you haven't already registered your domain name, do that first with a domain name registrar like GoDaddy.com or register.com.   

    • If your domain name is already registered, contact your registrar to update the NS records of the domain to point to your static WAN IP addresses.

  • Create your domain using this page. This generates the SOA, NS and A records for your domain on the Barracuda Link Balancer.

Use the Domain section to create a new domain (or zone in DNS terminology).
  • Enter a new  Domain and TTL to create SOA (start of authority), NS, and A records for this domain. TTL (Time to Live) is the length of time that these DNS records may be cached. The format for TTL is a number followed by D for days, H for hours, W for weeks, or nothing for seconds. Examples: 30 (30 seconds), 3H (3 hours). Recommended for TTL: 2D (2 days). The SOA and NS records are given this TTL value but the A records' TTL is set to 30 (seconds). An A record is created for each matching domain name found in 1:1 NAT and Port Forwarding rules.
To host only a sub-domain:
  • If your domain is hosted at your ISP or elsewhere and you want to delegate a sub-domain to be resolved by the Barracuda Link Balancer, you will have to add some records to the zone file of the domain where it is stored at the registrar. If the domain is example.com, and you want to host my.example.com and you have two name servers ns1 and ns2, add these lines, using the actual IP addresses of your name servers:

    my      IN     NS     ns1
    my      IN     NS     ns2
    ns1     IN     A     216.101.241.181
    ns2     IN     A     192.0.2.2
  • Create the my.example.com. domain using this page. This generates the SOA, NS and A records for my.example.domain. on the Barracuda Link Balancer.
DNS Records
Use this section to add, view and update the DNS records that define your domain(s). You can also disable a domain by clearing the Enabled check box, but remember that it will take the TTL for a disabled domain's records to be deleted from DNS caches.
  • The DNS records are created with typical default values. You can see all of the values for each record and change them by clicking Edit next to the record in the DNS Records section.
  • Some records for Web servers are automatically added:

    • If the Barracuda Link Balancer has the firewall enabled and if you have added 1:1 NAT or Port Forwarding rules using a complete hostname (e.g my.example.com), some DNS records are automatically generated using the information in the rules. Check here to see what records have been added. You will need to create MX records for any mail servers.
To define a Web server:
  1. Click Add New Record next to the domain.
  2. Add an A record for your Web server.
To define a mail server:
  1. Click Add New Record next to the domain.
  2. Add an A record for your mail server.
  3. Click Add New Record next to the domain.
  4. Add an MX record for your mail server.
Additional Notes:
If the built-in firewall of the Barracuda Link Balancer is enabled:
  • When you create a new domain, the Barracuda Link Balancer looks for existing 1:1 NAT and port forwarding rules that include names in the Hostname field that have a domain suffix that is the same as the newly created domain name. Or, if you create a domain that is the same as your default domain (as specified on the Basic > IP Configuration page), the Barracuda Link Balancer looks for rules that have hostnames that do not appear to be fully qualified domain names. An A record for each matching rule, including both external and internal addresses, will be automatically created for each hostname.
  • In some cases, this mapping will not reflect your configuration. If your internal network clients fail to access a hostname, click Edit to edit the A record for the unresolved hostname. In the DNS Record page, in the IP Addresses table, add addresses to the Local Network column to be used in response to internal DNS queries.
If the built-in firewall of the Barracuda Link Balancer is disabled:
  • You can edit the A record(s) for any unresolved hostname. As described above, click Edit to edit the A record(s) for the unresolved hostnames. In the DNS Record page, in the IP Addresses table, add addresses to the Local Network column to be used in response to internal DNS queries.
Link to This Page:
https://campus.barracuda.com/solution/50160000000Hl9OAAS