Understanding Inbound Load Balancing
Inbound Load Balancing distributes inbound data traffic over multiple WAN links to computers/servers behind Peplink Balance. Peplink Balance 210, 310, 380, 580, 710, and 1350 have a built-in DNS server that enables this functionality.
Built-in DNS server functionality is not available on Peplink Balance 20 and 30.
Inbound Load Balancing is configured via both of the following:
- DNS records configured within Peplink Balance
All the records of the domain (A, MX, CNAME, TXT, etc) will be hold on Peplink. It is requried to modify the Name Server record (NS) on Domain Registrar in order to migrate from old DNS server to Peplink
- External DNS records at an Authoritative DNS Server
Delegrating the selected sub-domain to Peplink. For example: www.foobar.com, foobar.com will be hold on existing DNS server, only www.foobar.com will be hold on Peplink.
The following is a simplified example of an Inbound Load Balancing scenario when Peplink Balance is acting as an authoritative DNS server, further details subsequently follow:
- Peplink Balance is being an authoritative DNS server of domain foobar.com
- The web server that serves www.foobar.com is housed behind Peplink Balance, where Peplink Balance distributes the web server's data traffic across two WAN links (i.e. WAN1 and WAN2).
Both WANs are avaliable and traffic are load balanced.
In further detail, with the aforementioned DNS records, the following steps take place when resolving the hostname www.foobar.com:
- A client computer requires resolution for www.foobar.com, and queries the build-in DNS server of Peplink Balance for foobar.com
- The client computer queries, via WAN1, the DNS of Peplink Balance for the resolution of www.foobar.com.
In the event that the WAN1 connection is down, the DNS query would not succeed. However, as a built-in mechanism of the DNS protocol, the client computer then queries via WAN2 to resolve the hostname www.foobar.com
- Peplink Balance, upon receiving the DNS query, returns to the client computer the IP addresses of www.foobar.com that correspond to available WAN links. For example:
- If both WAN1 and WAN2 are available, then both the IP address that corresponds to WAN1 and that of WAN2 are returned.
- If WAN1 is available but WAN2 is down, then the IP address that corresponds to WAN1 is returned, but that of WAN2 is not returned.
WAN1 is down and incoming traffic goes through WAN2.
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