Using Multi-Link with Server Pools in inbound traffic management

If you have configured Multi-Link, it can be used to improve Server Pool availability.

You can also use Multi-Link with just one server in the Server Pool to take advantage of dynamic DNS updates.

Figure: Multi-Link configuration for a Server Pool

As an addition to the basic configuration, the NetLinks and (optionally) the External DNS Server are also specified for the Server Pool.

When dynamic DNS updates are not used, Multi-Link is based on assigning an IP address for the Server Pool in each NetLink. The Server Pool’s DNS entry on the external DNS server must be configured with an IP address for each NetLink so that clients can access the servers through the different NetLinks. When the connecting client requests the IP address for the Server Pool’s DNS name, the DNS server sends the Server Pool’s DNS entry with the IP addresses on the different NetLinks. The client connects to one of these addresses and the NGFW Engine allocates the connection to one of the Server Pool members. If the first Server Pool IP address is unreachable, the client can connect to the Server Pool’s next IP address on a different NetLink (depending on the client application).

When dynamic DNS updates are used, the NGFW Engine updates the DNS entries automatically based on the availability of the NetLinks. When a NetLink becomes unavailable, the Server Pool’s IP address for that link is automatically removed from the DNS entry on the external DNS server. When the NetLink becomes available, the IP address is again automatically added to the DNS entry.