Link Load Balancing Cheat sheet

Article #: Product Castle
KB-68 Unified Threat Management (Software and Hardware) Bamburgh onwards

What is Link Load Balancing?

Link Load Balancing (LLB) is used to combine the capacity of multiple external connections, and balance data requests across them proportionately:

It does not present multiple connections as one — that is known as Bonding and is not a function of Smoothwall. Bonding needs special equipment at both ends of the Internet connection so is something that an ISP might provide.

Which products can use this?

LLB is a feature of our UTM appliances (Software and Hardware). It can only be applied to external connections.

What are the benefits of Link Load Balancing?

When one connection goes down, another connection is assigned to take its place. This is known as Failover. As soon as those failed connections come back online they will be automatically reinstated via Failback. You can also set up Failover rules for each pool independently.

LLB works with traffic generated from services running on the Smoothwall itself, such as Guardian or Email relay (from the Anti-Spam module).

LLB fully supports all external connection types, including dynamic DHCP and PPPoE.

You can configure multiple load balancing pools if needed.

Are there any limitations?

If your Internet connection prevents our Connection monitoring function from reaching Google’s DNS, then monitoring must be turned off. Turning Connection monitoring off keeps a connection’s status as "up" even if it is not connected. This means that any data sent down this connection will be dropped if the connection is down.

If you set the bandwidth values of your external connections incorrectly, their ratios will be generated based on these incorrect figures. Smoothwall will always maximize the use of any active connection, so they will not be limiting their available bandwidth, but the distribution of data will not be optimal. Incorrect values also hinder management as they aren’t an accurate representation of available resources.


  • Link Load Balancing — A link load balancer, also called a link balancer, is a network appliance that distributes in-bound and out-bound traffic to and from multiple Internet Service Provider (ISP) links. See:
  • Link-load-balancer-link-balancer link — In telecommunications, a link is a physical (and, in some usages, a logical) connection between two points.See
  • Bonding — Bonding allows you to aggregate multiple ports into a single group, effectively combining the bandwidth into a single connection. See
  • Failover — A method of protecting computer systems from failure, in which standby equipment automatically takes over when the main system fails.
  • Failback — The process of restoring operations to a primary machine or facility after they have been shifted to a secondary machine or facility during failover. See
  • Pool — A pool is a group of external connections, and each pool has its own rules and ratios for failover and dividing bandwidth.

Refer also to our main Glossary.


Last updated: Author: Contributions by:
12 April 2017 Chris Humby