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Quick Start Guide For Uplinks Load Balancing


Zen Load Balancer has been supporting the uplinks or providers load balancing since version V2RC2 was released in February 2012.

This implementation is part of the 3-level load balancing method using route load balancing and is based on the application of Zen Load Balancer as the default gateway for a local area network to have access to a wide area network with several service providers.

This document pretends to give a brief understanding of uplinks load balancing with Zen Load Balancer and the necessary steps to implement this solution within the enterprise or general local networks.



In this case, we’ve two different ISPs to access to Internet: a fast-cabled RDSI router and a slower 3G router.

The network connection between the ZenLB and the routers has to be isolated networks, for this reason, we’ve provided two independent interfaces with the networks:

o through the eth1, accessing to the fast cabled RDSI.
o through the wlan0, a wireless access to the slower 3G router.

Note that the clients have to be under another isolated network, so we’ve chosen a configuration with the Zen LB as the default gateway (

With this implementation we’ve established a weighted algorithm, the RDSI router weighs 5 meanwhile the 3G router weighs 2.

The link load balancing isn’t perfect as the routes are cached. ZenLB doesn’t support a non-cached behaviour.



How could we implement this architecture with Zen Load Balancer? This section will show the easy way to perform this architecture with Zen LB.



The following information is shown the network interface configuration through the section Network > NICs. Note that we don’t need any configured gateway, as the communication is done directly to the routers.

eth0 –
eth1 – IP: Netmask:
eth2 – IP: Netmask:
wlan0 – IP: Netmask:

Default Gateway: –

With this configuration, we’ve established the Zen Load Balancer IP addresses and the correspondent network interfaces.



Now it’s time to create a new datalink farm using the interface in which the clients will request the outgoing connections to the internet (for this example, eth1), through the DSLB > Farms section, create here a farm with a descriptive name

After clicking Save button, the farm will be created.

Editing the global parameters of our brand new datalink farm we’ve to select the right algorithm to be used. In our case, we’ve to select the Weight Algorithm to be balanced the both uplinks according to the weight value of each uplink.

>Also, a Priority Algorithm could be used to build an active-passive fault tolerance uplink balancer with different providers.

Finally, we’ve to configure our backends. For uplinks load balancing the real servers will be the routers that supply the real access to the internet with the correspondent interface and weight or priority value. The routers IP of the RDSI should be accesible directly through the eth1 and 3G through wlan0, those IPs are the backends for the Uplink farm.


Datalink farms creation will become Zen Load Balancer as a gateway between different network subnets and provides to a local LAN accessing to a high availability WAN.

For this reason, the network panel will show a lock gateway configuration for the “listening” network interface.

Now, we’ve internet link balanced! Accessing to a streaming video service to watch our favorite Coldplay video, we’ll be able to view the line consumption for every uplink interface through the View Backends Status section.

In this case, we’re using the most weighted line, as expected.

To detect an offline or online of any uplink, a direct ping to the router is requested every minute.

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