Load Balancing in Router

Hi Firewall.cx brothers,

Hope everyone are doing fine. Well, I have just one question today.
How to does the load balancing works on router? How to configure load balancing on it? Does the HSRP can be used for this?

Appreciate your help on this. Thanks in advance.

Cheers!
Gagamboy

Hi gagamboy

basically, load balancing occurs when you have 2 or more routes in the routing table pointing to same destination network, were all those routes have the same Administrative Distance and the same Metric. In other words when the router has 2 or more choices, it can load balance, meaning that it will choose once route1, then route2, then route3 then again route1, then route 2 then.... and so on. Here is a brief look at how routing works:

1. When a packet arrives at a router and need to be routed. The most specific route is selected among all routes that cover the destination address of the packet.

2. If more than one route match then, the route with the lowest Administrative Distance is chosen.

3. If more than one route has the same AD, the route with the lowest metric is chosen.

4. If more than one route has the same metric, in this case, the router can load balance between the routes.

There are much more details to this than what I've said. I've only touched the surface. For example, there is also Unequal metric load balancing in EIGRP. Regarding HSRP, I'm really not the expert here. I hope others can help.

Thank you very much Solo, that was very detailed information.

I think that answers my question.

Hope we can hear from others what they think of load balancing and HSRP.

Thanks in advance.

Cheers!
Gagamboy

HSRP is not for load balancing, it's for fault tolerance. HSRP = Hot Stand-by Routing Protocol. If your primary router fails, the hot stand-by will take over.

Load balancing is accomplished by all routing protocols except for BGP, but they all approach it slightly differently.
EIGRP can maintain more than one route to a remote destination in it's topology table. If the routes have equal cost, load balancing will occur by default. EIGRP will also load balance across unequal cost paths too. To load balance across unequal cost paths, you need to alter the EIGRP Variance command. EIGRP will load balance across up to 4 equal cost paths by default. This can be increased to 6 by configuration. Bringing up the Variance command means that EIGRP will load balance across 4 UNequal cost paths by default, increasing to 6 if configured to do so.
OSPF and RIP can only load balance across equal cost paths, and like EIGRP, they will balance 4 paths by default, increasing to 6 if configured to do so.

And for router redundancy there's also a similar-but-different redundancy protocol called VRRP (Virtual Router Redundancy Protocol) that essentially does the same job

There is also the GLBP protocol that is for fault tolerance but can do load balancing.