Overview

IPv6 Static Routing Load Balancing is important to understand it conceptually, but in practice it's a risky technique.

Usually, static route load balancing should be avoided and a solution like a floating static route or a dynamic routing protocol should be preferred.

Load balancing can be useful when we want to have traffic flowing through our network more evenly. This can help from some devices being overburdened with traffic. At the same time, it provides an active route if one route should fail.

Pro Tip: When using Static Routing to Load Balance, the AD to the next hop must be equal.

IPv6 Static Routing Load Balancing Topology
Load Balance Topology

Even though the AD to the next hop may be the same for both routes, the complete path to the destination for one route can be less optimal than the other. This may (or may not) cause packets to arrive out of order.

TCP can re-sequence the packets, but this may cause performance issues based on network resources and network usage.

Some important protocols don't use TCP. VoIP, for example, uses UDP. UDP doesn't re-sequence packets so the delay caused by out of order packets may be unacceptable.

Configuration and Verification

For our lab we’ll use the following topology:

IPv6 Floating Static Route Topology
IPv6 Static Route Load Balancing Topology

Let’s begin by configuring and verifying a static route so R1 has a route to R-3’s Loopback 36 interface. A return route from R-3 to R-1 isn’t required because it’s directly connected.

R-1(config)#ipv6 route 2001:36::36/128 2001:13::3
  
R-1#sh ipv6 route static
S 2001:36::36/128 [1/0]
      via 2001:13::3

This looks good. We’ve got our Static route in the routing table with the default Administrative Distance of 1.

Let's ping the loopback from R-1 to R-3's Lo36:

R-1#ping 2001:36::36
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:36::36, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/8 ms

Fantastic. The primary route is set.

Next, let's configure another path from R-1 to R-3's Lo36. We'll configure this path also with an AD of 1. The result will allow us to load balance.

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