MPLS Traffic Engineering to configure optimal load-balancing in a highly redundant environment (NIL IP Corner)

Perfect load-balancing: How close can you get? (NIL IP Corner)
In this article, you’ve seen how you can use MPLS Traffic Engineering technology to configure optimal load-balancing in a highly redundant environment. The configuration example focused on a simple scenario with two parallel links between sets of redundant routers, but you can easily use traffic engineering to load balance traffic between paths of unequal length or bandwidth. Even more, Cisco IOS allows you to specify balancing ratio between the parallel tunnels.


LAN-to-LAN load-balancing in redundant setup


Server-to-server replication


Load-balancing with a single LAN gateway

Load-balancing with reduced WAN link cost

MPLS TE tunnel between A1 and B1


Load-balancing over MPLS TE tunnels



a1#show ip route

… parts deleted …

O 192.168.0.0 255.255.255.0 [110/51] via 0.0.0.0, 00:00:31, Tunnel1
[110/51] via 0.0.0.0, 00:00:31, Tunnel0
a1#show ip cef 192.168.0.0
192.168.0.0/24, version 17, epoch 0, per-packet sharing
0 packets, 0 bytes
tag information set
local tag: tunnel-head
via 0.0.0.0, Tunnel1, 0 dependencies
traffic share 1, current path
next hop 0.0.0.0, Tunnel1
valid adjacency
tag rewrite with Tu1, point2point, tags imposed: {}
via 0.0.0.0, Tunnel0, 0 dependencies
traffic share 1
next hop 0.0.0.0, Tunnel0
valid adjacency
tag rewrite with Tu0, point2point, tags imposed: {17}
0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 0 packets, 0 bytes
The MPLS TE tunnels are unidirectional, so a corresponding set of tunnels has to be configured separately on B1 if you want to have optimal load-balancing in both directions.
Note
In most designs, you want to achieve optimized load-balancing in one direction only (from the server toward the clients).
If you want to load-share IP packets from the LAN to the two ingress routers for any reason or if you have further IP subnets attached to the LAN via additional routers, a set of tunnels has to be configured on A2 and B2 to reach a symmetrical bidirectional design where a packet is always optimally load-shared regardless of its direction or ingress router.

read the whole article @ NIL IP Corner