IBM L2/3 manual Dynamic routing options OSPF/RIP, Merits of this configuration

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7.8.2 Dynamic routing options OSPF/RIP

This section discusses an enhancement to the Layer 3 configuration that is shown in 7.8.1, “Layer 3 sample configuration with static routing and VRRP” on page 109. Instead of using static routes to enable the switches to know how to reach the various subnets, standard dynamic routing protocols is used. In addition to the use of the dynamic routing protocols, this configuration has a slightly different topology than the one above, introducing two additional VLANs for connections between the GbESMs and the Core switches as well as a direct cross-connection between the two GbESMs.

The use of these protocols and this more complex topology allows a Layer 3 configuration which provides High Availability without requiring the use of VRRP. The instructions that follow assume starting from the configuration that is described in 7.8.1, “Layer 3 sample configuration with static routing and VRRP” on page 109.

Merits of this configuration

This configuration is robust and suited for environments requiring High Availability. Its behavior in two key failure modes is:

￿Switch failure

In the event of a switch failure, the second switch in the BladeCenter chassis will take on the functions of the failed switch. Upstream (Core1 and Core2 in the samples) switches updates their routing tables to reflect the absence of the connection to the failed switch and sends inbound traffic to the second switch. NIC teaming is used to ensure that traffic is sent by the server blades to the second switch.

￿Uplink failure

In the event of an uplink failure to the primary switch, upstream (Core1 or Core2) switches will update their routing tables and send traffic only to the second GbESM.

Outbound traffic will go to the primary switch and then through the crossover link to the secondary switch unless tracking and hot-standby are used to trigger a VRRP failover.

This sample configuration does not use hot-standby. Instead, it relies on the crossover

connection between the two GbESM modules to forward traffic between the two switches: the secondary switch, which connects the IBM Eserver BladeCenter to the outside world, and the primary switch, which continues to forward traffic to and from the server blades.

Chapter 7. Nortel Networks L2/3 GbESM configuration and network integration 125