IBM L2/3 manual Dynamic link aggregation Ieee 802.3ad Lacp

The Advanced Layer 2 topology offers a good compromise between performance and high availability. It is made up of dual GbESMs, each with two, 2-port aggregated links, going to a pair of Core switches, each Core switch joined to each other via a single link (simulating a Layer 2 network beyond the switches). The 2-port aggregation itself provides for higher performance and the second 2-port aggregation link provides for full redundancy on a connection-loss or a switch-failure situation.

In the examples presented in this chapter, the Core switches are always forced to be the Spanning Tree Root Bridges. Having the Root Bridge directly attached to the GbESM is not necessarily recommended in redundant configurations, as flow patterns can become less than obvious. But it is highly recommended to have the Root Bridge outside the BladeCenter.

Important: There is a high probability that any existing network will already have a desired switch configured as the root. It is very important that you understand the proper selection of the root bridge and that the GbESM not be allowed to become the root bridge. Allowing the GbESM to become the root bridge can result in sub-optimal data flow within the Layer 2 network.

Summary of disconnect procedure, to be performed for each example

When performing initial configurations or making changes to existing configurations that might have an impact on Spanning Tree (such as changing link aggregation), it is recommended that you leave connections un-cabled, or shut down, prior to making the configuration changes. This will reduce the likelihood of any temporary Spanning Tree loops and possible network-down conditions that might result in the process of adding or changing configurations.

￿Shut down the ports on GbESM_1 and GbESM_2

/oper/port EXT1/dis /oper/port EXT2/dis /oper/port EXT5/dis /oper/port EXT6/dis

￿Shut down the ports on Core1 and Core2

conf t

int range g0/1-2, g0/11-12 shut

7.7.1Dynamic link aggregation IEEE 802.3ad (LACP)

In contrast to the static trunks configured in 7.6, “Basic Layer 2 entry topology” on page 69, dynamic Link Aggregation Control Protocol (LACP) is used now for the connections GbESM_1 to Core1 and GbESM_2 to Core2. The additional cross connections, GbESM_1 ports EXT5-6 to ports G0/11-12 on Core2 and similar GbESM_2 ports EXT5-6 to ports G0/11-12 on Core1 are configured as LACP trunks as well, including IEEE 802.1Q tagging (VLAN 5 untagged/native). Remember to shut down the ports before starting the configuration changes as mentioned before.

82Nortel Networks L2/3 Ethernet Switch Module for IBM Eserver BladeCenter