IBM L2/3 manual Guidelines for attaching the BladeCenter to a network, Guidelines and comments

7.3.4 Some important rules for ensuring High Availability

For High Availability (HA) to be truly effective it needs to be well thought out. A complete High Availability design should encompass servers, storage, and more of the network than just the portions connected to the BladeCenter chassis. The object is to ensure that there is no single point of failure which can cause the application(s) to become unavailable or unreachable.

The following are some important design considerations to try to ensure connectivity is maintained under various failure scenarios:

￿For NIC teaming to work properly with trunk failover, you must have external Layer 2 connectivity between the GbESMs. This can be done by cabling the GbESM modules directly to each other or by connecting them both to the same collection of upstream switches.

￿VRRP also requires a Layer 2 connection between switches. This connection must carry all the VLANs which have a VRRP instance configured.

￿To provide robust HA in a Layer 3 design:

–The two Nortel GbESMs should be configured with VRRP.

–The blade servers need to be using the VRRP address(es) for the VLANs where they are configured as their default gateway.

–It is possible to use VRRP (or equivalent) on the upstream switches as well to provide an even more robust HA design.

Note that the failure of a NIC within the blade server, the failure of a link between the GbESM and the blade server, and the hard failure of a GbESM would all result in a link down condition and would be successfully detected by NIC Teaming without the use of trunk failover.

7.4 Guidelines for attaching the BladeCenter to a network

This section contains information about things to consider when attaching the IBM Eserver BladeCenter to a network. We highly recommend that you review this entire section prior to any initial configuration changes. The topologies presented in this chapter discuss attaching the IBM Eserver BladeCenter to an external infrastructure.

7.4.1 Guidelines and comments

The following sections present comments and recommendations that are related to the various BladeCenter components which are used in the examples in this chapter.

Cable type selection (cross-over or straight-through)

Selection of the cable type (cross-over or straight-through) to use between the Nortel Networks L2/3 GbESM and an external switch is important. Although both a straight-through and a cross-over have been shown to work correctly in the lab during the creation of this document, there are certain times (such as when hard-coding link speed or duplex characteristics) when only a cross-over cable will work. Based on this, we strongly recommend that you use a cross-over cable between the Nortel Networks L2/3 GbESMs and upstream switches. This helps ensure that the link always works under all possible conditions.

Chapter 7. Nortel Networks L2/3 GbESM configuration and network integration 65