IBM Nortel Networks L2/3, Руководство пользователя

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