Operating instructions

Chapter 7. Cisco Systems IGESM configuration and network integration 119
Ports that are part of an aggregation group
must have the same characteristics (speed,
duplex, trunk settings, carrying the same VLANs). Having ports with different characteristics
will result in unexpected issues, including aggregations failing to form between the Cisco
Systems IGESM and Cisco switches.
Examples in this chapter that show use of link aggregation are only in reference to layer 2 link
aggregation.
Options exist to control the way traffic is load-balanced over any aggregated links. This
section assumes that default load balancing is in use.
See “Default Etherchannel load balancing may not be optimal” on page 237 for procedures for
changing Etherchannel load balancing to something other than the default.
Spanning Tree
The Cisco Systems IGESM supports the current Spanning Tree IEEE standards (for example,
802.1D, 802.1s, 802.1w), as well as the original Cisco enhancements (PVST+) to Spanning
Tree, which allow for rapid convergence in the event of a switch or link failure. Current support
exists for up to 64 Spanning-Tree instances. As noted previously, the default for the Cisco
Systems IGESM is what is referred to as
Rapid-PVST, which makes use of 802.1w, instead of
the original Cisco extensions, such as UplinkFast and BackboneFast, to achieve rapid
recovery from a link or switchdown condition.
During the production of this document, at times it was necessary to make a change to an
STP port cost to ensure that the default flow of data was the preferred path rather than the
default path that STP allowed. As a quick comment on STP port cost, the following applies for
this document and the versions of code used:
򐂰 Default STP cost for single 1 Gbps link: 4
򐂰 Default STP cost for dual 1 Gbps EtherChannel (2 Gbps) link: 3
򐂰 Default STP cost for quad 1 Gbps EtherChannel (4 Gbps) link: 3
򐂰 Default STP cost for single 10 Gbps link: 2
򐂰 Default STP cost for dual 10 Gbps EtherChannel (20 Gbps) link: 1
For a more detailed discussion about Spanning Tree and its operation and configuration,
review the following document:
http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter0
9186a00801a6baa.html
BladeCenter HS20 NIC teaming considerations
NIC teaming is a server-based technology that is used to provide higher performance or gain
fault tolerance by eliminating single points of failure. Teaming enables the logical grouping of
physical NICs in the same server into a virtual adapter (or multiple virtual adapters).
Three distinct types of teaming are supported by the Broadcom Advanced Server Program
(BASP). The BladeCenter HS20 NICs only support the BASP teaming called
Smart Load
Balancing
(SLB, also known as Server Load Balancing) and SLB Auto-Fallback Disable. The
HS40 should also be able to support these and may be able to support two other options
Important: The links connecting the aggregation switches, 6500-1 and 6500-3 in this
document, are absolutely critical in the operation and health of the network. Based on this,
and as already noted, the links between these two switches should be spread over multiple
modules. This will help to ensure that a single module failure in either chassis will not take
this entire link down.