Connectivity Solutions for the Cisco Unified Computing System
http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9402/white_paper_c11-623265.html
• You cannot configure Spanning Tree Protocol parameters, such as bridge priority and hello timers.
Ethernet Switching Mode
The Ethernet switching mode determines the way that the fabric interconnect behaves as a switching device between the servers and the network. The fabric interconnect operates in either of the following Ethernet switching modes:
• Switch mode
• End-Host Mode
Switch Mode
Switch mode is the traditional Ethernet switching mode. Use switch mode when the fabric interconnect is directly connected to a router, or when Layer 3 aggregation or a VLAN in a box is used upstream (Figure 32). Switch mode has the following attributes:
• The fabric interconnects run Spanning Tree Protocol with connected external switches to avoid forwarding loops; broadcast and multicast packets are handled in the traditional way.
• The fabric interconnects run Per-VLAN Spanning Tree Plus (PVST+), which cannot be changed to another Spanning Tree Protocol such as Multiple Spanning Tree (MST).
• You cannot configure Spanning Tree Protocol parameters, such as bridge priority and hello timers.
• MAC address learning and aging are enabled on both the server links and the uplinks, so that the switch operates like a typical Layer 2 switch.
• Some uplinks connected to external switches may be blocked by spanning-tree rules.
Also remember that you are limited to the options presented to you via the CLI and GUI. They should have the same capabilities. If you do not see an option for configuring spantree priortiy, changing the value is not supported.
HTH,
Dan Laden
