Cisco NM-8B-U - HW ROUTERS L-M User Manual page 21

16- and 36-port ethernet switch module for cisco 2600 series, cisco 3600 series, and cisco 3700 series
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16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series
MAC addresses are allocated sequentially, with the first MAC address in the range assigned to VLAN 1,
the second MAC address in the range assigned to VLAN 2, and so forth.
For example, if the MAC address range is 00-e0-1e-9b-2e-00 to 00-e0-1e-9b-31-ff, the VLAN 1 bridge
ID is 00-e0-1e-9b-2e-00, the VLAN 2 bridge ID is 00-e0-1e-9b-2e-01, the VLAN 3 bridge ID is
00-e0-1e-9b-2e-02, and so forth.
Default Spanning Tree Configuration
In
Table 4
Table 4
Feature
Enable state
Bridge priority
Spanning tree port priority (configurable on a per-interface
basis; used on interfaces configured as Layer 2 access ports)
Spanning tree port cost (configurable on a per-interface basis;
used on interfaces configured as Layer 2 access ports)
Spanning tree VLAN port priority (configurable on a
per-VLAN basis; used on interfaces configured as Layer 2 trunk
ports)
Spanning tree VLAN port cost (configurable on a per-VLAN
basis; used on interfaces configured as Layer 2 trunk ports)
Hello time
Forward delay time
Maximum aging time
Spanning Tree Port Priority
In the event of a loop, spanning tree considers port priority when selecting an interface to put into the
forwarding state. You can assign higher priority values to interfaces that you want spanning tree to select
first, and lower priority values to interfaces that you want spanning tree to select last. If all interfaces
have the same priority value, spanning tree puts the interface with the lowest interface number in the
forwarding state and blocks other interfaces. The possible priority range is 0 to 255, configurable in
increments of 4 (the default is 128).
Cisco IOS software uses the port priority value when the interface is configured as an access port and
uses VLAN port priority values when the interface is configured as a trunk port.
Spanning Tree Port Cost
The spanning tree port path cost default value is derived from the media speed of an interface. In the
event of a loop, spanning tree considers port cost when selecting an interface to put into the forwarding
state. You can assign lower cost values to interfaces that you want spanning tree to select first and higher
you can view the default Spanning Tree configuration values.
Spanning Tree Default Configuration
Default Value
Spanning tree enabled for all VLANs
32768
128
Fast Ethernet: 19
Ethernet: 100
Gigabit Ethernet: 19 when operated
in 100-Mb mode, and 4 when
operated in 1000-Mb mode
128
Fast Ethernet: 10
Ethernet: 10
2 seconds
15 seconds
20 seconds
Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ
Feature Overview
21

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