Cisco 15327 - Manual (Page 122)

7-16
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 7 Configuring STP and RSTP
Default STP and RSTP Configuration
Default STP and RSTP Configuration
Table 7-5 shows the default STP and RSTP configuration.
Disabling STP and RSTP
STP is enabled by default on native VLAN 1 and on all newly created VLANs up to the specified
spanning-tree limit of 255. Disable STP only if you are sure there are no loops in the network topology.
Caution STP edge ports are bridge ports that do not need STP enabled, where loop protection is not needed out
of that port or an STP neighbor does not exist out of that port. For RSTP, it is important to disable STP
on edge ports, which are typically front-side Ethernet ports, using the command bridge
bridge-group-number spanning-disabled on the appropriate interface. If RSTP is not disabled on edge
ports, convergence times will be excessive for packets traversing those ports.
Caution When STP is disabled and loops are present in the topology, excessive traffic and indefinite packet
duplication can drastically reduce network performance.
Table 7-5 Default STP and RSTP Configuration
Feature Default Setting
Enable state Up to 255 spanning-tree instances
can be enabled.
Switch priority 32768 + Bridge ID
Spanning-tree port priority (configurable on a per-interface
basis—used on interfaces configured as Layer 2 access ports) 128
Spanning-tree port cost (configurable on a per-interface basis) 1000 Mbps: 4
100 Mbps: 19
10 Mbps: 100
STS-1: 37
STS-3c: 14
STS-6c: 9
STS-9c: 7
STS-12c: 6
STS-24c: 3
Hello time 2 seconds
Forward-delay time 15 seconds
Maximum-aging time 20 seconds