Layer 2 Interface Configuration Guidelines And Restrictions; Configuring Ethernet Interfaces For Layer 2 Switching - Cisco 4500M Software Manual

Chapter 12 Configuring Layer 2 Ethernet Interfaces
Table 12-3 Layer 2 Ethernet Interface Default Configuration (continued)
Feature
Native VLAN (for 802.1Q only
trunks)
STP
STP port priority
STP port cost
1. STP = Spanning Tree Protocol

Layer 2 Interface Configuration Guidelines and Restrictions

Keep the following guidelines and restrictions in mind when you configure Layer 2 interfaces:
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Configuring Ethernet Interfaces for Layer 2 Switching

The following sections describe how to configure Layer 2 switching on a Catalyst 4500 series switch:
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OL-6696-01
1
In a network of Cisco switches connected through 802.1Q trunks, the switches maintain one instance
of spanning tree for each VLAN allowed on the trunks. Non-Cisco 802.1Q switches maintain only
one instance of spanning tree for all VLANs allowed on the trunks.
When you connect a Cisco switch to a non-Cisco device through an 802.1Q trunk, the Cisco switch
combines the spanning tree instance of the native VLAN of the trunk with the spanning tree instance
of the non-Cisco 802.1Q switch. However, spanning tree information for each VLAN is maintained
by Cisco switches separated by a cloud of non-Cisco 802.1Q switches. The non-Cisco 802.1Q cloud
separating the Cisco switches is treated as a single trunk link between the switches.
Make sure the native VLAN for an 802.1Q trunk is the same on both ends of the trunk link. If the
VLAN on one end of the trunk is different from the VLAN on the other end, spanning tree loops
might result.
Disabling spanning tree on any VLAN of an 802.1Q trunk can cause spanning tree loops.
Configuring an Ethernet Interface as a Layer 2 Trunk, page 12-6
Configuring an Interface as a Layer 2 Access Port, page 12-8
Clearing Layer 2 Configuration, page 12-9
Layer 2 Interface Configuration Guidelines and Restrictions
Default Value
VLAN 1
Enabled for all VLANs
128
100 for 10-Mbps Ethernet LAN ports
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• 19 for 10/100-Mbps Fast Ethernet ports
• 19 for 100-Mbps Fast Ethernet ports
4 for 1000-Mbps Gigabit Ethernet ports
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2 for 10,000-Mbps 10-Gigabit Ethernet LAN ports
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Software Configuration Guide—Release 12.2(25)EW
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