Cisco WS-C2980G-A Software Guide - Page 235

Default Trunk Configuration, Configuring a Trunk Link, Configuring an 802.1Q Trunk

Page 235 highlights

Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports Default Trunk Configuration • If you are connecting multiple Cisco switches to a non-Cisco 802.1Q cloud, all of the connections must be through 802.1Q trunks. You cannot connect Cisco switches to a non-Cisco 802.1Q cloud through ISL trunks or through access ports. Doing so will cause the switch to place the ISL trunk port or access port into the spanning-tree "port inconsistent" state and no traffic will pass through the port. • You are limited to 64 trunks that use nondefault trunk configurations, unless you use text file configuration mode. See Chapter 34, "Working With the Flash File System" for more information on text file configuration mode. Default Trunk Configuration Table 11-5 shows the default Fast Ethernet and Gigabit Ethernet trunk configurations. Table 11-5 Default Fast Ethernet and Gigabit Ethernet Trunk Configurations Feature Trunk mode Trunk encapsulation Allowed VLAN range Default Configuration auto dot1q (on hardware supporting 802.1Q only) normal-range VLANs 1-1005 and extended-range VLANs 1025−4094 Note A nondefault trunk configuration is a default trunk configuration with one or more extended-range VLANs removed from the trunk configuration. Configuring a Trunk Link The following sections describe how to configure a trunk link on Fast Ethernet and Gigabit Ethernet ports and how to define the allowed VLAN range on a trunk. Configuring an 802.1Q Trunk Note Some hardware does not support 802.1Q encapsulation. To determine whether your hardware supports 802.1Q, see your hardware documentation or use the show port capabilities command. Caution You must configure the ports on both ends of the trunk link as 802.1Q trunks using the set trunk command with the nonegotiate and dot1q keywords. Expect Spanning Tree Protocol (STP) to block the port on the other end of the trunk link until you configure that end of the link as an 802.1Q trunk as well. Do not configure one end of a trunk as an 802.1Q trunk and the other end as an ISL trunk or a nontrunk port. Errors will occur and no traffic can pass over the link. For more information, see the "Trunking Modes and Encapsulation Types" section on page 11-2. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 11-5

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11-5
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
Release 8.1
78-15486-01
Chapter 11
Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports
Default Trunk Configuration
If you are connecting multiple Cisco switches to a non-Cisco 802.1Q cloud, all of the connections
must
be through 802.1Q trunks. You
cannot
connect Cisco switches to a non-Cisco 802.1Q cloud
through ISL trunks or through access ports. Doing so will cause the switch to place the ISL trunk
port or access port into the spanning-tree “port inconsistent” state and no traffic will pass through
the port.
You are limited to 64 trunks that use nondefault trunk configurations, unless you use text file
configuration mode. See
Chapter 34, “Working With the Flash File System”
for more information
on text file configuration mode.
Default Trunk Configuration
Table 11-5
shows the default Fast Ethernet and Gigabit Ethernet trunk configurations.
Note
A nondefault trunk configuration is a default trunk configuration with one or more extended-range
VLANs removed from the trunk configuration.
Configuring a Trunk Link
The following sections describe how to configure a trunk link on Fast Ethernet and Gigabit Ethernet
ports and how to define the allowed VLAN range on a trunk.
Configuring an 802.1Q Trunk
Note
Some hardware does not support 802.1Q encapsulation. To determine whether your hardware supports
802.1Q, see your hardware documentation or use the
show port capabilities
command.
Caution
You must configure the ports on both ends of the trunk link as 802.1Q trunks using the
set trunk
command with the
nonegotiate
and
dot1q
keywords. Expect Spanning Tree Protocol (STP) to block the
port on the other end of the trunk link until you configure that end of the link as an 802.1Q trunk as well.
Do not configure one end of a trunk as an 802.1Q trunk and the other end as an ISL trunk or a nontrunk
port. Errors will occur and no traffic can pass over the link. For more information, see the
“Trunking
Modes and Encapsulation Types” section on page 11-2
.
Table 11-5
Default Fast Ethernet and Gigabit Ethernet Trunk Configurations
Feature
Default Configuration
Trunk mode
auto
Trunk encapsulation
dot1q
(on hardware supporting 802.1Q only)
Allowed VLAN range
normal-range VLANs 1–1005 and extended-range VLANs 1025
4094