802.1Q Nonegotiate Trunk Configuration Example - Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual

Example VLAN Trunk Configurations

802.1Q Nonegotiate Trunk Configuration Example

This example configuration shows how to configure an 802.1Q Fast Ethernet trunk between two
Catalyst 4000 family switches with 802.1Q-capable hardware. (Use the show port capabilities
command to see if your hardware is 802.1Q-capable.)
In this example, an 802.1Q trunk is configured between port 1/1 on Switch 1 and port 4/1 on Switch 2.
The initial network configuration is shown in
both ends of the link.
Figure 11-4 802.1Q Trunking: Initial Network Configuration
4000
Switch 1
Step 1 To configure a port as an 802.1Q trunk, enter the set trunk command. You must use the nonegotiate
keyword when configuring a port as an 802.1Q trunk.
Switch 1> (enable) set trunk 1/1 nonegotiate dot1q
Port(s) 1/1 trunk mode set to nonegotiate.
Port(s) 1/1 trunk type set to dot1q.
Switch 1> (enable) 04/15/1998,22:02:17:DISL-5:Port 1/1 has become dot1q trunk
Switch 2> (enable) 04/15/1998,22:01:42:SPANTREE-2: Rcved 1Q-BPDU on non-1Q-trunk port 4/1
vlan 1.
04/15/1998,22:01:42:SPANTREE-2: Block 4/1 on rcving vlan 1 for inc trunk port.
04/15/1998,22:01:42:SPANTREE-2: Block 4/1 on rcving vlan 1 for inc peer vlan 2.
Switch 2> (enable)
Note
Figure 11-5 802.1Q Trunking: Port-Type Inconsistency
Trunk Type: 802.1Q
Trunk Mode: nonegotiate
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
11-18
Port 1/1 Port 4/1
Trunk Type: 802.IQ Trunk Type: 802.IQ
Trunk Mode: auto Trunk Mode: auto
After the port on Switch 1 is configured as an 802.1Q trunk, syslog messages are displayed on
the Switch 2 console, and port 4/1 on Switch 2 is blocked. STP blocks the port because there is
a port-type inconsistency on the trunk link: port 1/1 on Switch 1 is configured as an 802.1Q trunk
while port 4/1 on Switch 2 is configured as an ISL trunk (see
be blocked if it were configured as a nontrunk port.
Port 1/1
Trunk Type: 802.IQ
Trunk Mode: auto
Blocking
4000
Switch 1 Port-type
inconsistency
Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports
Figure 11-4. Assume that the native VLAN is VLAN 1 on
4000
Switch 2
Port 4/1
X
4000
Switch 2
Figure 11-5). Port 4/1 would also
78-12647-02