Cisco WS-C4003 Software Guide - Page 194
Q Nonegotiate Trunk Configuration Example
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Example VLAN Trunk Configurations Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports 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 Figure 11-4. Assume that the native VLAN is VLAN 1 on both ends of the link. Figure 11-4 802.1Q Trunking: Initial Network Configuration Port 1/1 Port 4/1 Trunk Type: 802.IQ Trunk Type: 802.IQ Trunk Mode: auto Trunk Mode: auto 43993 4000 Switch 1 4000 Switch 2 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 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 Figure 11-5). Port 4/1 would also be blocked if it were configured as a nontrunk port. Figure 11-5 802.1Q Trunking: Port-Type Inconsistency 43994 Port 1/1 Trunk Type: 802.1Q Trunk Mode: nonegotiate Port 4/1 Trunk Type: 802.IQ Trunk Mode: auto Blocking 4000 X 4000 Switch 1 Port-type Switch 2 inconsistency 11-18 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 78-12647-02