The multi-VLAN port feature on Catalyst 2900XL/3500XL Switches allows you to configure a single port in two or more VLANs. This feature allows users from different VLANs to access a server or router without the implementation of inter-VLAN routing capability. A multi-VLAN port performs normal switching functions in all of its assigned VLANs. VLAN traffic on the multi-VLAN port is not encapsulated as it is in trunking.
Note: These are the limitations to the implementation of multi-VLAN port features:
- You cannot configure a multi-VLAN port when a trunk is configured on the switch. You can connect the multi-VLAN port only to a router or server. The switch automatically transitions to VTP transparent mode when the multi-VLAN port feature is enabled, which disables the VTP. No VTP configuration is necessary.
- The multi-VLAN port feature is supported only on Catalyst 2900XL/3500XL Series Switches. This feature is not supported on Catalyst 4500/4000, 5500/5000, or 6500/6000 Series Switches or any other Catalyst switches.
- Determine which port to configure as a multi-VLAN port.
Here, three VLANs are created on a Catalyst 3512XL Switch, and one port of the switch is connected to an external router. This example configures the port that is connected to the router as a multi-VLAN port.
In the example, port Fast Ethernet 0/1 is connected to an external router. For more information about how to create VLANs and assign ports to VLANs, see theConfigure the VLAN on Catalyst 2900XL, 3500XL, 2950, 2970, and 2940 Series Switches section of this document.6-3512xl#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ----------------------------- 1 default active Fa0/1, Fa0/3, Fa0/6, Fa0/7, Fa0/8, Fa0/9, Fa0/10, Fa0/11, Fa0/12, Gi0/1, Gi0/2 2 VLAN0002 active Fa0/2, Fa0/4 3 VLAN0003 active Fa0/5 4 VLAN0004 active 5 VLAN0005 active 6 VLAN0006 active - Configure the Fast Ethernet 0/1 port in multi-VLAN mode, and add assigned VLANs to the multi-VLAN port.
6-3512xl#configure terminal Enter configuration commands, one per line. End with CNTL/Z. 6-3512xl(config)#interface fastethernet 0/1 6-3512xl(config-if)#switchport mode multi !--- This command changes the port Fast Ethernet 0/1 mode to multi. 6-3512xl(config-if)#switchport multi vlan ? LINE VLAN IDs of VLANs to be used in multi-VLAN mode add add VLANs to the current list remove remove VLANs from the current list 6-3512xl(config-if)#switchport multi vlan 1,2,3 !--- This command assigns VLANs 1, 2, and 3 to multi-VLAN port Fast Ethernet 0/1. 6-3512xl(config-if)#^Z 6-3512xl#
- Issue the show interface interface_id switchport command and the show vlan command in order to verify the configuration.
6-3512xl#show interface fastethernet 0/1 switchport Name: Fa0/1 Operational Mode: multi !--- The port is in multi-VLAN mode. Administrative Trunking Encapsulation: isl Operational Trunking Encapsulation: isl Negotiation of Trunking: Disabled Access Mode VLAN: 0 ((Inactive)) Trunking Native Mode VLAN: 1 (default) Trunking VLANs Enabled: NONE Pruning VLANs Enabled: NONE Priority for untagged frames: 0 Override vlan tag priority: FALSE Voice VLAN: none Appliance trust: none 6-3512xl#show vlan brief VLAN Name Status Ports ---- -------------------------------- --------- ---------------------------- 1 default active Fa0/1, Fa0/3, Fa0/6, Fa0/7, Fa0/8, Fa0/9, Fa0/10, Fa0/1 Fa0/12, Gi0/1, Gi0/2 2 VLAN0002 active Fa0/1, Fa0/2, Fa0/4 !--- Note: Previously, port Fast Ethernet 0/1 was only in VLAN 1. !--- Now the port is assigned to multiple VLANs 1, 2, and 3. 3 VLAN0003 active Fa0/1, Fa0/5 4 VLAN0004 active 5 VLAN0005 active
- Issue the ping command from the switch to the router in order to verify the multi-VLAN operation.
The ping command receives a reply from the router each time the management IP address is assigned to any of the VLANs 1, 2, or 3.
6-3512xl#configure terminal Enter configuration commands, one per line. End with CNTL/Z. 6-3512xl(config)#interface vlan 1 6-3512xl(config-if)#ip address 192.168.1.1 255.255.255.0 !--- The management IP address is assigned to VLAN 1. 6-3512xl(config-if)#^Z 6-3512xl# 23:56:54: %SYS-5-CONFIG_I: Configured from console by console 6-3512xl#ping 192.168.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms 6-3512xl#ping 192.168.1.2 !--- You can ping the router from VLAN 1. Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/3 ms 6-3512xl#configure terminal Enter configuration commands, one per line. End with CNTL/Z. 6-3512xl(config)#interface vlan 1 6-3512xl(config-if)#no ip address !--- The management IP address is removed from VLAN 1. 6-3512xl(config-if)#shutdown 6-3512xl(config-if)#exit 6-3512xl(config)#interface vlan 2 6-3512xl(config-subif)#ip address 192.168.1.1 255.255.255.0 6-3512xl(config-subif)#no shutdown !--- The management IP address is assigned to VLAN 2. 6-3512xl(config-subif)#exit 6-3512xl(config)#exit 6-3512xl#ping 192.168.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/3 ms 6-3512xl#ping 192.168.1.2 !--- You can ping the router from VLAN 2. Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/202/1004 ms 6-3512xl#configure terminal Enter configuration commands, one per line. End with CNTL/Z. 6-3512xl(config)#interface vlan 2 6-3512xl(config-subif)#no ip address !--- The management IP address is removed from VLAN 2. 6-3512xl(config-subif)#shutdown 6-3512xl(config-subif)#exit 6-3512xl(config)#interface vlan 3 6-3512xl(config-subif)#ip address 192.168.1.1 255.255.255.0 6-3512xl(config-subif)#no shut !--- The management IP address is assigned to VLAN 3. 6-3512xl(config-subif)#exit 6-3512xl(config)#exit 6-3512xl#ping 192.168.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/3 ms 6-3512xl#ping 192.168.1.2 !--- You can ping the router from VLAN 3. Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/205/1004 ms
