Configuring ISL Trunks

Configuring ISL Trunks Note: The 1900 series switch supports only Inter-Switch Link (ISL) trunking. The 2900 series switch supports both ISL and Dot1Q trunking. The 2950 series switch supports only Dot1Q trunking. 1900 Series Switch 1900Switch(config)#int fa 0/26 Enters interface mode 1900Switch(config-if)#TRunk on Turns trunking mode on 2900 Series Switch 2900Switch(config)#int fa 0/1 Enters interface mode 2900Switch(config-if)#switchport mode trunk Turns port to trunking mode 2900Switch(config-if)#switchport trunkencapsulation isl Sets encapsulation type to ISL Note: Trunking can only occur on a Fast Ethernet port. A 1900 series switch has only two Fast Ethernet portsports A and B. These are defined as fa 0/26 and FA 0/27 in the command-line interface (CLI). Note: For any series switch, you must set trunk mode at both ends of the link for the trunk to become active.

Troubleshooting VLANs

Troubleshooting VLANs

2900Switch#show vlan	Displays the complete VLAN database
2900Switch#show vlan brief	Displays a summary of the VLAN database
2900Switch#show interfaces	Displays a summary of each interface, including speed and duplex settings
2900Switch#debug sw-vlan packets	Displays information about VLAN packets a router has received but is not capable of supporting

Erasing VLAN Configurations

Erasing VLAN Configurations

1900 Series Switch

1900Switch#delete vtp	Deletes all VLAN information from the switch and resets VTP parameters to the factory defaults
or
1900Switch(config)#int fa 0/2
1900Switch(config-if)#no vlan static 2	Removes interface from VLAN 2 and puts it back into default VLAN 1
1900Switch(config-if)#exit
1900Switch(config)#no vlan 2 name Engineering	Removes only VLAN 2 from database
1900Switch(config)#

2900/2950 Series Switch

2900Switch#delete flash:vlan.dat	Removes entire VLAN database from Flash memory Make sure there is no space between the colon (:) and the characters vlan.dat. You can potentially erase the entire contents of Flash memory with this command if the syntax is not correct
2900Switch#delete flash:
Delete filename [ ]? vlan.dat	Removes entire VLAN database from Flash memory
Delete flash:vlan.dat? [confirm]	Press the Enter key
2900Switch#
or
2900Switch#config t
2900Switch(config)#int fa 0/3
2900Switch(config-if)#no switchport access vlan 3	Removes port from VLAN 3 and reassigns it to default VLAN 1
2900Switch(config-if)#exit
2900Switch(config)#exit
2900Switch#vlan database	Enters VLAN database mode
2900(vlan)#no vlan 3	Removes only VLAN 2 from database
2900(vlan)#exit	Applies changes and exits VLAN database mode

Note:

For the 1900 series switch, removing a VLAN from the database does not reassign ports in that VLAN back to the default Management VLAN. You must also go into the specific interface and reassign the ports as well.

Note:

For any series switch, you cannot remove VLAN 1.

Assigning Ports Using the range Command (2950 Switch Only)

Assigning Ports Using the range Command (2950 Switch Only)

2950Switch(config)#int range fa 0/1 - 4	Enables you to set the same configuration para-meters on multiple ports at the same time. Note that there is a space before and after the hyphen
2950Switch(config-if-range)#switchport mode access	Sets all ports to access mode
2950Switch(config-if-range)#switchport access vlan 10	Assigns all ports to VLAN 10

Assigning Ports to VLANs

Assigning Ports to VLANs 1900 Series Switch 1900Switch#config t 1900Switch(config)#int e0/2 Moves to interface mode 1900Switch(config-if)#vlan static 2 Assigns this port to VLAN 2 1900Switch(config-if)#int e0/3 Moves to interface mode 1900Switch(config-if)#vlan static 3 Assigns this port to VLAN 3 1900Switch(config-if)#exit Exits interface mode 1900Switch(config)# 2900/2950 Series Switch 2900Switch#config t 2900Switch(config)#int fa0/2 Moves to interface mode 2900Switch(config-if)#switchport mode access Sets switchport mode to access 2900Switch(config-if)#switchport access vlan 2 Assigns this port to VLAN 2 2900Switch(config-if)#int fa0/3 Moves to interface mode 2900Switch(config-if)#switchport mode access Sets switchport mode to access 2900Switch(config-if)#switchport access vlan 3 Assigns this port to VLAN 3 2900Switch(config-if)#exit Exits interface mode 2900Switch(config)#

Creating Static VLANs

Creating Static VLANs

1900 Series Switch

1900Switch#config t
1900Switch(config)#vlan 2 name Engineering	Creates VLAN 2 and names it Engineering
1900Switch(config)#vlan 3 name Marketing	Creates VLAN 3 and names it Marketing

2900 Series Switch

2900Switch#vlan database	Enters VLAN database mode
2900(vlan)#vlan 2 name Engineering	Creates VLAN 2 and names it Engineering
2900(vlan)#vlan 3 name Marketing	Creates VLAN 3 and names it Marketing
2900(vlan)#exit	Applies changes and exits VLAN database mode
2900#

2950 Series Switch

2950Switch#config t	Enters global config mode
2950Switch(config)#vlan 10	Creates VLAN 10 and enters VLAN config mode for further definitions
2950Switch(config-vlan)#name Accounting	Assigns a name to a VLAN
2950Switch(config-vlan)#exit	Moves back to global config mode
2950Switch(config)#vlan 20	Creates VLAN 20 and enters VLAN config mode for further definitions
2950Switch(config-vlan)#name Sales	Assigns a name to a VLAN
2950Switch(config-vlan)#exit	Moves back to global config mode

Tip:

For the 2900 series switch, you must apply the changes to the VLAN database for the changes to take effect. You can also use the command apply in the VLAN database, which will apply the changes, but not exit the mode. Using the Ctrl+Z command to exit out of the VLAN database will not apply the changes to the VLAN database. You must use the command exit to exit the VLAN database and have the changes successfully applied.

Tip:

For the 2950 series switch, the use of the VLAN database is being phased out, in favor of creating VLANs in the manner demonstrated in the preceding command syntax. If you use the vlan database command at the 2950Switch# prompt, the 2950 IOS will tell you this but will still allow you to use commands the same as the 2900 series switch. Get used to this style; it is the method to be used on all future releases of switches.

Displaying VLAN Information

Displaying VLAN Information

1900 Series Switch

1900Switch#show vlan	Shows VLAN information
1900Switch#show vlan-membership	Shows which ports belong to which VLAN
1900Switch#show vlan 2	Displays information about VLAN 2 only

2900/2950 Series Switch

2900Switch#show vlan	Shows all VLAN status
2900Switch#show vlan brief	Shows all VLAN status in brief
2900Switch#show vlan id 2	Displays information of VLAN 2 only
2900Switch#show vlan name Marketing	Displays information of VLAN named Marketing only

Port Monitoring on a Cisco 2950 Switch

Port Monitoring on a Cisco 2950 Switch:

c3550(config)#monitor session 1 source ?
interface SPAN source interface
remote SPAN source Remote
vlan SPAN source VLAN
c3550(config)#monitor session 1 source interface fa0/1 - 3 rx
c3550(config)#monitor session 1 destination interface fa0/24


Switch# show monitor session 1