Wednesday, July 23, 2008

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.

Tuesday, July 22, 2008

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

Sunday, July 20, 2008

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.

Thursday, July 17, 2008

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

Sunday, July 13, 2008

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)#



Tuesday, July 8, 2008

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.

Monday, July 7, 2008

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


Tuesday, July 1, 2008

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