Cisco Switches: Difference between revisions
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To get active links: | To get active links: | ||
show int | include is up | show int(erface) | include is up | ||
show int(erface) fastethernet 0/20 | |||
To get MAC addresses: | To get MAC addresses: | ||
Revision as of 10:52, 10 February 2009
Useful commands:
To get active links:
show int(erface) | include is up show int(erface) fastethernet 0/20
To get MAC addresses:
show mac-ad show mac-ad | include Fa0/26 mac-ad | include 0800.3e26.1a04
NOTE: should be no 'Half duplex' connections, check it with command:
show int | include Half
If any exist, change it to the Full duplex:
mmm
Configure the VLAN on Catalyst 2900XL, 3500XL, 2950, 2970, and 2940 Series Switches
Create VLANs and Ports
Note: The output that you see can be different from some of the command output that this section displays. The difference depends on the model of your switch.
Complete these steps in order to create a VLAN.
Decide whether to use VTP in your network.
With VTP, you can make configuration changes centrally on a single switch, and you can automatically communicate those changes to all the other switches in the network. The default VTP mode on the Catalyst 2900XL, 3500XL, 2950, 2970, and 2940 Switches is the server mode. Refer to Understanding VLAN Trunk Protocol (VTP) for more information on VTP.
Note: Issue the show vtp status command in order to check the VTP status on XL Series Switches.
3524XL#show vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 254 Number of existing VLANs : 5 VTP Operating Mode : Server !--- This is the default mode. VTP Domain Name : VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0xBF 0x86 0x94 0x45 0xFC 0xDF 0xB5 0x70 Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00
After you set and verify the VTP domain, begin to create VLANs on the switch.
By default, there is only a single VLAN for all ports. This VLAN is called default. You cannot rename or delete VLAN 1.
Issue the show vlan command in order to check the VLAN information.
3524XL#show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4,
Fa0/5, Fa0/6, Fa0/7, Fa0/8,
Fa0/9, Fa0/10, Fa0/11, Fa0/12,
Fa0/13, Fa0/14, Fa0/15, Fa0/16,
Fa0/17, Fa0/18, Fa0/19, Fa0/20,
Fa0/21, Fa0/22, Fa0/23, Fa0/24,
Gi0/1, Gi0/2
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 1002 1003
1002 fddi 101002 1500 - - - - - 1 1003
1003 tr 101003 1500 1005 0 - - srb 1 1002
1004 fdnet 101004 1500 - - 1 IBM - 0 0
1005 trnet 101005 1500 - - 1 IBM - 0 0
Issue this set of commands in privileged mode in order to create another VLAN:
3524XL#vlan database !--- You must enter into VLAN database in order to configure any VLAN. 3524XL(vlan)#vtp server Device mode already VTP SERVER. !--- You can skip this command if the switch is already in server mode and you !--- want the switch to be in server mode.
Note: A switch can only create VLANs if it is in VTP server mode or VTP transparent mode. Refer to Understanding VLAN Trunk Protocol (VTP) for more information on VTP.
524XL(vlan)#vlan ? <1-1005> ISL VLAN index
3524XL(vlan)#vlan 2 ?
are Maximum number of All Route Explorer hops for this VLAN
backupcrf Backup CRF mode of the VLAN
bridge Bridging characteristics of the VLAN
media Media type of the VLAN
mtu VLAN Maximum Transmission Unit
name Ascii name of the VLAN
parent ID number of the Parent VLAN of FDDI or Token Ring type VLANs
ring Ring number of FDDI or Token Ring type VLANs
said IEEE 802.10 SAID
state Operational state of the VLAN
ste Maximum number of Spanning Tree Explorer hops for this VLAN
stp Spanning tree characteristics of the VLAN
tb-vlan1 ID number of the first translational VLAN for this VLAN (or zero
if none)
tb-vlan2 ID number of the second translational VLAN for this VLAN (or zero
if none)
3524XL(vlan)#vlan 2 name ? WORD The ASCII name for the VLAN
3524XL(vlan)#vlan 2 name cisco_vlan_2
VLAN 2 added:
Name: cisco_vlan_2
3524XL(vlan)#exit !--- You must exit from the VLAN database in order for the changes !--- to be committed. APPLY completed. Exiting.... 3524XL#
Note: The VTP mode can change from client mode to transparent mode if the switch attempts to learn or pass a greater number of VLANs than it supports. Always check that the switches that run in client mode support the same number of VLANs that the switches in server mode send.
Issue the show vlan command in order to ensure that the VLAN is created.
3524XL#show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4,
Fa0/5, Fa0/6, Fa0/7, Fa0/8,
Fa0/9, Fa0/10, Fa0/11, Fa0/12,
Fa0/13, Fa0/14, Fa0/15, Fa0/16,
Fa0/17, Fa0/18, Fa0/19, Fa0/20,
Fa0/21, Fa0/22, Fa0/23, Fa0/24,
Gi0/1, Gi0/2
2 cisco_vlan_2 active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 1002 1003
2 enet 100002 1500 - - - - - 0 0
1002 fddi 101002 1500 - - - - - 1 1003
1003 tr 101003 1500 1005 0 - - srb 1 1002
1004 fdnet 101004 1500 - - 1 IBM - 0 0
1005 trnet 101005 1500 - - 1
You can add ports (interfaces) in the newly created VLAN.
You must go to interface configuration mode for each of the interfaces that you want to add into the new VLAN.
Note: You can assign the ports of a Layer 2 Catalyst Switch to multiple VLANs, but the switch only supports one active management VLAN interface at a time and other switched virtual interfaces (SVIs) do not up/up because of Layer 2 functionality. Therefore, the switch supports only one active management Layer 3 address. On a Layer 2 Catalyst Switch, you can issue the optional management command under the new SVI in order to automatically shut down VLAN 1 and transfer the IP address to the new VLAN.
Switch#configure terminal
Switch(config)#interface vlan 2
Switch(config-subif)#management
Switch(config-subif)#^Z
Switch#show ip interface brief Interface IP-Address OK? Method Status Protocol VLAN1 10.0.0.2 YES manual up down VLAN2 20.0.0.2 YES manual up up FastEthernet0/1 unassigned YES unset up up FastEthernet0/2 unassigned YES unset up up !--- Output suppressed.
Issue this set of commands in privileged mode in order to add a particular interface in the VLAN:
3524XL#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
3524XL(config)#interface fastethernet 0/2
3524XL(config-if)#switchport access ? vlan Set VLAN when interface is in access mode
3524XL(config-if)#switchport access vlan ? <1-1001> VLAN ID of the VLAN when this port is in access mode dynamic When in access mode, this interfaces VLAN is controlled by VMPS
3524XL(config-if)#switchport access vlan 2 !--- These commands assign interface Fast Ethernet 0/2 to VLAN 2.
3524XL(config-if)#exit
3524XL(config)#interface fastethernet 0/3
3524XL(config-if)#switchport access vlan 2 !--- These commands assign interface Fast Ethernet 0/3 to VLAN 2.
3524XL(config-if)#end
3524XL# 00:55:26: %SYS-5-CONFIG_I: Configured from console by console
3524XL#write memory !--- This saves the configuration. Building configuration...
Issue the show vlan command in order to verify the VLAN configuration.
3524XL#show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/4, Fa0/5, Fa0/6,
Fa0/7, Fa0/8, Fa0/9, Fa0/10,
Fa0/11, Fa0/12, Fa0/13, Fa0/14,
Fa0/15, Fa0/16, Fa0/17, Fa0/18,
Fa0/19, Fa0/20, Fa0/21, Fa0/22,
Fa0/23, Fa0/24, Gi0/1, Gi0/2
2 cisco_vlan_2 active Fa0/2, Fa0/3
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 1002 1003
2 enet 100002 1500 - - - - - 0 0
1002 fddi 101002 1500 - - - - - 1 1003
1003 tr 101003 1500 1005 0 - - srb 1 1002
1004 fdnet 101004 1500 - - 1 IBM - 0 0
1005 trnet 101005 1500 - - 1 IBM - 0 0
Remove Ports or VLANs
In order to remove ports from the VLAN, issue the no switchport access vlan vlan_number command in interface configuration mode. After the port is removed from a VLAN that is not VLAN 1 (the default VLAN), that port is automatically added back to the default VLAN.
For example, if you want to remove interface Fast Ethernet 0/2 from cisco_vlan_2 (VLAN 2), issue this set of commands in privileged mode:
3524XL#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
3524XL(config)#interface fastethernet 0/2
3524XL(config-if)#no switchport access vlan 2 !--- These two commands remove interface Fast Ethernet 0/2 from VLAN 2.
3524XL(config-if)#end
3524XL#show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/4, Fa0/5,
!--- Note: Fast Ethernet 0/2 is added back to the default VLAN.
Fa0/6, Fa0/7, Fa0/8, Fa0/9,
Fa0/10, Fa0/11, Fa0/12, Fa0/13,
Fa0/14, Fa0/15, Fa0/16, Fa0/17,
Fa0/18, Fa0/19, Fa0/20, Fa0/21,
Fa0/22, Fa0/23, Fa0/24, Gi0/1,
Gi0/2
2 cisco_vlan_2 active Fa0/3
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 1002 1003
2 enet 100002 1500 - - - - - 0 0
1002 fddi 101002 1500 - - - - - 1 1003
1003 tr 101003 1500 1005 0 - - srb 1 1002
1004 fdnet 101004 1500 - - 1 IBM - 0 0
1005 trnet 101005 1500 - - 1 IBM - 0 0
In order to delete the VLAN, issue the no vlan vlan_number command in VLAN database mode. Interfaces in that VLAN remain a part of that VLAN and are deactivated because they no longer belong to any VLAN.
For example, if you want to delete cisco_vlan_2 from the switch, issue this set of commands in privileged mode:
3524XL#vlan database !--- This command enters you into the VLAN database mode.
3524XL(vlan)#no vlan 2 !--- This command removes the VLAN from the database. Deleting VLAN 2...
3524XL(vlan)#exit APPLY completed. Exiting....
3524XL#show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/4, Fa0/5,
Fa0/6, Fa0/7, Fa0/8, Fa0/9,
Fa0/10, Fa0/11, Fa0/12, Fa0/13,
Fa0/14, Fa0/15, Fa0/16, Fa0/17,
Fa0/18, Fa0/19, Fa0/20, Fa0/21,
Fa0/22, Fa0/23, Fa0/24, Gi0/1,
Gi0/2
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
!--- Output suppressed.
Notice that port Fast Ethernet 0/3 is not displayed in the show vlan command output. The removal of VLAN 2 deactivates this port. Unless you add the port back in another VLAN, the port is neither displayed or usable.
3524XL#show interfaces fastethernet 0/3 FastEthernet0/3 is down, line protocol is down !--- Output suppressed.
In order to make the interface usable, you must ensure that it belongs to some VLAN. In the case in this section of the document, you must add interface Fast Ethernet 0/3 to the default VLAN (VLAN 1) in order to make this interface usable.
If you have the output of a show-tech support command from your Cisco device, you can use Output Interpreter ( registered customers only) in order to display potential issues and fixes.
Note: In the case of Catalyst 3550 Switches, you can still use the interface without the addition of the interface to a VLAN. However, you need to make that interface a Layer 3 interface. Refer to the Configuring Layer 3 Interfaces section of Configuring Interface Characteristics for more information on Layer 3 interfaces on Catalyst 3550 Switches.