SNMP Management

With the SNMP  Management window, you can:

Note: In cluster configurations, some community strings are propagated by the command switch when a member switch joins the cluster. For details, see Propagated Community Strings.

Disabling and Enabling SNMP on a Standalone Switch

SNMP is enabled by default. It cannot be disabled on Catalyst 1900 and 2820 switches.

To disable SNMP on a 2900 or 3500 XL switch:

  1. On the SNMP Management window, deselect the Enable SNMP checkbox.
    If you decide to reenable SNMP later, select this checkbox.
  2. Click Apply to put your changes  in effect.
  3. Click OK to close the SNMP Management window.

Disabling and Enabling SNMP on a Switch Cluster

In cluster configurations, the command switch receives SNMP requests from the SNMP management station. The command switch  responds to the request sent directly to it, and it redirects requests sent to a member. The SNMP agent on the member switch processes the request and sends a response to the requester (the command switch), which transmits the response to the original requester (the management station).

SNMP is enabled by default. It cannot be disabled on Catalyst 1900 and 2820 switches. When SNMP is disabled on the command switch, SNMP applications are prevented from accessing the cluster, which makes bandwidth graphs unavailable.

Note: For Cluster Manager features to work properly, SNMP must be enabled with the community string set to "public."

To disable SNMP on a 2900 or 3500 XL switch:

  1. On the SNMP Management window, deselect the Enable SNMP checkbox.
    If you decide to reenable SNMP later, select this checkbox.
  2. Click Apply to put your changes in effect.
  3. Click OK to close the SNMP Management window.

Setting  System Options

System options are the administrative information that you can assign to a switch that helps identify it. Although SNMP allows a maximum of 255 characters for each System Options field, Cluster Manager software truncates this information to shorter lengths. For this reason, shorter entries are recommended (see individual steps in the following procedure for guidelines).

To assign system options:

  1. Select the System Options tab on the SNMP window.
  2. In the Name field, enter the host name of the switch.
    Host names must be unique. The maximum length of the host name on a command switch is 28 characters, and the maximum length of the host name on member switches is 31 characters.
    Note: Do not use "-N" (where N is a number) as the last characters in host names for any switch.
  3. In the Location field, enter the physical location of the switch.
    The maximum length of an entry in the System Location field is 129 characters.
  4. In the Contact field, enter the name or organization responsible for the switch.
    The maximum length of an entry in the Contact field is 129 characters.
  5. Click Apply to put your changes on this tab in effect.
  6. Click OK to close the SNMP Management window.

Propagated Community Strings

Community strings serve as passwords to authenticate SNMP messages. Each community string is either read-only (RO), which allows MIB-object information to be displayed, or read/write (RW), which allows MIB-object information to be displayed and modified. When a switch joins a cluster, the first read-only and first read/write community string from the command switch are propagated to the new member, and an @esN notation is appended to each propagated string. The N in this notation is a numeric identifier that is unique for each switch, and it can be up to two digits long.

On 2900 and 3500 XL switches, the propagated strings are the first read-only and first read-write community string listed on the SNMP Management window. On Catalyst 1900 and 2820 switches, the propagated strings are the last read-only and last read-write community string listed on this window. Because they are necessary for SNMP packet routing, these strings should not be removed on any switch.

In addition to the propagated strings, the SNMP configuration can also contain user-defined community strings.

Adding Community Strings

The command switch uses community strings to route SNMP packets to member switches. Catalyst 2900 and 3500 XL switches support an unlimited number of community strings of any length. Catalyst 1900 and 2820 switches support a maximum of four read-only and four read/write community strings that are up to 32 characters long. When you assign community strings to these switches, limit their length to 27 characters to accommodate the @esN identifier that will be appended (strings longer than 27 characters are truncated to 27 characters).

To add a new community string to a switch:

  1. Select the Community Strings tab on the SNMP Management window.
  2. In the New Strings field, enter a character string.
    Note: Limit the string length to 27 characters if the switch is a Catalyst 1900 or 2820 switch.
  3. Select the RO (read only) or RW (read/write) to specify the string type.
  4. Click Add to move the new community string to the Current Strings list.
  5. Click Apply to put your changes on this tab in effect.
  6. Click OK to close the SNMP Management window.

Removing Community Strings

When you remove a switch from a cluster, all @esN strings on the switch are removed. If the switch rejoins the cluster, the first read-only and first read/write string from the command switch are propagated to the member switch, and the @esN identifier is appended to each string.

Note: Do not remove the first read-only or the first read/write community string from a 2900 or 3500 XL switch; do not remove the last read-only or the last read/write community string from a Catalyst 1900 or 2820 switch. These strings are required for SNMP functions.

To remove an existing community string from the cluster:

  1. Select the Community Strings tab on the SNMP Management window.
  2. In the Current Strings list, select the community strings to be deleted.
    To remove all community strings, click Select All.
  3. Click Remove.
  4. Click Apply to put your changes on this tab in effect.
  5. Click OK to close the SNMP Management window.

If you remove a community string and enter a new one, click the Reload button on your browser to put the change into effect (click Refresh on Internet Explorer).

Note: If you do not reload or refresh the browser, using the Device Reports option produces an error.

Adding and Removing Trap Managers

A trap manager is a management station that receives traps, which are the system alerts generated by a switch. If a cluster member switch has no IP address, the command switch receives the SNMP traps and relays them to the trap manager. By default, no trap manager is defined, and no traps are issued.

Catalyst 2900 and 3500 XL switches support an unlimited number of trap managers, and community strings for the trap managers can be any length. On these switches, you can enable specific trap types for specific trap managers. Catalyst 1900 and 2820 switches support up to four trap managers, and community string length is limited to 32 characters. You cannot configure specific trap types for specific trap managers on these switches

To add a new trap manager:

  1. Select the Trap Managers tab on the SNMP Management window.
  2. In the New Manager section, enter the IP address of the new trap manager.
  3. Enter the community string for the new trap manager.
  4. Click Add to move your entry to the Current Managers list.
  5. Enable the trap types (for 2900 and 3500 XL switches only).
    Your selections send the following trap types to the new trap manager:
    Configuration: sends an SNMP configuration trap
    SNMP: sends an SNMP-type trap
    TTY: sends Cisco enterprise-specific traps when a Transmission Control Protocol (TCP) connection is closed
    VLAN-membership: sends SNMP VLAN Membership Policy Server (VMPS) traps
    VTP: sends SNMP VLAN Trunk Protocol (VTP) traps
    c2900/3500: sends SNMP 2900 XL or 3500 XL traps
    Note: These selections have no effect on Catalyst 1900 and 2820 switches.
  6. Click Apply to put your changes on this tab in effect.
  7. Click OK to close the SNMP Management window.

To remove an existing trap manager:

  1. Select the Trap Managers tab.
  2. In the Current Managers list, select the trap managers to be deleted.
    To remove all existing trap managers, click Select All.
  3. Click Remove.
  4. Click Apply to put your changes on this tab in effect.
  5. Click OK to close the SNMP Management window.