Cisco IOS Configuration Guide for Autonomous Cisco Aironet Access Points - Release 15.3(3)JE and later

SNMP Versions

This software release supports these SNMP versions:

• SNMPv1—The Simple Network Management Protocol, a full Internet standard, defined in RFC 1157.
• SNMPv2C, which has these features:

– SNMPv2—Version 2 of the Simple Network Management Protocol, a draft Internet standard, defined in RFCs 1902 through 1907.

– SNMPv2C—The Community-based Administrative Framework for SNMPv2, an experimental Internet protocol defined in RFC 1901.

• SNMPv3, which has these features:

– Support for SHA and MD5 authentication protocols and DES56 encryption.

– Three security levels: no authentication and no privacy (NoAuthNoPriv), authentication and no privacy (AuthNoPriv), and authentication and privacy (AuthPriv).

SNMPv3 supports the highest available levels of security for SNMP communication. Community strings for SNMPv1 and SNMPv2 are stored and transferred as plain text without encryption. In the SNMPv3 security model, SNMP users authenticate and join a user group. Access to system data is restricted based on the group.

You must configure the SNMP agent to use the version of SNMP supported by the management station. An agent can communicate with multiple managers; therefore, you can configure the software to support communications with one management station using the SNMPv3 protocol and another using the SNMPv2 or SNMPv1 protocol.

Table 18-1 lists the SNMP versions and security levels supported on access points.

SNMP Manager Functions

The SNMP manager uses information in the MIB to perform the operations described in Table 18-2 .

SNMP Agent Functions

The SNMP agent responds to SNMP manager requests as follows:

• Get a MIB variable—The SNMP agent begins this function in response to a request from the NMS. The agent retrieves the value of the requested MIB variable and responds to the NMS with that value.
• Set a MIB variable—The SNMP agent begins this function in response to a message from the NMS. The SNMP agent changes the value of the MIB variable to the value requested by the NMS.

The SNMP agent also sends unsolicited trap messages to notify an NMS that a significant event has occurred on the agent. Examples of trap conditions include, but are not limited to, when a port or module goes up or down, when spanning-tree topology changes occur, and when authentication failures occur.

SNMP Community Strings

SNMP community strings authenticate access to MIB objects and function as embedded passwords. In order for the NMS to access the access point, the community string definitions on the NMS must match at least one of the three community string definitions on the access point.

Note SNMP communities are used with SNMPv1 and SNMPv2c. SNMPv3 does not use communities.

A community string can have one of these attributes:

• Read-only—Gives read access to authorized management stations to all objects in the MIB except the community strings, but does not allow write access
• Read-write—Gives read and write access to authorized management stations to all objects in the MIB, but does not allow access to the community strings

Using SNMP to Access MIB Variables

An example of an NMS is the Cisco Prime Infrastructure network management software. Cisco Prime Infrastructure software uses the access point MIB variables to set device variables and to poll devices on the network for specific information. The results of a poll can be displayed and analyzed to troubleshoot internetworking problems, increase network performance, verify the configuration of devices, monitor traffic loads, and more.

As shown in Figure 18-1, the SNMP agent gathers data from the MIB. The agent can send traps (notification of certain events) to the SNMP manager, which receives and processes the traps. Traps are messages alerting the SNMP manager to a condition on the network such as improper user authentication, restarts, link status (up or down), MAC address tracking, and so forth. The SNMP agent also responds to MIB-related queries sent by the SNMP manager in get-request, get-next-request, and set-request format.

Figure 18-1 SNMP Network

For information on supported MIBs and how to access them, see Appendix B, “Supported MIBs.”

Default SNMP Configuration

Table 18-3 shows the default SNMP configuration.

Enabling the SNMP Agent

No specific CLI command exists to enable SNMP. The first snmp-server global configuration command that you enter enables the supported versions of SNMP.

You can also enable SNMP on the SNMP Properties page on the web-browser interface. When you enable SNMP on the web-browser interface, the access point automatically creates a community string called public with read-only access to the IEEE802dot11 MIB.

Configuring Community Strings

You use the SNMP community string to define the relationship between the SNMP manager and the agent. The community string acts like a password to permit access to the agent on the access point.

Optionally, you can specify one or more of these characteristics associated with the string:

• An access list of IP addresses of the SNMP managers that are permitted to use the community string to gain access to the agent
• A MIB view, which defines the subset of all MIB objects accessible to the given community
• Read and write or read-only permission for the MIB objects accessible to the community

Note In the current Cisco IOS MIB agent implementation, the default community string is for the Internet MIB object sub-tree. Because IEEE802dot11 is under another branch of the MIB object tree, you must enable either a separate community string and view on the IEEE802dot11 MIB or a common view and community string on the ISO object in the MIB object tree. ISO is the common parent node of IEEE (IEEE802dot11) and Internet. This MIB agent behavior is different from the MIB agent behavior on access points not running Cisco IOS software.

Beginning in privileged EXEC mode, follow these steps to configure a community string on the access point:

To disable access for an SNMP community, set the community string for that community to the null string (do not enter a value for the community string). To remove a specific community string, use the no snmp-server community string global configuration command.

This example shows how to assign the strings open and ieee to SNMP, to allow read-write access for both, and to specify that open is the community string for queries on all objects:

Specifying SNMP-Server Group Names

To configure a new SNMP group, or a table that maps SNMP users to SNMP views, use the following command in global configuration mode:

Configuring SNMP-Server Hosts

To configure the recipient of an SNMP trap operation, use the following command in global configuration mode:

Configuring SNMP-Server Users

To configure a new user to an SNMP group, use the following command in global configuration mode:

Configuring Trap Managers and Enabling Traps

A trap manager is a management station that receives and processes traps. Traps are system alerts that the access point generates when certain events occur. By default, no trap manager is defined, and no traps are issued.

Access points running this Cisco IOS release can have an unlimited number of trap managers. Community strings can be any length.

Table 18-4 describes the supported access point traps (notification types). You can enable any or all of these traps and configure a trap manager to receive them.

Some notification types cannot be controlled with the snmp-server enable global configuration command, such as udp-port. These notification types are always enabled. You can use the snmp-server host global configuration command to a specific host to receive the notification types listed in Table 18-4 .

Beginning in privileged EXEC mode, follow these steps to configure the access point to send traps to a host:

To remove the specified host from receiving traps, use the no snmp-server host host global configuration command. To disable a specific trap type, use the no snmp-server enable traps notification-types global configuration command.

Setting the Agent Contact and Location Information

Beginning in privileged EXEC mode, follow these steps to set the system contact and location of the SNMP agent so that these descriptions can be accessed through the configuration file:

Using the snmp-server view Command

In global configuration mode, use the snmp-server view command to access Standard IEEE 802.11 MIB objects through IEEE view and the dot11 read-write community string.

This example shows how to enable IEEE view and dot11 read-write community string:

SNMP Examples

This example shows how to enable SNMPv1, SNMPv2C, and SNMPv3. The configuration permits any SNMP manager to access all objects with read-only permissions using the community string public. This configuration does not cause the access point to send any traps.

This example shows how to assign the strings open and ieee to SNMP, to allow read-write access for both, and to specify that open is the community string for queries on non-IEEE802dot11-MIB objects and ieee is the community string for queries on IEEE802dot11-mib objects:

This example shows how to permit any SNMP manager to access all objects with read-only permission using the community string public. The access point also sends config traps to the hosts 192.180.1.111 and 192.180.1.33 using SNMPv1 and to the host 192.180.1.27 using SNMPv2C. The community string public is sent with the traps.

This example shows how to allow read-only access for all objects to members of access list 4 that use the comaccess community string. No other SNMP managers have access to any objects. SNMP Authentication Failure traps are sent by SNMPv2C to the host cisco.com using the community string public.

This example shows how to send Entity MIB traps to the host cisco.com. The community string is restricted. The first line enables the access point to send Entity MIB traps in addition to any traps previously enabled. The second line specifies the destination of these traps and overwrites any previous snmp-server host commands for the host cisco.com.

This example shows how to enable the access point to send all traps to the host myhost.cisco.com using the community string public :

This example shows how to enable the access point to send association traps with wireless client Mac address and autonomous AP IP address:

This example shows how to enable the access point to send disassociation traps with wireless client Mac address:

Note The association and disassociation traps only apply for wireless clients. The trap will be triggered when a wireless client associates or disassociates to the autonomous AP. Wired client will not trigger these two traps. By default, both the association and disassociation traps are disabled.

This example shows how to configure these SNMPv3 settings:

• a view name (iso)
• an SNMP engine ID (1234567890) that this agent uses to identify itself to the remote host at IP address 1.4.74.10
• an SNMPv3 group (admin) which supports privacy encryption, and all users of the group have read and write access to all objects defined in the iso view
• an SNMP user (joe) that belongs to the admin group, uses MD5 authentication for queries, uses xyz123 as a password for MD5, uses DES56 data query encryption, and uses key007 as an encryption key
• an SNMP user (fred) that belongs to the admin group, uses MD5 authentication for queries, uses abc789 as an encrypted password for MD5, uses DES56 data query encryption, and uses key99 as an encryption key

Note After you enter the last command in this example, the show running-config and show startup-config commands display only a partial SNMP configuration.