Table Of Contents
Task 1—Enabling SNMP in a Cisco IOS Device
About Enabling SNMP
Enabling SNMP
Task 1—Enabling SNMP in a Cisco IOS Device
About Enabling SNMP
In this case study:
•
Each Cisco IOS device is identified by a fixed and stable loopback IP address for network management purposes. The IP address functions as an device ID.
One block of loopback IP addresses is used to simplify IP-security filtering at the NOC. This technique protects the NOC from devices that should not access management services, such as TACACS+, RADIUS, syslog, and SNMP.
•The dial NMS environment interfaces with SNMP through these applications:
–UCD-SNMP
–SNMP Commander
–Multi-Router Traffic Grapher (MRTG)
–HP OpenView (HPOV)
–Cisco Works 2000 Resource Manager Essentials (CW2000 RME)
Caution Avoid using well-known community strings, such as "public," "private," or "cisco." These strings are easily guessed and leave your device open to malicious attacks or inadvertent access. To further enhance SNMP security, apply access lists to the community strings.
Enabling SNMP
To enable SNMP on a Cisco IOS device in the network, follow these steps.
Note In some software releases, the commands snmp-server engineID local and snmp-server packetsize are enabled by default.
Step 1 To use Loopback0 for device management and set SNMP traps to use that IP address, enter the following commands. This configuration also eliminates the need to change IP addresses if a different interface is used to send traps.
ip address 172.21.10.1 255.255.255.255
snmp-server trap-source Loopback0
Step 2 To enable a basic SNMP configuration, enter the following commands. See Table 13 for descriptions of each command.
snmp-server community 5urf5h0p RO
snmp-server community 5crapmeta1 RW
snmp-server location Lake Travis (Austin) Dial POP
snmp-server contact net-admin@aurora.the.net
snmp host 172.23.10.1 traps SNMPv1
Table 13 SNMP Command Descriptions
Command
|
Purpose
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snmp-server community 5urf5h0p RO
|
Assigns a read only (RO) community string. Only get requests (queries) can be performed.
The RO community string in this example (5urf5h0p) allows Get requests but no Set operations. The NMS and the managed device must reference the same community string.
|
snmp-server community 5crapmeta1 RW
|
Assigns a read write (RW) community string. SNMP applications require RW access for Set operations.
The RW community string in this example (5crapmeta1) enables write access to OID values. For example, you can shut down an interface, download a configuration file, or change a password.
|
snmp-server location Lake Travis
(Austin) Dial POP
|
Specifies the location of the device for administrative purposes.
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snmp-server contact admin
net-admin@aurora.the.net
|
Specifies a contact name to notify whenever a MIB problem occurs.
|
|
Enables traps for unsolicited notifications for configuration changes, environmental variables, and critical device conditions.
This command enables 14+ other commands for distinct types of SNMP traps. Edit this command list to include only the traps that are used by your network environment.
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snmp host 172.23.10.1 traps SNMPv1
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Identifies the host destination for the traps. Traps are sent in the SNMP v1 format in this case study.
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