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Monitoring Tools 14-15
By default, the read-only and read/write community strings are set to public and private, respectively. You
should change both of the default community strings to values known only to you and trusted system adminis-
trators.
To change a community string, select it and enter a new value.
Starting with the version 4.3 firmware, setting the Read-Only and Read-Write community strings to the empty
string will block all SNMP requests to the router. (The router may still send SNMP Traps if those are properly
enabled.)
Previously, if either community string was the empty string, SNMP Requests specifying an empty community
string were accepted and processed.
This change is designed to allow the administrator to block SNMP access to the router and to provide more
granular control over the allowed SNMP operations to the router.
■ Setting only the Read-Write community string to the empty string will block SNMP Set Requests to the
router, but Get Requests and Get-Next Requests will still be honored using the Read-Only community string
(assuming that is not the empty string).
■ Setting only the Read-Only community string to the empty string will not block Get Requests or Get-Next
Requests since those operations (and Set Requests) are still allowed using the (non-empty) Read-Write
community string.
Even if you decide not to use SNMP, you should change the community strings. This prevents unauthorized
access to the Netopia 4753 through SNMP. For more information on security issues, see “Suggested Security
Measures” on page 13-1.
SNMP traps
An SNMP trap is an informational message sent from an SNMP agent (in this case, the Netopia 4753) to a
manager. When a manager receives a trap, it may log the trap as well as generate an alert message of its own.
Standard traps generated by the Netopia 4753 include the following:
■ An authentication failure trap is generated when the router detects an incorrect community string in a
received SNMP packet. Authentication Traps Enable must be On for this trap to be generated.
■ A cold start trap is generated after the router is reset.
■ An interface down trap (ifDown) is generated when one of the router’s interfaces, such as a port, stops
functioning or is disabled.
■ An interface up trap (ifUp) is generated when one of the router’s interfaces, such as a port, begins
functioning.
The Netopia 4753 sends traps using UDP (for IP networks).
You can specify which SNMP managers are sent the IP traps generated by the Netopia 4753. Up to eight
receivers can be set. You can also review and remove IP traps.
To go to the IP Trap Receivers screen, select IP Trap Receivers. The IP Trap Receivers screen appears.