![[previous]](../../../graphics/l_arrow.gif){kind=icon}
![[next]](../../../graphics/r_arrow.gif){kind=icon}
Use these sections to identify and correct problems with communication between the management station and network devices:
If your management workstation cannot communicate with devices on the network, examine your management configurations for the devices and your management station configurations.
For information about Simple Network Management Protocol (SNMP), see "SNMP Operation".
If your management station or the devices that you manage are incorrectly configured for management, then the management station, which includes your Transcend® applications, cannot perform autodiscovery, polling, or SNMP Get and Set requests on the device.
If you have not configured port connections (including a possible out-of-band serial or modem connection) and have not created an administration password for access to the management agent, do so before you continue.
Examine your management configurations for any device that your management station cannot reach. Also examine your management station setup. If you can reach a device but are not receiving traps, first examine the trap configurations (the trap destination address and the traps configured to send). See "Configuring Traps" for more information.
Either modify device configurations so that they are the same as your management stations or modify the management station to match the configurations of your devices.
Verify that the following management configurations are correct:
How these parameters are configured can vary by device. For more information, see the user guide for each device.
Follow these steps:
1 . Ping the device.
2 . To test the IP address, Telnet into the device using an out-of-band connection.
3 . If Telnet does not work, connect to the device's console using a serial line connection and ensure that your device's IP address setting is correct.
4 . Using a management application, perform an SNMP Get and an SNMP Set (that is, try to poll the device or change a configuration using management software).
5 . If you cannot reach the device using SNMP, access the device's console and make sure that your SNMP community strings and traps are set correctly.
You can access the console using Telnet, a serial connection, or a Web management interface.
This section explains management configuration terms and provides additional conceptual and problem analysis detail.
Devices use IP addresses to communicate with the management station and to perform routing tasks. Assign a unique IP address to each device in your network. Choose each IP address from the range of addresses that are assigned to your organization.
The default gateway IP address identifies the gateway (for example, a router) that receives and forwards those packets whose addresses are unknown to the local network. The agent uses the default gateway address when sending alert packets to the management workstation on a network other than the local network. Assign the gateway address on each device.
The subnet mask is a 32-bit number in the same format and representation as IP addresses. The subnet mask determines which bits in the IP address are interpreted as the network number, which as the subnetwork number, and which as the host number. Each IP address bit that corresponds to a 1 in the subnet mask is in the network/subnetwork part of the address. This group of numbers is also called the Network ID. Each IP address bit that corresponds to a 0 is in the host part of the IP address.
The subnet mask is specific to each type of Internet class. The subnet mask must match the subnet mask that you used when you configured your TCP/IP software.
An SNMP community string is a text string that acts as a password. It is used to authenticate messages that are sent between the management station (the SNMP manager) and the device (the SNMP agent). The community string is included in every packet that is transmitted between the SNMP manager and the SNMP agent.
After receiving an SNMP request, the SNMP agent compares the community string in the request to the community strings that are configured for the agent. The requests are valid under these circumstances:
For more information about SNMP requests and community strings, see "SNMP Operation"
A device is difficult or impossible to manage if:
If community strings do not match, either modify the community string at the device so that it is the string that the management station expects, or modify the management station so that it uses the device's community strings.
Table 6 lists the default community strings for some common 3Com devices. Modify these default strings when you install a new device. You can use "Device View" to change community strings of most 3Com devices.
Community string settings are case-sensitive for all devices.
| 1
By default, no setting exists or is needed for initial access on this device.
|
Although community strings are SNMP's way to secure management communication, these strings appear in the SNMP packet header unencrypted and are visible if the packet data is analyzed. For this reason, change community string settings frequently to improve management security.
If your platform or management applications do not report events for some devices, then SNMP trap reporting may not be configured correctly for those devices.
If you find that traps are overwhelming your management workstation, you can filter out (disable) some common traps so that the management station does not receive them. Most devices allow you to select which traps to send to a management station IP address.
You can use "Device View" to change the trap reporting configuration of most 3Com devices.
See "Trap Reporting" for more information.