10-Strike Network Diagram FAQ: SNMP Issues, Saving MIB Tree Dumps

Q: I have scanned the network; the computers have been found, but connection lines (links) between them have not been drawn. Why is that?

A: To draw connection lines between the computers you will need manageable switches with SNMP enabled. When scanning a range of IP addresses SNMP agents are to be included in the range being scanned, proper community (passwords) are to be specified, and the option “Scan SNMP” is to be selected. The program must be allowed in your firewall. If you do not have such switches or, if SNMP is disabled, you will have to draw the links manually. This is not as scary and time consuming as it seems, you need to spend only several minutes.

If the program is unable to read the connection information from your switches for some reason, the connection links will not be drawn. Please perform the following steps before contacting our technical support staff:

1) Please check that the "Search SNMP devices..." option is selected and Community strings are correctly entered in Step 2 of the Scanning Wizard.

2) If you know the IP addresses and Community strings of your switches, select the "Retrieve a connection table from switches" setting and fill in the list of switches.

3) Check whether your switches appear in the table of found hosts in Step 3, and if they have the "SNMP agent present" option in the corresponding column.

If your switches are found and displayed in the search results, and they support the SNMP protocol but the links are still not drawn, please save a set of reports and send it to us. Perform the following steps:

1) Please start the Network Scanning Wizard.

2) Configure the necessary settings and scan your network. Please wait until the scanning process ends and you see the results window.

3) Save the scanning results to a file. Click the "Report" button and save the results to the Scan_Results_table.csv file. Close the Wizard window and cancel the map creation.

4) Save a full dump of your switch's MIB tree with the help of the SNMPWALK utility (please read below how to do this). Save separate dump files for different switches. Please include the switch's IP addresses in the filenames.

5) Please send the Scan_Results_table.csv file and the MIB tree dumps to our technical support staff via e-mail. Do not forget to specify the models and manufacturers of your switches. This will help us to detect the problem and add support for your switch model to our program.

Most likely, your switches do not contain the necessary data at all. In this case you can draw the missing links manually.

Q: My network map is not drawn automatically. How to detect IP address of my switch? How to enable the SNMP agent on it?

A: The program can draw connection lines between your computers only if the SNMP protocol is enabled on your switches.

1) First, you need to know the IP address range your switch belongs to or the switch's exact IP address.

How to find a switch on your network?

You can find a switch on your network using the snmpscan.exe utility (you can find it on the Internet). This is a free console application. But if the SNMP protocol is disabled on your switch, the program might not help you.

You can also try to search for switches by scanning a wide range of IP addresses with 10-Strike Network Diagram and looking at the results table. Find the "Network Adapter's Manufacturer" column and search for famous switch manufacturers (Cisco, HP, DLink, ...).

2) You need to know the community string of the switch (password). By default, it is "public".

3) The SNMP agent should be enabled in your switch.

How to enable the SNMP agent?

If you know IP address of your switch, you can try to open its web interface using a web browser (for example, http://192.168.1.1), enter a correct login and password, and change the SNMP settings. Turn on the SNMP agent on the SNMP settings web page. You can also configure a community string for SNMP access.

Q: The program does not see any hubs. How to enable the SNMP agent on hubs so the program would see them and draw connections?

A: Your hubs should support the SNMP protocol. You can find this out by searching the Internet by the hub name and model. If you fail to learn about the SNMP support on your hub model, you can send your hub name and model to us and ask about SNMP. Usually, hubs do not support SNMP. You need to have managed switches (Cisco, HP, DLink, Dell, etc.) on your network in order to draw connection links properly.

Q: The program cannot connect to a remote PC using the SNMP protocol. The SNMP service is started on the remote PC and the Community string is correct. What's wrong?

A: Probably the Windows Firewall blocks the program and the SNMP service. You need to add the program to the firewall exceptions on your PC (and the SNMP service should be allowed on the remote PC if the program still does not):

1) Click "Start", and then click "Control Panel". Double-click "Windows Firewall"

2) Click the "Exceptions" tab. Click "Add Program".

3) Locate the file SNMP service file NetworkDiagram.exe (in the program folder, inside "Program Files"), and then click "OK".
4) Click "OK".

Try to access the SNMP service again.

Repeat this for the SNMP service (the path should be something like this C:\WINDOWS\System32\snmp.exe) on the remote PC if the program still cannot connect to the service.

Q: The program scans the network slowly and hangs when I select the TCP port check on the Scanning Wizard window. Why is that?

A: This is because Microsoft introduces a limit (of 10) to restrict number of allowed simultaneous outgoing half-open TCP connections in Windows XP SP2(x86,x64)/SP3, 2003 Server SP1(x86)/SP2(x86,x64), Vista without SP(x86,x64) and with SP1(x86,x64) to prevent virus or malicious program to make unlimited infectious connections to other systems.

Learn more about this issue...

How to Save MIB Tree Dumps from Your Switches Using the SNMPWALK.EXE Utility

The SNMPWALK utility allows you to get a full dump of a SNMP device's MIB tree. The utility operates in the read-only mode and does not make any changes to the device's configuration. You can download SNMPWALK from many Internet sites. For example, you can download SNMPWALK here.

Please do not send MIB dumps made by other utilities to us.

How to save the MIB tree dump using SNMPWALK:

1) Unpack the program's archive to any folder. The archive contains some other SNMP utilities, but we will need the snmpwalk.exe file only.

2) Please run a command shell (cmd.exe) and change your current directory to a folder that contains the SNMPWALK files.

3) Type and run a command in the following format:

snmpwalk -v 1 -One -c comm_string ip_address iso > device_name.txt

Where:

comm_string = community string of the switch
ip_address = IP address of the switch
device_name.txt - filename for saving the dump. It would be helpful if you add the switch's model and IP address to the filename.

Example:

snmpwalk -v 1 -c public -One 192.168.1.100 iso > cisco-2950_192_168_1_100.txt

Please note (for Cisco switches):
You need to save a separate dump for each VLAN configured on the switch.
For example, a Cisco 3550 switch has three VLANs configured: 1, 5, and 150. You will need to run the snmpwalk command three times.

You can get the "cannot find module" error message during the utility operation. This is because the entire package has not been installed. Please ignore this message.

Please do not forget to use the -One and iso output options.

If the switch supports SNMPv2 and SNMP BULK requests, you can use the following command:

snmpbulkwalk -v 2c -One -c comm_string ip_address iso > snmpWalk_ip_address.txt

Example:

snmpbulkwalk -v 2c -One -c public 192.168.1.100 iso > cisco-3550_192_168_1_100.txt

4) All the saved dump files will be stored in the utility's folder. Please pack the saved files into a zip archive and send it to us.