This tool allows for the browsing of the output of a 'SNMP Walk'. There are some unique features that set the tool apart from all others.
To start the SNMP Browser two bits of information are required. The first is the Host name or IP address. This must be filled into the box next to Host. The second bit of information is the Community you wish to query. The Community can be thought of as a password for the SNMP server. If the Community entered does not match that specified on the SNMP server the server will not respond to the query. To you, the client, it would appear as though the host does not have a working SNMP service. The server can be setup to support a number of communities. Depending on which is used in the request, depends on the data given to the user. The most common community used is 'public'.
For each 'root' of the SNMP tree the output is first obtained and then 'cleaned', before it can be viewed. This cleaning optimizes (reduces to a minimum) the depth of the graphical layout of the MIB tree. This makes browsing a lot quicker, reducing the number of items that have to be 'opened' to get the end of the tree without compromising the data. A value for a MIB is only present right at the 'end' of a 'branch'.
Due to the way MIB trees are constructed, the need to expand lots of branches in order to get the information needed about one branch is often very inconvenient. To make the browser more useful, the use of what we have termed 'inference' has been incorporated.
In the screen capture above you can see that the end of the interfaces.iftable.ifentry.ifadminStatus.2 has been selected. All grayed values are inferred values and if not used in the context of the selected item are inaccurate. In other words the MIB interfaces.ifTable.IfEntry.IfDesc does not have a value of 'eth0' (in fact it has no value at all), but interfaces.ifTable.ifEntry.ifDesc.2 (inferred from .ifAdminStatus.2) does. So in the example, we wanted to know what the status of interface eth0 is, and in this case it was 1, which means operational. But unless you had also expanded .interfaces.ifTable.ifEntry.ifDesc you would not know that 'eth0' was referring to the .1 MIB extension. Although very difficult to explain in words, those used to a graphical SNMP browser will find 'inference' very useful and all should find it intuitive.
The SNMP Browser also has the ability to attempt to write to the server. Simply click on the value and enter what you desire. Note that the server will have to be setup to permit writing. If it has not been configured, then the server will most lightly not permit it.
Table 9.1. Advanced SNMP Properties
| Enable Node Cleaning | This feature reduces the number of branches to a minimum. Without this feature being enabled, the number of clicks required to get to the end of a tree branch may be a lot more. |
| Enable Inference | Only the very ends of branches have values. Opening all the branches takes up a lot of screen space and/or time (click on all relevant nodes). Inference has been used to overcome these innate weaknesses in graphical SNMP browsers. This is done by showing values to branches that are not fully open, based on its relative position to the end branch that you have selected. Although a mouth full in words, it is extremely intuitive. |
| Inferred Cell Color | Cells showing inferred values have this color as their background. |
| Enable Write | If this feature is enabled then clicking on a cell will permit you to edit its value. A SNMP server will have to have been specifically setup to allow values to be changed, even if this is done not all values will be writable. The SNMP Browser cannot know whether writing is permitted until it makes the attempt to write the value. If the server does not permit the change an error message will be offered. |
| Timeout and Retries | The timeout is the amount of time (in seconds) the SNMP Browser will wait for a response from the server before re-sending the request. Once the number of resend attempts reaches the Retries value, the program assumes no response will be forthcoming and report an error to the user. |
| Base | This specifies the point in the tree from which the walk will start. To get the entire tree a start of .1.3 is often used. You could also limit the data by entering the part of the tree that you are interested in, i.e. system, would return all system MIB's. |
| Port | The TCP port to send the requests to, usually 161. |