InterMapper FAQs

Here are some questions that customers and evaluators often ask our Technical Support group about InterMapper network monitoring software. If you can't find an answer to your questions here, please contact us.

Does InterMapper handle changes to Daylight Savings Time (DST)?

Yes. Or more precisely, current versions of InterMapper will work properly as long as the underlying operating system and Java virtual machine have been updated to handle the change of Daylight Savings Time. InterMapper and RemoteAccess always use UTC internally, but use the underlying environment's time facilities to convert to the local time that's displayed in log files and chart data.

As long as your OS/JVM have been updated, InterMapper will continue to operate properly. We have received information that the following environments have been patched and/or updated.

MacOS X 10.4.5 and newer - Apple site
Windows Vista, XP SP2, W2K3, W2K - Microsoft site
Java 1.3.1_18, Java 1.4.2_11, and Java 5.0u7 - Sun's Java DST page
Linux and Unix - Using zdump and zic to determine/change DST settings
Solaris 8 and above - Sun Solaris DST page

Background Information

In the US, Daylight Savings Time will begin earlier and end later, starting in 2007 as mandated by the U.S. Energy Policy Act of 2005. Other countries are implementing similar changes. The patches above will ensure that your computer works properly with the US2007DST time changes.

Jennifer Mears wrote an interesting article on Network World that describes the interaction between network time servers and operating systems regarding the DST switch.

Can I ping a fixed IP address?

Yes. Choose Insert -> Device... to open the Add Device(s) window. Then enter one or more IP addresses or DNS Names. Click Choose... and select the Ping/Echo probe type. The devices will be added to your map, and will be pinged continually.

How can I get traffic from my router or switch?

In the Add Device(s)... window, enter the IP address or DNS Name of one or more of your routers/switches. Click Choose... and select the SNMP MIB-II probe type. Enter the SNMP version and the community string or authentication information. The devices will be added to your map, and their interfaces will be shown. InterMapper will query all the interfaces and collect traffic statistics.

Use the context menu to show the Status Window for a summary of the traffic on the interfaces. You can also create strip charts to keep a history of the traffic or any underlined value in the Status Window.

How do I monitor a Web server or other kind of server?

When you add a device (Insert -> Device...), enter the IP address or DNS name of the server. Then click the Choose... button to select one of the nearly 100 built-in probes. There are several probes that can monitor various aspects of HTTP, Mail, LDAP, DNS, and other kinds of servers.

My switches are always orange and showing lots of errors (or discards). Why?

We frequently hear of devices that appear to have high levels of discards and/or errors. They are usually orange on the map, and the pop-up window shows a message like this:

Reason: Discards = 738: [1] sc0

The most likely reason that InterMapper shows a high rate of discards from a device is that the device is actually reporting these errors. It's common that when InterMapper reports errors (from its SNMP queries), the manufacturers' own monitoring tools will report zero errors. (It's also normal that the affected devices are operating normally, without problems, in this state.)

Experiments and Workarounds:

Use the vendor's own network monitoring tool (by telnetting in, using a web browser, etc.) to see if errors are being reported through the native management interface. It's possible that there actually is a problem.
This may be a bug in the SNMP implementation of the device. You can check with your vendor to see if there's a firmware upgrade that addresses the problem.
To test InterMapper's accuracy, use another SNMP console to check out the particular MIB variables for the device. InterMapper monitors the ifInDiscards and ifInErrors MIB variables (and the corresponding ifOutxxxx variables) listed on the Network and Server Probes page to compute its error & discard figures. You can monitor these same variables with your own SNMP Console to see if the same errors are reported there.
Examine the device's packet loss statistic in the Status Window.
- If packets are actually being discarded, you'll see a higher than normal packet rate of dropped packets.
- If packets aren't being dropped, it's another clue that the values reported by SNMP are incorrect.
As a workaround, if you've satisfied yourself that the error reports are bogus, you can instruct InterMapper to ignore the discards and/or errors. To do this, choose Set...Behavior and check the "Ignore Interface Errors" or "Ignore Interface Discards" box as desired.

How do I change the community string?

A device's SNMP community string can be changed through the Get Info window, or through a context menu.

To set the community string:

Select the devices for which you want to change the community string.
From the Monitor or Context menu, choose Set... Community.

Use this procedure to set the Read-Only community string for one or more devices at once.

What does it mean when InterMapper says a "subnet mask is discontiguous"?

A subnet mask should contain one bits in the "host part" (the left side of the mask) and zero bits on the right.

A subnet mask that has zero bits interspersed in the host part of the subnet mask is generally a configuration error. InterMapper points this out by turning the device orange: when you click and hold on a link, the status window will give a Reason: saying there are zeroes in the host part of the subnet mask.

Why do network labels sometimes have a "/2*"?

There's a problem with the subnet mask reported by the device. The /2* indicates that the subnet mask has zero bits in the host part.

Why won't a device connect to the proper subnet oval?

On an InterMapper map, devices attempt to connect themselves to a good subnet oval. (Each oval/subnet on a map contains one or more subnet ranges - that is, a range of IP addresses.) A device will attach itself by drawing a line to a subnet oval that contains its IP address.

If you add another subnet oval (Insert -> Add network...) with the same subnet, you can drag the line from one subnet to another.

If a device's link has been dragged to an oval that doesn't contain it's address, the link will jump back to another subnet that does.

If a device won't stay attached to a subnet that should contain its address, check the subnet mask of both the oval and the device. One may be misconfigured.

There are two separate network ovals on my map where I only expect one...

Examine the network status window (click and hold on a network, or select Status Window from the context menu) to determine whether the subnet masks are the same in both ovals. If the subnet masks are different, one of the devices connected to the oval with the "wrong" subnet mask may have a misconfigured subnet mask.

Note: For devices polled with ICMP echoes, InterMapper tries to guess whether it should draw a link to the network that contains the IP address. If both network ovals look equally good, it may draw a link to the "wrong" one, or alternate between them.

Some network ovals have more than one IP network number...

It's possible for a router or host to have two or more configured IP addresses for a particular interface.

It's also possible that InterMapper is only reporting what it has been told by the router, and the information it is using is incomplete. This may be true of multi-point network technologies (like frame-relay clouds). If you find a situation where InterMapper is reporting multiple networks on a logical network and you know it's wrong, please send us mail (InterMapper@dartware.com) so we can figure out a way to make InterMapper's depictions more accurate.

We would also like to hear about a network with multiple IP network numbers where InterMapper does not show them correctly.

Does InterMapper support unnumbered IP links?

Yes. By default, InterMapper does not display unnumbered interfaces for routers. It does display them by default for switches. To display unnumbered links:

From the Monitor menu choose the Set Info -> Set Behavior... The Set Behavior window appears.
Select the Display unnumbered interfaces check box.

What does it mean when a Status Window shows [[not in ifTable]]?

This is a normal situation for VLANs. InterMapper first traverses the ipAddrTable which maps IP addresses to ifIndex entries. It then looks for the interface description from the corresponding entries in the ifTable. If the VLAN has an entry in the ipAddrTable, InteMapper will display it as an unnumbered interface. However, that interface will not have an entry in the ifTable.

For example, the ipAddrTable might look like this:

ifIndex 1 --> 192.168.1.1/24
ifIndex 2 --> 192.168.2.1/24
ifIndex 3 --> 192.168.3.1/24

And the ifTable looks like this:

ifIndex 1 --> Ethernet 10/100
ifIndex 3 --> Ethernet 10/100

Then the interface description for ifIndex 2 will be listed as "[[Not in ifTable]]".

How can I find out how many devices I'm monitoring with InterMapper. Do I have to count all the boxes on each map?

The Server Information pane of the Server Settings window shows the number of devices you are monitoring.

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