• A Network Switch Mapping Solution

Problem: 'I see MAC addresses - why don't I see IP addresses or hostnames?'

The switch port mapper gathers MAC Addresses from the switch. If you only see MAC addresses (and few or no IPv4 addresses), please understand that most switches are layer 2 and generally do not track/record/monitor IP addresses of connected devices unless the switch is a layer 3 or core switch like a Cisco 6509 or a Nexus. In order to get the IP addresses, we gather ARP tables which we use to match MAC addresses to IP addresses, There is no magic IPv4 network protocol to ask for an IP given a MAC. The application collects ARP tables (MAC/IP associations) from a variety of sources:

1. Your computer - your local ARP table and through Ping Sweep - use Ping Sweep on the parts of your local subnet that you know are populated. More on Ping Sweep in 4 below. Make sure Query Local ARP Table is checked.

2. The switch(es) you are communicating with. If the switch is layer 2 only, the ARP table will be pretty small or completely empty. If it's layer 3, the ARP table may be larger depending on the size of the network handled by the switch. Make sure Query Switch ARP Table is checked.

3. Two optional external SNMP enabled devices. If you are not using Router/Server 1 or 2, please find an SNMP enabled router (or nearby layer 3 switch) to query that has visibility into the subnets and VLANs handled by the switch. Highly important to use one or more of these devices. Remember, they need visibility into the same subnets as the switch is processing.

4. Ping Sweep. Set Ping Sweep to operate over the range of IPs that are actually in use (especially important to only define the exact range on a 10.x.x.x network - do not waste time pinging known empty IP address ranges) does two things: 1) it prepopulates any other switches or routers with mac/IP ARP table combinations and 2) responding IPs are probed with NetBIOS to access the mac address given the IP - Windows and Apple Mac machines will often respond to NetBIOS queries. Enable Ping Sweep must be checked AND a Ping Sweep Range must be predefined.

5. Static ARP table imported through Database Maintenance. This is useful when you have a network with many static IP devices like networked printers, routers and switches - use Import ARP Table. You can also enter MAC/IP addresses one at a time manually with Add ARP Table Entry.

We recommend Router/Server 1 and 2 be a router or a server on the network segment the switch is serving. Those ARP tables are combined into a single ARP table for lookups (Database Maintenance/Combined ARP Table). ARP tables are used because there is no reliable protocol to get an IPv4 address given a MAC address. Note that the combined ARP table is cleared on exit, this is controllable in Global Settings.

No hostnames? hostnames come from a query to DNS through your operating system. No IPs - no hostnames.

Problem: I get error message "Switch Communications Failure - First SNMP Query. Switch IP ..." (a timeout) when trying to map my switch. It's strange because the app maps my other switches just fine!

Background: This error means that we tried to retrieve the device RFC1213-MIB::sysObjectID to find out what kind of switch it is and nothing came back - this is our very first SNMP query. If the switch or any SNMP device supports SNMP, it MUST respond with this value - it is a mandatory item.

Note: if it maps your other switches, especially the same model switch, then the problem is settings - most likely in the switch but also possibly in the Switch Port Mapper.

Solution: The Switch Port Mapper presents you with a dialog box with things to check. Here is the list with some expanded explanations in italics. [SW] below means switch and [SPM] means this software. Same Switch Model Only: It can also be a firmware revision issue - check the firmware rev of the switch that does map and see if it is the same as the switch that does not map.

Check your settings in the switch [SW] and this program [SPM]:
1. [SW][SPM] Is switch IP address correct? (Verify the switch IP address and make sure the IP address in the left control panel is the same - also try pinging the switch from a command prompt to ensure you can reach the switch from your computer)
2. [SW][SPM] Does the switch support the SNMP version you have chosen in Settings? (Use your web interface or CLI to verify that the switch has SNMP enabled and the version(s) you want to use are active. Confirm this in Left Control Panel/Switch Settings/Settings button/SNMP Version.)
3. [SW] Is SNMP enabled on the switch? (Use your web interface or CLI to verify that the switch has SNMP enabled)
4. [SW][SPM] Do you have the correct Community Name (SNMPv1/v2c) or Credentials (SNMPv3)? (Use your web interface or CLI to verify switch community name, then go into SPM Settings for the switch and verify)
5. [SW] Is this computer on the switch\'s SNMP IP access permission list? (sometimes called an access control list ACL - if your switch uses this and it's enabled, you will need to be on it in order for us to talk to the switch)
6. [SW] Does your switch have levels of user permissions? If so, do you have sufficient permissions? (some switch have as many as 15 levels of user permissions. If your switch uses permissions and they are enabled, be sure that you have permission to read all switch OIDs using SNMP)

SNMPv3: If you are trying to use SNMPv3 and it is not working, then revert back to SNMPv2c or even SNMPv1 to make sure you can actually talk to the switch. You may have to turn on SNMPv1 or v2c using CLI or the web interface in order to test this.

Problem: Switch Port Mapper 2.x - Ping Sweep appears to go on forever or hang

Solution: It's not actually hanging - it's just busy, you need to check your Ping Sweep settings before starting a mapping and remember: the settings are saved specifically for each switch meaning one switch can have one range being pinged and another switch another range. If you are on a small network with a mask, the default range is 253 hosts - not a problem. But if you are on a 10.x.x.x network with a mask, the default range is huge and you have two options: 1. turn off Ping Sweep or 2. edit the range using the Ping Sweep editor to match the segments of the network you are actually using. There can be several ranges in Ping Sweep, not just one so be sure you are only pinging IP ranges that are actually used.

Note: the Ping Sweep on/off settings are saved with the Switch 'Group'. You can edit each switch group by clicking on Switch Lists, then on Edit Switch Group. A Switch Group is the unique combination of the IP addresses of the switch and any secondary servers/routers you are querying.

Problem: The status column is completely empty.

Solution: You have used the Column Order and Visibility Editor to change the columns, but when you did that you removed the ifIndex (Interface Index) column. Open the editor and put the ifIndex column back on the active columns (right) side. Close the editor and remap the switch. This was fixed in v2.35 so that the ifIndex column was made mandatory and cannot be removed from the results grid.

Problem: Switch Port Mapper 2.x - starting the app, exiting, restarting the app one or more times causes computer freeze on Windows 7 - 64 bit.

Solution: Running the app in Safe-Mode works fine. The problem is the video card drivers are out of date. Update the drivers from the video chipset manufacturer instead of through Windows Update. This is a rare problem only reported by one user.