The most common question we get is 'why don't I see IP addresses?'
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 switches
generally do not track/record/monitor IP addresses of connected devices unless
switch is a 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.
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 as well
(example Cisco 6509),
the ARP table may be larger depending on the size of the
network handled by the switch.
3. Two optional external SNMP enabled devices. If you are not using
Server/Router 1 or 2, please find an SNMP enabled router 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
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.
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. You can also
enter MAC/IP addresses one at a time manually.
We recommend Server/Router 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.