Viewing all Hosts connected to a switch

[ChrisGiebner]

Hi all,

a customer of me wants to see which hosts (IP/MAC) are connected to a switch.

In detail:

They do "maintenance" during work-hours and want to see which hosts will be down if they do a reboot, so they can inform them. They use IMC and want to click on the switch in IMC and see which hosts are connected to which ports, including IP and MAC information, regardless if the switch does routing or not.

[Vince-Whirlwind · Accepted solution]

I use a switchport mapper for this, because it will do 3 queries and put all the info together for you:

1/ the mac-address table on the switch: tells you what MAC addresses are on which switchport
2/ The ARP table on the Layer3 "core": tells you which IP addresses belong to which MAC address
3/ DNS: tells you what hostanmes belong to which IP addresses

You can of course do all this manually, but a proper witchport mapper is way easier.

I assume IMC has this component built in somewhere.

[ChrisGiebner]

Thank you for your reply.

The manual way is well known to me and I've seen this feature in IMC but only for switches which do routing, as they have the ARP Table and can corelate it with local MAC-Addresses, but I couldn't find it for switches which don't do routing. This also makes sense to me, since the access-switches don't bother about IP, save for management purposes.

The customer also uses Clearpass with MAC-Auth, but this Appliance also can't do what my customer wants, even though it does know and authenticates every single device on the network.

Thank you again for your reply, I'll try your suggestion.

[Vince-Whirlwind]

I use Solarwinds. You give it the SNMP details of the Layer2 switch and the router and tell it where to query DNS and it puts it all together for you.

The Solarwinds tool I use is over 10 years old, I've never needed to update it, it does everything I want.
You can get it in the Solarwinds toolkit (it boasts of having 60 network management tools, but I think I only really use about half a dozen of them) which costs $2000, but there is a 14-day free trial I can see on their website for the switchport mapper.