I had a switch "dissapear" from our network but it is still plugged in to the appropriate port. In short, the switch on that port has an IP, internet connectivity and packets can move between our vlans but I cannot ping the switch or the devices it's connected to. If I know the port and MAC, how do I look up it's IP from inside the extreme switch?
let me see if we can get a couple of things defined. First on the 800 that "disappeared" how were you managing it? Did you have an ip on that switch you were polling? if so then what does the route look like between your monitoring system and the 800? It has to share an ip to another switch/router somewhere for you to be able to manage it in the first place. If you were managing it from the management only port then the port that is connected to should be in a common broadcast domain/vlan that goes to your router interface or management subnet.. You should be able to look at that arp table and confirm you have an arp entry for the ip of the 800... I dont see how you would not know the ip of a device that you had been monitoring.
The other switch is an Enterasys 800 series so they do not share L3 management so show edp port returns nothing.
When you say "go to another switch and check the arp table" what do you mean? The main switch is a stack and this is an independent switch at a testing station. I've tried arp -a on the machine it's on and I only get the gateway address of the entire vlan and not the switch it's on.