Show IP address of specific port


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?

14 replies

Userlevel 4
Hey Ben,

You would want to run "show fdb " or "show fdb .

If this is an extreme switch on the other side, you can run "show edp"
Colatuno, Joe wrote:

Hey Ben,

You would want to run "show fdb " or "show fdb .

If this is an extreme switch on the other side, you can run "show edp"

"show fdb " gives me the mac addresses on that port but no IPs. "show fdb " also only returns the mac address as well as "show fdb ".

Is there another way?
Userlevel 4
Colatuno, Joe wrote:

Hey Ben,

You would want to run "show fdb " or "show fdb .

If this is an extreme switch on the other side, you can run "show edp"

try "show iparp " if there is an IP address on the vlan
If the other switch is an Extreme and they have common layer 3 management vlan between them then a show edp port (connecting port ) detail will show you the ip address of connected Extreme switch. If you know the mac address of that switch then you can also go to another switch/router and use that mac to find the arp entry.

One thing we have seen happen on some of the older XOS switches is they will loose their management and stop replying to polls but continue to pass traffic... This usually is the beginning of the end... If that is the case a reboot may bring it back but you need to look at code rev and upgrade if it is out of date... good luck !
EtherMan wrote:

If the other switch is an Extreme and they have common layer 3 management vlan between them then a show edp port (connecting port ) detail will show you the ip address of connected Extreme switch. If you know the mac address of that switch then you can also go to another switch/router and use that mac to find the arp entry.

One thing we have seen happen on some of the older XOS switches is they will loose their management and stop replying to polls but continue to pass traffic... This usually is the beginning of the end... If that is the case a reboot may bring it back but you need to look at code rev and upgrade if it is out of date... good luck !

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.
EtherMan wrote:

If the other switch is an Extreme and they have common layer 3 management vlan between them then a show edp port (connecting port ) detail will show you the ip address of connected Extreme switch. If you know the mac address of that switch then you can also go to another switch/router and use that mac to find the arp entry.

One thing we have seen happen on some of the older XOS switches is they will loose their management and stop replying to polls but continue to pass traffic... This usually is the beginning of the end... If that is the case a reboot may bring it back but you need to look at code rev and upgrade if it is out of date... good luck !

Sorry for all that then... I have 18 years being a purple user but zero on the E-800 series... If the switch that is not responding has to share a common subnet with something you can get to to see if there is an arp entry in the table for that mac address. If not it sounds like serial cable and console session time
Userlevel 2
EtherMan wrote:

If the other switch is an Extreme and they have common layer 3 management vlan between them then a show edp port (connecting port ) detail will show you the ip address of connected Extreme switch. If you know the mac address of that switch then you can also go to another switch/router and use that mac to find the arp entry.

One thing we have seen happen on some of the older XOS switches is they will loose their management and stop replying to polls but continue to pass traffic... This usually is the beginning of the end... If that is the case a reboot may bring it back but you need to look at code rev and upgrade if it is out of date... good luck !

Might try 'show neighbors' or 'show arp'
Also if you have console running you can search in compass on that switch on and perhaps pick out the ip address there.
"show fdb " gives me the mac addresses on that port but no IPs. "show fdb " also only returns the mac address as well as "show fdb ".

Is there another way?
Userlevel 2
You can try to enable cdp (on enterasys i think is enabled by deafult) and lldp and if it is enabled on the remote device you can see some information about it.
$up€®️bb¥ wrote:

You can try to enable cdp (on enterasys i think is enabled by deafult) and lldp and if it is enabled on the remote device you can see some information about it.

I have a little experience with 800-Series, I can confirm that you won't be able to see their ip address from the other switches on the same network unless you enable LLDP on the 800-Series. You can do it through webview, under "L2 Features" you should find "LLDP Global Settings" or something similar, then set LLDP state to "enabled" and Apply. This applies to 08H20G4 but I think it's similar on all 800-Series switches.
Userlevel 6
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.
Just a newbie here. But just wanna share some experience. Got the same scenario that i have the MAC-ADDRESS of the device and i wanna know the IP and Vice Versa. I tried to do show iparp on L2 switches but it did not show. So i tried it on our L3 core switch then i got the IP Address that i need and from there got all the information to locate the switch/port where the IP/Mac was connected. I'm still learning and wanna hear if maybe any better than my idea.
Userlevel 4
Nholy Raymundo wrote:

Just a newbie here. But just wanna share some experience. Got the same scenario that i have the MAC-ADDRESS of the device and i wanna know the IP and Vice Versa. I tried to do show iparp on L2 switches but it did not show. So i tried it on our L3 core switch then i got the IP Address that i need and from there got all the information to locate the switch/port where the IP/Mac was connected. I'm still learning and wanna hear if maybe any better than my idea.

Hello Norlito,

It's good to see people learning about networks. 🙂

IP ARP table is one of the approaches and it is a very good one. It would also work if you had an IP address on your switch and pinging the devices but... it's not the case, right?

When you're dealing with L2 devices they would have to introduce some additional features, as traditionally a switch doesn't care about what's inside an Ethernet frame.
Extreme has the solution! 🙂
It is called the node-alias table.
If you have EXOS device with firmware version 22.2 or newer, you might find this useful: https://documentation.extremenetworks.com/exos_22.5/EXOS_User_Guide_22_5.pdf (Chapter 6).
If you have EOS (ex-Enterasys) device, there is nodealias but for stackables (A/B/C series) you would have to use some SNMP manager application or an NMS system like Extreme Management Center to lookup the contents of relevant MIB. With more capable EOS switches (S/K/N) you can lookup the nodealias table directly on a switch.

Hope that helps.
Regards,
Tomasz
Nholy Raymundo wrote:

Just a newbie here. But just wanna share some experience. Got the same scenario that i have the MAC-ADDRESS of the device and i wanna know the IP and Vice Versa. I tried to do show iparp on L2 switches but it did not show. So i tried it on our L3 core switch then i got the IP Address that i need and from there got all the information to locate the switch/port where the IP/Mac was connected. I'm still learning and wanna hear if maybe any better than my idea.

Greetings Sir,

Thank you sir, I will try to look deeper on this additional knowledge 🙂

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