Procurve 2650 - show arp

[Eric Nyman]

When I execute a show arp command, the only ip address that is displayed is the gateway address.

IP Address MAC Address Type Port
--------------- ------------- -----
10.90.24.1 0009b6-5ffg45 dynamic 49

If I physically ping a known ip address of a device that is connected to the switch (as an example, I will ping 10.90.24.236 which is a server that is on port 4), then that address will then appear after the show arp command is executed.

IP Address MAC Address Type Port
--------------- ----------------- -----
10.90.24.1 0009b6-5ffg45 dynamic 49
10.90.24.236 000d56-16c7r6 dynamic 4

Is there something I should do to make the ip/arp translate automatic without having to ping the address.

The configuration on this switch is basic with only two vlans.

[Eric Nyman]

I did find the show mac-address command but it would be nice to see the ip to mac relationship.

[Kell van Daal · Accepted solution]

Hi Eric,

What you are observing is standard behaviour.
The ARP table is indeed for ip - mac translation. So when does the switch itself need that information?
Right, only when the switch itself wants to send "something" to another node. And this usually isn't often if the switch does only switching and not routing.
The only entries in the arp table you would usually find are things like management stations (or the default gateway, if the management stations aren't on the same subnet) or the node you are telnetting/ssh'ing from.
When a switch does it core duty, namely switching, it does not look at layer 3 information such as the ip address, but only at layer 2 information such as destination and source mac addresses.
This is why the mac address table is complete. It's essential information for the switch.
So there isn't a way to fill the arp table automatically, asides from making a script that does a ping sweep originating from the switch.

If the switch was also setup as a router, and it would be the default gateway for all clients on that subnet, and all clients would at least once in a while communicate outside their subnet, then your arp table would get filled. But to change your network only for that seems like a lot of work for nothing ;)

[Ralph Bean_2]

Eric -

The usual way of getting a comprehensive list of end nodes and network devices, including their MAC-IP mappings, is through a network management application, not from a switch.

Ralph