ARP vs mac-address-table

[Michal Valach]

Hi Guys,

I have one question. In my situation I have directly connected user PC to cisco switch. User is ping able but I do not see any arp entry and I have user MAC is in MAC-table. So how is switch resolving IP to MAC in this case? Why I do not see arp entry, but MAC address is in the table?

Thank you

[Talha Ansari]

From where to where are you pinging? Can you provide what ip addresses you have applied on the devices?

[cadet alain]

A switch works at Layer 2 so it doesn't need arp to map L3 address to L2 address for framing.

You are pinging your host from another host or router and the frame is forwarded through the switch with the mac-table.

Regards.

[Michal Valach]

I am pinging from the switch

[Talha Ansari]

Is the ip address of the switch which is used as source and the end user of the same subnet?

Did you see the arp entry for the switch mac-address in your pc?

[Jon Marshall · Accepted solution]

L2 switches usually only record mac-addresses. The only time a L2 switch records an IP to mac-address is when the switch has a management interface with an IP address and you are pinging to that address or from that address.

If you want to see the PC mac to IP mapping, find the PCs default-gateway, go on to that device and look at the arp table.

Jon

[Michal Valach]

Thank you all, especially Jon