When looking at the ARP cache, that the ARP cache is only relevant to the local subnet. Hosts that are reachable across a router in a different subnet are reached using the arp cache entry for the server's default gateway.
Also, in the purest sense switches are layer 2 and ARP is a layer 3 protocol. The "show mac-address-table" command does not show a switch's arp cache. It shows the switch's forwarding table. You will not find IP addresses listed in the output of this command. In most layer 2 switches you will still find a "show arp" command but this will only show you the arp cache for the VLAN that the Management IP is a member of and it will only show you entries for hosts that have connected to the switch's Management IP. You will not see all hosts in that VLAN.
A layer 3 switch will use the same "show arp" command to show the arp cache and the "show mac-address-table" command to show the forwarding table. Layer 3 switches may have more entries depending on how routing and the management VLANs are configured.
Discussion on:
View:
Show:
I appreciate your comments and I did misput "show mac-address-table" when I meant "show arp". Great catch!
The "show mac-address-table" command on Layer 2 switches maps mac addresses to switch ports. It does not map ip addresses to mac addresses. Still useful, but for a different purpose. In a similar way, the arp table on a Layer 3 switch won't tell you what physical port the device is found on, just the vlan.
- Keyboard Shortcuts:
- Prev
- Next
- Toggle
