what is the difference between sh arp and Sh mac-address table. One entery that is present in ARP will be it present in MAC-address table also. And one entery that is present in Mac will it present in ARP also?
The ARP table would be a cache of IP to MAC translations that the host has sent IP traffic to (recently - within cache timeout). For something like a switch, there should be ARP table entries for the switch interacting with telnet/SSH from its management address, or perhaps sending SNMP replies or traps to a NMS, or perhaps logging to a syslog server, etc.
The MAC table is what the switch uses to keep track of what MACs are known per port. This so a L2 frame that enters the switch, with a unicast MAC destination address, doesn't have to be flooded to all ports.
One way to understand the difference between the mac-address-table and the arp table is that the mac-address-table is used for layer 2 forwarding while the arp table is used for layer 3 forwarding. This difference in purpose helps explain the different way that these tables are built. The mac-address-table is built by examining the source mac address of every layer 2 frame entering the switch and making sure that this mac address is in the mac-address-table and adding it to the table if the mac address is not already in the table. The arp table is built when a layer 3 device wants to talk to some other layer 3 device (in the same subnet) and sends an arp request. If the target device responds then an entry is created in the arp table.
Another difference is that the default timeout for entries in the mac-address-table is much shorter than the default timeout for entries in the arp table. This can lead to situations where there is an entry in the arp table but no entry for that mac address in the mac-address-table. This can lead to unicast flooding as Joseph mentions.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...