How does the bridge handle the frame without proper Mac

[CISSP_Candidate]

If a router doesnt have information in its table about the destination address, it sends out an ICMP error message to the sending computer indicating that the message could not reach its destinaion.

How about Bridge?
After broadcasting for the MAC, and if bridge still doesnt know where to forward the frame to, how does it do? Will it notice soure computer?
Thanks

[Jescoi]

the answer is ... no, sorry about that, but the switch won't do anything other then filter out the packet and not forward it.

after it timed out, the upper layer will simply send out an ARP to discover the new MAC address. The implication is that in order for your host to have the destination MAC address you must have either received a packet from the origin host or sent out an ARP request for it. The chance that your host sent out a unreachable or unrecognizable unicast mac address usually can only mean 3 things: 1 the dest. machine is down, 2. someone changed the switch or the table in the switch is gone 3. your cache is old (this is very slim, very slim). In either case, the host will simply send out another ARP request to find the new MAC address. If still not available, then the router will give you a destination unreachable.

Isn't OSI wonderful? every layer just help each other out as they usually would.

The layer 2 switch is designed to be a lean mean machine, its ONLY job is
1. learn new MAC address
2. forward packet or filter (do not forward) packet
3. prevent loop.

That is all.