Router receives a frame/packet with unknown MAC address

[Ruterford]

Hi Everyone,

Lets assume that a router received a frame/packet on an interface due to switch did not have the destination mac address listed on its mac address table and therefore broadcatsed this packet out of all ports, and router receives that packet that was not even intended to reach it. Would the router route that packet or drop? Just wondering if my assumption is true and router would drop a frame/packet that it receives on an interface if the destination MAC address of this frame/packet is not a MAC address of the routers's interface that it was received on.

Thanks!

[Jon Marshall · Accepted solution]

Assuming it is a unicast packet then yes, your assumption is correct. 

The router would check the mac address against the mac address of the interface the packet was received on and if they did not match the packet would be dropped.

Jon

[pritishp333]

Hey but I don't think router ever does a destination mac check! (that's surprising indeed), looks like router does not check the destination information, until it strips off ip packet from the frame! have a look at what a router does when it receives a frame (with any destination mac addr) here:-

http://www.ciscopress.com/articles/article.asp?p=2244117&seqNum=2