Hello
The router can do a couple of things.
It will first strip the L2 Frame as that's only required to get to the router then it will check the L3 IP header dest address and to see if it is or not for itself, If isn't it will look up the dst address in it own rib /arp tables and if it has a match it will recreate a l2 frame encapsulate the packet and send it on its way towards the nexthop address
However if it doesn't have a match it will want to send it towards it defined default nexthop and to do that it may need to initiate arp request whilst buffering the packet.
Upon receiving an arp reply the router will now have the destination mac address of its default nexhop so it will create a new L2 frame and encapsulate the packet and send it on its merry way, where again the process begins all over again.
Alternatively....
if the router sees that in the IP header the host dst address is a connected interface, it may not know the mac address of that host so it will initiate an arp request for the hosts mac-address whilst buffering the datagram(packet)
The host will see this arp request frame, then reads it and realises it has the ip address and then initiates an arp reply via unicast response.
Note: whilst this is all occurring the switch interconnecting the router and the host will be recording the mac- address of the router and host and what ports they reside on
The router now has the destination mac address of the host so it will recreate the L2 frame encapsulate the packet and send it to the host via the switch.
The host will then:
check the L2 header, sees that its for itself and strips it off
check the L3 header sees that its for itself and strips it off
check dst port and proceeds to process the data.
res
Paul
Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.
Kind Regards
Paul
