What happens when a router receives a datagram?

• First it checks to see if the destination address is local (i.e. the router itself is the final destination)
• Next it decrements the Time To Live (TTL) field in the IP header. If it reaches zero, the datagram is discarded
• Finally it looks up the destination in a forwarding table to decide where to send it next
• Could be on a directly-connected network, or could have to send it via another router

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