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Thursday, August 16, 2012

How does an IP Packet prevent looping!

IP Packet contains a field called TTL – (Time To Live) in the header. Assume that computer 1 on a network pings computer 2 on another network. The networks are separated by a router. When the pings packet exits computer 1, the default TTL value is set by the operating system (128, 64 etc). When the IP Packet crosses the router, the router would decrement the TTL value by 1 and forward it to computer 2. Routers or Layer 3 devices would decrement the value of TTL by 1 every time an IP Packet passes through it, and ultimately when the TTL value reaches 0, the router which is in possession of the packet would drop it.

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