Cosmit,
It works like this:
The TRACERT diagnostic utility determines the route to a destination by sending Internet Control Message Protocol (ICMP) echo packets to the destination. In these packets, TRACERT uses varying IP Time-To-Live (TTL) values. Because each router along the path is required to decrement the packet's TTL by at least 1 before forwarding the packet, the TTL is effectively a hop counter. When the TTL on a packet reaches zero (0), the router sends an ICMP "Time Exceeded" message back to the source computer.
TRACERT sends the first echo packet with a TTL of 1 and increments the TTL by 1 on each subsequent transmission, until the destination responds or until the maximum TTL is reached. The ICMP "Time Exceeded" messages that intermediate routers send back show the route. Note however that some routers silently drop packets that have expired TTLs, and these packets are invisible to TRACERT.
TRACERT prints out an ordered list of the intermediate routers that return ICMP "Time Exceeded" messages.
Example:
Tracert 10.1.1.0 "tracert sends an ICMP echo request with a TTL of 1"
1 10 ms 10 ms 10 ms 11.1.0.1
(1st router decrements the TTL of the packet to 0 and responds with a "Time Exceeded message", which tracert shows how long it took from the time it sent the message until it was received.)
"tracert sends another ICMP echo request with a TTL of 2"
2 71 ms 69 ms 72 ms 12.1.0.1
(1st router decrements theTTL of the packet to 1 and the next router decrements the TTL to 0 and responds with a "Time Exceeded message", which tracert shows how long it took from the time it sent the message until it was received.)
This continues until you reach your destination/routers silently drop packets with expired TTL (shows up as *************)/receive a destination unreachable.
Hope this helps
0bytes
