How does traceroute map the route a packet travels from point A to point B?
A.
Uses a TCP timestamp packet that will elicit a time exceeded in transit message
B.
Manipulates the value of the time to live (TTL) within packet to elicit a time exceeded in transit
message
C.
Uses a protocol that will be rejected by gateways on its way to the destination
D.
Manipulates the flags within packets to force gateways into generating error messages
Explanation:
Traceroute works by increasing the “time-to-live” value of each successive batch of packets sent.
The first three packets have a time-to-live (TTL) value of one (implying that they make a single
hop). The next three packets have a TTL value of 2,and so on. When a packet passes through a
host,normally the host decrements the TTL value by one,and forwards the packet to the next host.
When a packet with a TTL of one reaches a host,the host discards the packet and sends an ICMP
time exceeded (type 11) packet to the sender. The traceroute utility uses these returning packets
to produce a list of hosts that the packets have traversed en route to the destination.
C is the right Ans.
Ans: B
Traceroute changes the TTL on each set of 3 packets. After a hop (router) gets the packet it decreases the TTL value by 1 before passing it on to the destination. If TTL is 0 a Type 11 Code 0 is returned to the tracert originator. If the destination isn’t reached TTL is increased by 1 and process starts again.