Tue Aug 10, 2010 7:26 pm
You mean a traceroute to 4.2.2.2 times out on transient hops but reaches the target? The hops the traceroute traverses don't respond to ICMP traceroutes.
When you traceroute to a target, the client first sends out an ICMP traceroute packet with a TTL of 1. The first router in the way receives it, decreases the TTL to 0 and reponds. The client then sends out another ICMP traceroute packet with a TTL of 2. The first router in the way receives it, decreases the TTL to 1 and forwards the packet to the next router. That next router decreases the TTL to 0 and responds. Your client does that until the target router responds, each time increasing the TTL by 1.
If a router in the way doesn't respond to the traceroute packet, the traceroute on that hop will time out. Your client will still send another packet with a higher TTL to investigate the next hop.
But I'm not sure I understood the question right.