Quote:
Originally Posted by Peter N
A general request for the tech-experts (texperts?)
Can one of you post a laymans explanation of the use of traceroutes and how it relates to this issue? It may help some of the non-techys amongst us to understand the significance of all of these posts.
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Every packet you send out on the network has an associated TTL (Time to Live). This is typically set to 30 so that in the event of a routing loop that packets will eventually die off.
Every layer 3 (IP)device in the chain will decrement this TTL by one. If the packet should die, it is usual for the layer 3 device to send an error message to the orininating device.
In the case of traceroute, these tcp packets are sent with each packet incrementing it's ttl by 1.
So, first packet TTL=1
Second packet TTL=2
etc.
Traceroute can then compile a list of layer 3 hops by using the returning error message (which comes from an IP address). If there is a reverse-dns lookup available for that IP address it will also list it's name (not always configured).
If you get * * * as a response from a hop then it means that the device is prevented from sending error responses back to you. That also explains why traceroute can carry on because after it times-out 3 packets in succession it moves on to sending the next packet out with an extra +1 to the TTL (so the packet dies at the next hop).
Does that help?
EDIT
oh! just re-read your request for a laymans explanation...it's all done by magic (and pixies)