Route selection

ALL ROUTERS need not know all routes/paths in the internet..... the basic idea is next hop....each router needs to know the exact next hop or interface for a particular packet.....
consider a person travelling from new york to london. the taxi driver picks him up drops him at the NY airport.. the airlines drop him to london airport & the london taxi driver takes care of the destination ...... if we assume the entities as routers, the taxi router just knows how to reach the new york airport....the airline router knows how to reach the next hop i.e. london airport and so on.....................
So this internet hierarchy gives a complete transport mechanism for the internet..........

coming back to the ping question ..... the routers know the best next hop or interface to transfer the packet to reach the destination....so even if routers know of many paths(inturn interfaces) it always chooses the best next hop......

To intentionally oversimplify everything stated above(and add in some connections):

Route selection is Next hop
Next hop paths are evaluated based on Routing tables and default paths
Routing tables and default paths are populated by people based on the hierarchical nature of the IP addressing system.



The hierarchy was developed by people based on a large list of distance metrics and ip categorization.



Would this be an accurate assessment?

Yes, apart from the very last line which I had a little trouble understanding and which might be unnecessary anyway. Your preceeding statements explain the situation fully

coming back to the ping question ..... the routers know the best next hop or interface to transfer the packet to reach the destination....so even if routers know of many paths(inturn interfaces) it always chooses the best next hop......

But why it the maximum hop count is 16, why not upto 254??.

Large IP internetworks can have thousands of interconnected routers that pass datagrams between devices on various networks. In large internetworks, the topology of connections between routes can become complex, which makes routing more difficult. Routing protocols will normally allow routers to find the best routes between networks, but in some situations an inefficient route might be selected for a datagram.

In the worst case of inefficient routing, a router loop may occur. An example of this situation is where Router A thinks datagrams intended for network X should next go to Router B; Router B thinks they should go to Router C; and Router C thinks they need to go to Router A.
If a loop like this occurred, datagrams for network X entering this part of the internet would circle forever, chewing up bandwidth and eventually leading to the network being unusable. As insurance against this occurrence, each MAXIMUM HOP COUNT limitation
Maximum hop count is variable it can be increased or decreased....for RIP its 16 and for others it varies.....

Maximum hop count is variable it can be increased or decreased....for RIP its 16 and for others it varies.....

I think by mistake I have written ping in place of traceout and it has created a lot of confusion.
MY question is that whenever we trace a network, it shows max of 30 hops. And I have always found that it never increase to 16.
Why it shows a max of 16 hops only?????

Is traceout works on RIP protocol.???