As im still learning on this IP addressing stuff on dedicated servers permenantly connected to the internet, I just have a question.

I manage a network of computers, when I add a new computer to the network I assign it an address from the available pool this is fairly simple on corporate networks.

My question, which is realetd to PUBLIC IP addressing (or should i say, confusion) is, why would you have to wait for routers to update to notice an IP address on a network?
I know they have to update their routing tables etc... but how often is this done? and can an update be run manually?

Ive always been confused about this and would be really grateful if someone could enlighten me, lol

Depending on how your ISP has your service setup they may need to update the ARP Cache on the router (on a Cisco router this is done every 4 hours by default, or can be done manually by typing "clear arp").

The address resolution protocol (ARP) is a map of IP Addresses to MAC addresses of servers, switches, etc. This table is built automatically by the router, but, depending how the network is designed, it may mean that you cannot just add IP addresses to servers and have them respond right away.

There are generally two ways to get a server in that situation to respond faster:

1. As mentioned, type the command clear arp on the router.

2. Ping out from the server...when you do that you announce the server's MAC address and the router should pick it up.

Hope this helps.

so i suppose from that kind of information, the most anybody should have to wait to get a new IP address to be recognised across the internet is about 4-5 hours ?

Well, that would be true if the upstream provider used the defaulted 4 hour time frame. But some providers use a 24 hour cycle while some use a 1 hour cycle. It all depends on how and who is updating the routers.

Just to make sure: you are not talking about DNS propagation, correct? If you are not, then yes, it shouldn't take more than 4-5 hours for a router to start announcing a new IP address on its network.

Although, getting recongnized accross the Internet is slightly different. Routers route in the biggest chunks they can. So, if you have a server in New York and you care in California, the router you are connected to, does not ever recognize the specific address you are trying to get to (unless you have a VPN over frame or something), the router only knows that for this particular netblock (which may be all IP addresses) it is supposed to go to the next router in its sequence. Your router in California is going to only see the big pircture, ditto if you were sitting 2 blocks down from your server running over a cable modem. No one part of the Internet is going to recognize your server any faster than the other parts. It all relies on the router your server is connected to :D.

Of course Netblocks and DNS are different stories :D.

OK, that has cleared up alot of reserach, ive been wondering about that for a considerable amount of time :)

on a different topic, With DNS, i presume it has to propagate throughout the internet, therefore different parts of the internet will find the DNS address at varying moments. depending on where they are in the world.

and now going back to IP addressing as opposed to DNS:

Although as i see it, as long as the router in that particular netblock knows the IP address exists then the entire internet knows that address exsts. please tell me if i have the wrong idea, lol

I was also thinking along another point that uuallan mentioned earlier, that this IP address update is at the "Network Administrators Discretion" as in it doesnt have to wait the mandatory 1-24 hours to update?