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I got a question about IP addresses

I

illusion88

Lifer
Say you got two people, on two different ISP's, and they happen to have the same IP addresss, what happens? Can they both be online at the same time? How do the two different ISP's find out that there is an IP sharing violation? I can understand if they where on the same ISP, but what about from different ones? Any answers?
 
Can't be possible can it? I'm not insulting your intelligence but they aren't just using a router and getting the same internal ips and thats what you are seeing. Contact the isps if you are in question.
 
Good question, I would like to know too.

But how would they have the same IP address? If it's same, then it was assigned to them by their ISP's DHCP server, which is only local. When they connect to the internet, they are probably going through the ISP's proxy server, and then the IP address will be different and unique
 
i dont think anyone can have the same IP.

dont quoe me on that though. i think there is a closed limit on possible IPs in the world, and thats why static IP is expensive.
 
Originally posted by: illusion88
Say you got two people, on two different ISP's, and they happen to have the same IP addresss, what happens? Can they both be online at the same time? How do the two different ISP's find out that there is an IP sharing violation? I can understand if they where on the same ISP, but what about from different ones? Any answers?
Click to expand...

all ISP are allocated a certain IP pool so the chance that they are going to give the same IP is minimal. Besides when they would give you the same IP, that doesn't mean that this IP is routed further on the ISP's backbone. Only the customer with the valid IP is going to have internet access because it's routed on the ISP's backbone. The other one can probably only ping to the default gateway (the first hop) because they are in the same subnet but not any further
 
Originally posted by: LongCoolMother
i dont think anyone can have the same IP.

dont quoe me on that though. i think there is a closed limit on possible IPs in the world, and thats why static IP is expensive.
Click to expand...
IPs are getting limited but it is mainly because so many have been snatched up and they are no longer available. I remember someone posting this in the networking forum.

 
Originally posted by: Nocturnal
Why can't they just create more IPs? It isn't like it'll cause inflation, right? LOL
Click to expand...

They cannot with the current system because an IP address is a fixed number of binary digits -- namely 32. However, a new IP addressing scheme was created and is slowly being implemented across the Internet: IPv6, with a whopping 128 bits for an IP address. This new scheme has more than enough available IP addresses to assign a unique address to every atom in the universe.
 
Originally posted by: GigaCluster
Originally posted by: Nocturnal
Why can't they just create more IPs? It isn't like it'll cause inflation, right? LOL
Click to expand...

They cannot with the current system because an IP address is a fixed number of binary digits -- namely 32. However, a new IP addressing scheme was created and is slowly being implemented across the Internet: IPv6, with a whopping 128 bits for an IP address. This new scheme has more than enough available IP addresses to assign a unique address to every atom in the universe.
Click to expand...

Imagine trying to remember that long IP address.
 
Originally posted by: TommyVercetti
Originally posted by: GigaCluster
Originally posted by: Nocturnal
Why can't they just create more IPs? It isn't like it'll cause inflation, right? LOL
Click to expand...

They cannot with the current system because an IP address is a fixed number of binary digits -- namely 32. However, a new IP addressing scheme was created and is slowly being implemented across the Internet: IPv6, with a whopping 128 bits for an IP address. This new scheme has more than enough available IP addresses to assign a unique address to every atom in the universe.
Click to expand...

Imagine trying to remember that long IP address.
Click to expand...
I can't remember even IPv4 addresses, and they expect me to work with IPv6? 😉
 
Originally posted by: hdeck
Originally posted by: spidey07
We do not have trouble with IP addresses. There is plenty.
Click to expand...

until 2010 when there will be none left
Click to expand...


not true

the wide acceptance of things like NAT have slowed down the need for IPv6 in the near future
 
Originally posted by: GigaCluster
Originally posted by: Nocturnal
Why can't they just create more IPs? It isn't like it'll cause inflation, right? LOL
Click to expand...

They cannot with the current system because an IP address is a fixed number of binary digits -- namely 32. However, a new IP addressing scheme was created and is slowly being implemented across the Internet: IPv6, with a whopping 128 bits for an IP address. This new scheme has more than enough available IP addresses to assign a unique address to every atom in the universe.
Click to expand...

since the united states was allocated 70% or so of the orgininal 32 bit addresses, I don't think we will be converting anytime soon. It's the other nations that are running out right now. IPv6 is backwards comatible anyway so it doesn't make that much of a difference I wouldn't think.
 
the ip address your friends is using wouldn't happen to be 192.168.101.x would it? or something similar. If so that is an internal Ip address therefore it wouldn't matter becasue the computer it is assigned to is behind a firewall. The true Ip address is would be assigned to your router.

But if you have a home network setup you know this and my asnwer to the question is moot. oh well.
 
No, they cannot be online at the same time. Only one of them will be able to access the internet.

This happens more often than you think.
When you have a pure DHCP network and everyone sets their clients to DHCP, everything works as designed.
The DHCP server will/should not assign the same IP to 2 different clients.

But when you have someone who thinks they're smart, who sets their IP statically to a valid and available IP, he'll be able to get online.
What he'll do is he'll check his IP which is currently set to dynamic, decides he wants to keep it so he changes it to static. When his lease runs out, it doesn't automatically renew because he's now set to static, so his IP is released back into the available pool of IP's.

Then you'll have another person on the same network who's renewing his IP and coincidentally gets the same IP as the guy who set it statically (since it's now available in the pool of IP's).
The static guy can get online because he's recognized the network already, while the innocent dynamic user, struggles for hours trying to get his PC online and finally gives up and calls for tech support only to realize his IP has been "stolen" 😛
 
You can have the same IP address but only the one with that has its entries in the routing tables will work correctly.
 
Originally posted by: psteng19
No, they cannot be online at the same time. Only one of them will be able to access the internet.

This happens more often than you think.
When you have a pure DHCP network and everyone sets their clients to DHCP, everything works as designed.
The DHCP server will/should not assign the same IP to 2 different clients.

But when you have someone who thinks they're smart, who sets their IP statically to a valid and available IP, he'll be able to get online.
What he'll do is he'll check his IP which is currently set to dynamic, decides he wants to keep it so he changes it to static. When his lease runs out, it doesn't automatically renew because he's now set to static, so his IP is released back into the available pool of IP's.

Then you'll have another person on the same network who's renewing his IP and coincidentally gets the same IP as the guy who set it statically (since it's now available in the pool of IP's).
The static guy can get online because he's recognized the network already, while the innocent dynamic user, struggles for hours trying to get his PC online and finally gives up and calls for tech support only to realize his IP has been "stolen" 😛
Click to expand...
Bingo!!!!!

That is basically what happened to me 2 years ago. I received my IP address and the next thing I know is I have intermittent internet access. I could only stay online for about 10 mins at a time. I called support and they couldn't figure out why I was having problems. They said it maybe their network and to wait 24hrs to see if it clears up. It didn't, so I pestered them again. This time they monitored my access for 20 mins and noticed something very strange. They said my modem would be on then off then on again.

They could ping my modem one minute and not the next. I was then immediately transfered to tier 2 support. They said it could be an IP conflict and to look for errors. I was using win2k at the time and I had to go through about a 2 meg log where I finally found the message. They said they needed the mac address of the other machine to fix the issue. So once I found it I had to wait for support to find the person and get into contact with them. This all took a total of 5 days to fix from start to finish. I got credited for those days with no problems at all.


 
Oh sorry, just read your post again and you said different ISP's.
Each ISP should have their own scope of IP's and if they conflict, routing problems will occur. You can still get online but you will experience intermittent problems when they cross.
 
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