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IP Addresses

Discussion in 'The Pub' at netrider.net.au started by pvda, Mar 9, 2006.

  1. I know we all have IP addresses when we log on.

    I thought if I log in at work being on a Permanent Network my IP addy would be the same all the time but I was led to believe if I'm using my home dial up account my IP changes depending on which connection my phone call enters the ISP's system through.

    The reason for asking this is a post in another thread in which a mod has linked three users to a common IP address (possibly hinting the users should be user) so I was just wondering if I'm right, wrong, half right, half wrong or just plain silly?

    I even put this in the Off Topic section as it aint bike related.
  2. Are you aware that there are a minimum of 12 people posting from your IP address? :shock: but I know quite a few of them and can vouch that they aren't all one and the same ;)
  3. There are
    Static:These get assigned to your ISP account and do not change each time you log on. You are stuck with it. This is good for servers where you need to know it's address all the time but _bad_ in other ways such as security.

    Dynamic: This changes "each" time you log in, your ISP has a certain range of addresses and they give you whatever address is free at the time. This means you can't predict what ip address you are going to have. Good for security etc.. but bad if you want to access your computer over the internet. To do that then you would run a dynamic update client like from no-ip.com

    Forgot to add (Incase you can't put two and two together) that your home dialup has a dynamic ip and your work most probably has a static ip.
    That is usually the case, of course a buisness doesnt need a static and a home user doesnt need a dynamic but that is usually how it is. One is more suited than the other to the different situations.
  4.  Top
  5. Moreover, if your ISP's security is good, the visible IP number will be the outermost gateway on their network, not the dynamically allocated address handed out to you each time you dial up.

    So, if three users all have the same externally visible IP number, this may simply mean that they connect through the same ISP - not that they are at the same computer.
  6. I've always said I'm as good as 10 men so maybe I'm as good as 12 :LOL:

    Thanks for the info......
  7. You beat me to it undii .... lol
  8. Ummm - it depends on your networks configuration, it is normal for every node (dynamic or static) behind your perimeter network devices to appear to all external as a single IP.

    So if you are connected to your ISP then things like forums will think you are the IP that is used by your ISps network.

    IPs should NOT be made public and i think its not only dumb but very irresponsible of admin to be posting them - it casts dispersion on their ability to maintain our privacy as their users. Do all of the mods have access to this info?
  9. Good for security bad for usability. I stab ISP's that use a supposedly transparent proxy that really isn't transparent so anything that requires direct client to client stuff has a cry. I don't particularly care if they run an anonymous proxy but tell me BEFORE i sign up.
  10. At work you will have 'dynamic' IP address assignment. When turned on, a PC will ask a server to give it an IP address, telling it it's unique ID for it's network card. That server will often issue the same/previous IP address, but may issue a different one to you PC instead for a couple of reasons.

    At home, the same situation works for most broadband users. For dialup users, they will in almost all cases, be given a different IP address from the ISP each time they dial-up.

    At work, your case is a special one though like many work environments. Your work browser/system is configured to access the internet through a work cache server. It is this cache server that connects to the Netrider server to get the page/content you want and return it back to your browser. That is why many people will show-up (as Flipper said) as coming from the same IP address. These people all work at your employer and have their systems configured to go through the same cache server.

    Most/All ISP's also run these cache servers too, and your web traffic (be you on dialup or broadband) is also going through one of these cache servers.

    Most of these cache servers will still report your PC's IP address to the Netrider server. A few, like the one you go through at your work, does not and only identifies the cache servers IP address to the Netrider server.
  11. Does that mean there are 11 other netriders working in your building that are running off the same IP address?
  12. Thanx for that Mouth, Next time I will wait a few more minnies for the answer ;)
  13. Ahh yes, the brutish hack we call NAT. If only we had some forethought, although i guess nobody was to know the internet would flourish so much.
  14. It's technically PAT or NAPT. Straight NAT is purely one-to-one address translation, whereas PAT or NAPT use varying port numbers to support multiple hosts being translated through a single IP. That threw me for a while with Cisco describing it in different terms to what I was expecting. :roll:

    Still, it's another "security" feature isn't it? :p
  15. :shock: out of curiosity i looked up my ip on here... 7 people posting from the same address and some ive never heard of before... could it be that tehy are with the same ISP as us? (dynamic ip addys)
  16. Yours is a special case again, but essentially the answer is yes.
  17. Well yeah i was using the term generally. It is acceptable to say NAT for any of those technologys untill you get down to more detail. But for general discussion....

    It was never really made for security it just pans out that way because we ran out of ip addresses. But yes it is good for security.

    I talk such crap sometimes... just ignore me :p

  18. yes and you are in IT? :wink:
  19. hey, mouth did say i am special ;)

    Im on my lunch break - I dont think IT stuff when im on a break :p
  20. Strange, the RFC seems to say it's multi addresses for NAT http://www.ietf.org/rfc/rfc3022.txt