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No, it would make your browser try to go to that IP to pull the ad. When you have those addresses resolve to the loopback, what happens is your browser sends the queries for the ad to your computer, your computer of course doesn't have them and the ads are therefore not shown on the page. The reason that works is because you have hardwired the name resolution to your computer and the only thing that would happen if you chose something other than the loopback is you would go to whatever IP you chose looking for the ads rather than your own computer (which probably wouldn't be appreciated by those IP's).
/nebulus
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A slightly diffrent explanation for the loopback address (/subnet):
TCP/IP is basically just another IPC (Inter Process Communication) mechanism. This means that it allows two processes ("running programs") to exchange information between each other.
Using that point of view, there's absolutly nothing to say that two such process that want to exchange info can't be on the same machine, nor that that machine has to be connected to a network. As so, a machine not on a network most likely has no unique IP address assigned to it. So it makes sence to have an IP address that's a loopback to enable IPC communications (over TCP/IP) on the same machine.
Further more, there's acually more than one loopback address: 127.0.0.0 is acually a class A net (127.0.0.0/8 or 127.0.0.0 netmask 255.0.0.0). This gives you an almost limitless amount of IPC channels!
Ammo
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A slightly diffrent explanation for the loopback address (/subnet):
TCP/IP is basically just another IPC (Inter Process Communication) mechanism. This means that it allows two processes ("running programs") to exchange information between each other.
Using that point of view, there's absolutly nothing to say that two such process that want to exchange info can't be on the same machine, nor that that machine has to be connected to a network. As so, a machine not on a network most likely has no unique IP address assigned to it. So it makes sence to have an IP address that's a loopback to enable IPC communications (over TCP/IP) on the same machine.
Further more, there's acually more than one loopback address: 127.0.0.0 is acually a class A net (127.0.0.0/8 or 127.0.0.0 netmask 255.0.0.0). This gives you an almost limitless amount of IPC channels!
Ammo
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Loopback actually goes through its own "interface" - this is a virtual interface which can't talk to any other machines. It has the advantage of having a lower overhead of having to go via an ethernet or ppp interface (for example) and will work even if no other interfaces are configured.
Additionally on machines that have demand-dialling, applications can use loopback even when the dialling is down without any risk of triggering a dial-up.
Most OSs also provide other IPC mechanisms for local IPC which may be more efficient than say TCP over loopback (which still requires the IP packets to be assembled and disassembled with headers), but it's there for compatibility with apps which can also run over a real IP network.
On most OSs, sending a packet to your own (real, non-loopback) IP address won't actually cause it to go on to a physical medium (for example ethernet), but involves some processing by the various layers before it works this out. Loopback avoids this by having an interface which automatically recieves all (and only) packet it transmits.
Finally note that it's not just IP address 127.0.0.1, but 127.anything at all.
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Loopback actually goes through its own "interface" - this is a virtual interface which can't talk to any other machines. It has the advantage of having a lower overhead of having to go via an ethernet or ppp interface (for example) and will work even if no other interfaces are configured.
Additionally on machines that have demand-dialling, applications can use loopback even when the dialling is down without any risk of triggering a dial-up.
Most OSs also provide other IPC mechanisms for local IPC which may be more efficient than say TCP over loopback (which still requires the IP packets to be assembled and disassembled with headers), but it's there for compatibility with apps which can also run over a real IP network.
On most OSs, sending a packet to your own (real, non-loopback) IP address won't actually cause it to go on to a physical medium (for example ethernet), but involves some processing by the various layers before it works this out. Loopback avoids this by having an interface which automatically recieves all (and only) packet it transmits.
Finally note that it's not just IP address 127.0.0.1, but 127.anything at all.
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One thing I find useful is you can ping 127.0.0.1 to make sure that tcp/ip is installed correctly.
w00t 1000 post seems like just yester day I still had my newbie tag. Thanks to everyone for teaching me so much.
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One thing I find useful is you can ping 127.0.0.1 to make sure that tcp/ip is installed correctly.
w00t 1000 post seems like just yester day I still had my newbie tag. Thanks to everyone for teaching me so much.
