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Router Conflict?

Last response: in Wireless Networking
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March 26, 2010 7:42:12 PM

Studying for A+ and have a general question. If two neighbors purchase the same exact router (linksys) and the factory IP is exactly the same (192.1.168.1) could this cause a problem when connecting where your PC could mistakenly use your neighbors router for general surfing? Even if you created unique SSIDs?

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Anonymous
March 26, 2010 8:04:34 PM

The IP address isn't really relevant.

You wouldn't connect by mistake even if the id was left at factory default (say Linksys or Netgear) if you already created a connection to your own router (and saved it as a profile in Windows or you wireless adapter's utility).

I suspect, because the profile will have identified and saved the router's unique MAC id.

As long as a profile exists and your own router has a good signal, such a mistake is unlikely.

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March 26, 2010 8:13:47 PM

Makes sense...I suppose what could happen in theory is you could connect to the other persons router and configure it mistakenly if no passwords were set etc.. Correct??
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Anonymous
March 26, 2010 8:35:03 PM

Sure, if you had not set a profile and the other guy had no security and had left the router setup password at the default you could mistakenly meddle with his settings.

But even if you locked the guy out of the wireless he could always access via an ethernet cable and if you changed the user setup password, that can be reset to defaults by pressing the reset button.
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March 26, 2010 9:39:36 PM

The only thing that distinguishes one wireless AP from another (for the purposes of establishing a wireless connection) is the SSID, security type, and network key. The MAC address of the router is irrelevant as far as the client is concerned (of course, that doesn’t mean the router couldn’t reject a client MAC address using MAC filtering). If those three parameters match more than one wireless router, and the wireless protocol (a/b/g/n) is mutually compatible, then it's entirely possible your PC could connect to any one of them. That is in fact what makes wireless roaming possible. And when neighbors buying the same product leave them configured w/ their defaults, can result in UNINTENTIONAL wireless roaming! Of course, signal strength and range will play a part in determining the likelihood of that happening.
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Anonymous
March 27, 2010 8:37:35 AM

Worth knowing.
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March 29, 2010 5:42:18 PM

Ok...sounds good. Hope I can squeeze one more question in w/out starting a new thread. How is it possible millions of homes can have an IP like 192.168.1.1 for the default gateway? Does the router have a MAC to distinguish it from another router?

tx

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March 29, 2010 6:06:38 PM

http://en.wikipedia.org/wiki/Private_network

Some IP ranges are considered "private", not public. Addresses like 192.168.x.x and 10.x.x.x are intended ONLY for local network use, precisely so millions of homes and businesses can have their own local IP address space. However, those private addresses are not routable on the public IP space of the Internet. That’s why you need a NAT router. A NAT router is assigned a public IP on its WAN port and then maps the local IPs behind it (e.g., 192.168.1.x, including its own 192.168.1.1 IP address) to that public IP. If you didn’t have a NAT router, then everyone behind the router would need public IPs in order to communicate w/ other public IPs.

IOW, the designers of the Internet and TCP/IP were smart enough to realize that having both private and public IP spaces had many advantages. Some ppl/businesses might not even want to be on the public IP space, they may simply want to have local IP networks for internal use. And that’s perfectly fine and causes no conflicts w/ anyone else using the same private IP space. But once you want to have those two private IP networks communicate w/ each other, NOW you need NAT routers on each private network, each w/ its own pubic IP.

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March 30, 2010 7:32:53 PM

k - so in a home network is my linksys router the NAT router or is that done on the ISP side? If my home router does get a public IP how is that assigned as it must be unique.
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March 30, 2010 11:42:17 PM

Yes, your Linksys is a NAT router. It receives a public IP by making a DHCP request to the ISP, the exact same way your PC would make a DHCP request to the ISP if the router wasn’t there. But instead of your PC being assigned the public IP (and thus making it not shareable), the Linksys router assigns the public IP to its own WAN port, then uses NAT to map it to all the wired and wireless clients behind it using a *local* IP space (e.g., 192.168.1.x).

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