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I'm exampling Google's IPs, but you get the idea.

What happens if somebody configures a router's LAN address pool to range from 62.231.75.2 to 62.231.75.255, then his computer's IP address to 62.231.75.232 and someone else on the network tries to access Google?

Or better off, is there any case in which someone in that network can, by merely attempting to access Google, accidentally bump into another computer on the network?

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why down-votes? –  pQd Jun 25 '12 at 16:35

2 Answers 2

up vote 5 down vote accepted

computers in lan with such misconfigured router will be unable to access 'real' servers from that [ 62.231.75.0/24 ] range. computers in lan will 'think' that all machines from 62.231.75.0/24 network are reachable locally so instead of communicating via router and uplink ISP they will use ARP protocol to resolve IP addresses into MAC addresses; if they succeed they'll try to communicate with local machines [that will probably not listen on HTTP port, or if they listen they surely will not provide google services] or more probably there'll be no machine with requested address and connections will fail.

if we go deeper into it: google.com resolves into many addresses, possibly from different networks which can cause intermittent connectivity problems - once google.com will work, at other time - not.

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Yes i believe youd be right. It would just be LAN access. It would be like if Google IP was 192.168.1.27 and you changed your LAN ip setup to 192.168.1.0/24 and someone on that lan received a DNS response pointing to 192.168.1.27 your going to go to the local recourse since its in the same subnet.

nothing will happen though unless your running proxy services of web services.

Note: never user the 67 ips for local lans though and no public servers use 192.168. Its called public verse private addresses..just Google for the ranges/

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192.168.x.x - that's fine for private networks, but just 192 - that's very dangerous, check out how many dns root servers have 192 addresses en.wikipedia.org/wiki/Root_name_server –  pQd Jun 24 '12 at 18:43
    
sorry i ment in reference to 192.168.1.0/24 LAN im aware of the difference which is why i mention the public private ips have ranges. –  Graham.Fraser Jun 24 '12 at 18:56

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