What happens if... (internet/lan related)

Forums › LAN (ethernet/Wifi/routers/Bluetooth) › What happens if... (internet/lan related)

Aaroona

3204 posts

Uber Geek
+1 received by user: 169

#73086 8-Dec-2010 20:47

If you get an internet address that resolves to say 192.168.1.x and your internal network uses 192.168.1.x addresses.

so say www.google.com = 192.168.1.1, would that send me to my router if I clicked or tried to access that link?

If not, can someone please point me to the right place where I can read about it?

muppet

2642 posts

Uber Geek
+1 received by user: 1660

Trusted

#414767 8-Dec-2010 20:55

You'll never get that address given to you for a public website (at least at the moment!). 192.168 is reserved and never to be used on the public Internet.

The Internet routers I manage drop any traffic they see destined for that address. If one of our upstreams, peers or customers tried to teach us that as a route, we'd drop that announcement (i.e. we wouldn't learn it)

If it WAS to happen however, you'd never get to Google. Your computer would try and send the traffic locally, it'd never forward it to your router. It'd send out an ARP request instead asking for the 192.168.1.x address. Nothing would answer (or if there was something with that address, it wouldn't be running a web server probably)

Does that answer your question?

Sorry, I should clarify that if it was going to 192.168.1.1 and that was also your router's address, your router's webserver would reply. What it would reply with (because you're asking for google.com and not 192.168.1.1) I don't know, it depends how the webserver in the router's configured. Most likely, you'd get your standard router admin login page.
You can test this yourself. Put 192.168.1.1 in your hosts file in windows for google.com
Then visit google.com and see what happens!

If google's address was 192.168.1.10 though, you'd get nothing (unless you had a device on the network with .10 as an address that had a webserver)

Audiophiles are such twits! They buy such pointless stuff: Gold plated cables, $2000 power cords. Idiots.

OOOHHHH HYPERFIBRE!

russelljsmith

23 posts

Geek

#414768 8-Dec-2010 20:59

Hi,

Should never happen; while most IPs can be resolved to certain websites or devices attached to the internet there are ranges of IP Addresses are *reserved* for other functions.

192.168.xxx.xxx addresses for example are reserved for internal addressing on a network, hence you'll often find a router will issue IPs in this range.

Here's a list of reserved address ranges: http://en.wikipedia.org/wiki/Reserved_IP_addresses

Hope that helps / R.

Aaroona

3204 posts

Uber Geek
+1 received by user: 169

#414769 8-Dec-2010 21:00

Thanks for your reply. That's exactly like I had thought. my mate and I were having a discussion about it, and he assumed that it would be sent because google.com isnt in the host file as being 192.168.1.1, so the request would be sent to the ISP etc and it would get to google.

but anyways, that does answer my question, and confirms what I thought. He's sitting here feeling sheepish I think ;)

russelljsmith

23 posts

Geek

#414770 8-Dec-2010 21:01

Didn't mean to duplicate @muppet there, you beat me to it! ;-)

Aaroona

3204 posts

Uber Geek
+1 received by user: 169

#414771 8-Dec-2010 21:02

russelljsmith: Hi,

Should never happen; while most IPs can be resolved to certain websites or devices attached to the internet there are ranges of IP Addresses are *reserved* for other functions.

192.168.xxx.xxx addresses for example are reserved for internal addressing on a network, hence you'll often find a router will issue IPs in this range.

Here's a list of reserved address ranges: http://en.wikipedia.org/wiki/Reserved_IP_addresses

Hope that helps / R.

Thanks for you reply.

I was talking as though it were allowed;

and that 192.168.1.1 was google, and also my internal network as well.

But I think I've found my answer, which I was looking for.

Thanks for your replies.. I'm actually going to have a read of the reserved IP's as well, I wonder what others are there....

Cheers!

muppet

2642 posts

Uber Geek
+1 received by user: 1660

Trusted

#414772 8-Dec-2010 21:05

Any traffic for 192.168.1->192.168.1.254 will never leave your network.

Any traffic for any other address is sent to your default gateway, which for your PC will be your router (192.168.1.1)

It will then route that traffic out to the Internet.

If you were trying to access beer.com at 192.168.1.23 Your
PC will send out a ARP Request (who has 192.168.1.23 please?) to the local
LAN. No one will reply, so the traffic will be dropped.

Hope that helps your mate!

Cheers,
muppet

Audiophiles are such twits! They buy such pointless stuff: Gold plated cables, $2000 power cords. Idiots.

OOOHHHH HYPERFIBRE!

Samsung

Shop now on Samsung phones, tablets, TVs and more (affiliate link).

webwat

2036 posts

Uber Geek
+1 received by user: 145

Trusted

#414933 9-Dec-2010 11:23

Its actually the IP address and subnet mask that decides what traffic gets sent to the gateway ? if the destination is not on the local subnet then it gets sent to the gateway. The gateway of course knows that 192.168.1.x is the local subnet (LAN) and sends other traffic to the WAN, which could be another subnet like a DMZ or just going directly to your ISP.

If you setup your DNS or hosts file to resolve google to a LAN address then you could host a local google server, but once the name has been resolved to an IP address there is no need to ask the router to compare it with another DNS or resolve it again. Of course your fancy local google server would do its own searches to google for anything not locally cached.

Time to find a new industry!

muppet

2642 posts

Uber Geek
+1 received by user: 1660

Trusted

#414939 9-Dec-2010 11:35

Yes, I've made the assumption in my posts that it's a /24 mask in use - that's how most home jobbies routers are setup by default.

The whole 192.168.0.0/16 is marked as private though. For 10.0.0.0 it's a whole /8

http://www.faqs.org/rfcs/rfc1918.html

I don't understand your second paragraph at all webwat. Can you explain again? Are you talking about DNS caching?

Audiophiles are such twits! They buy such pointless stuff: Gold plated cables, $2000 power cords. Idiots.

OOOHHHH HYPERFIBRE!

Oldhat

180 posts

Master Geek

Lifetime subscriber

#415754 11-Dec-2010 01:49

Something very similar to your query in the post http://www.geekzone.co.nz/forums.asp?forumid=49&topicid=71740

Kraven's response gives you an idea of what can occur ( or more precisely, not ) with your type of scenario.