Odd LAN IP addressing...

humaxf1

Hi all,

This might be a silly question, but I'll ask it anyway. Is there any particular reason why a sbs server 2003/workstation network would have a 195.44.*.* address scheme (set as statics) for the local LAN. Internet is provided by Irish Broadband Breeze going into a D-Link router.

Just seems a bit odd to me. You would naturally expect to see a 192.168.x.x, 172.*.x.x or a 10.x.x.x. Are there any consequences having a 195.x.*.* scheme on a LAN?

TIA

DeadEight

Well one good reason would be if you owned/were assigned those addresses from your ISP for that purpose. It looks like the addresses are owned by C+W, but I could be wrong.

Those addresses are not private. Visit somethign like www.whatsmyip.net. Does the public and the LAN address match?

humaxf1

doing a whatismyip returns the IBB 87.*.*.* address.

I have attached the ethernet setup page.

daffy_duc

There's nothing stopping a person from using whatever IP range they want internally.
Its bad practice, and will only cause problems in the long run, but its will still work. For various values of "work".

RFC1918 addresses (192.168.0.0/24, 172.16.0.0/12 and 10.0.0.0/8) were set aside for this purpose though.

Lets imagine I've setup an office with internal IPs of 195.22.33.0/24
What happens when I try access an external website on 195.22.33.20?
The office PC, and the office Router, will think that the website is internal, when its not.

Thats why the RFC1918 addresses were set aside for this, because there will _never_ be a globally routeable host with an IP from that range.

Also, by looking at that configuration, it looks like you may still have some really really old IBB addresses configured on your router.
Irish Broadband stopped using those addresses many years ago, so I assume you've had that IBB Breeze connection for some time, and didn't quite get around to changing it properly?

Moriarty

It's a bloody terrible idea, but more common than you'd imagine unfortunately.

bushy...

Could be a really bad idea -- see PM

johnmacward

Any particular reason it would have been done like this in the past? I mean I doubt it was just some rookie who didn't know what they we're at and thought any numbers could be used, although thats also not impossible.

BigEejit

daffy_duc wrote: »

Lets imagine I've setup an office with internal IPs of 195.22.33.0/24
What happens when I try access an external website on 195.22.33.20?
The office PC, and the office Router, will think that the website is internal, when its not.

Thats why the RFC1918 addresses were set aside for this, because there will _never_ be a globally routeable host with an IP from that range.

This is the reason you should only use the 192.168.etc.etc addresses.

I once had a DNS problem with my broadband and rang up the helpdesk and the bangalore based gentleman went down through the various questions and one of them was "what is your internal ip range?" and I said it was 10.x.x.x and obviously that answer was not on the screen in front of the guy and he would not continue down the fault finding guide until I said I had changed it.

So if someone asks you that in future, just say its 192.168.xyz.xyz even if you are using 10.x or 172.x

johnmacward

Well in this case you're forced to use it / lie about it due to pure ignorance, thats stupid. I hate the 192.168.X.X range (well hate is too strong), I much prefer 10.X.X.X due too its ease of typing out.

JonathanAnon

Like was said above the only problem will arrive if you have to get to a website that is using the same public IP range that you are using for your private local network. In this case the packets will be routed locally and will not be passed through the router (as the host will be considered as being on the LAN).