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192.168x.x = internal IP# right? then how can this be:

T

THELAIR

Golden Member
I just did a tracerout to a mail server of mine, and the 3rd hop
came back as:

192.168.3.65

how can that be? How can any number like 192.168.x.x be "live" on the internet? I thought it was only for internal purposes? Same with 10.x.x.x ?

maybe im mistaken.... but i thought it was odd.
 
192.168.0.x is an internal networkID. It's a C-class networkID so the first 3 bytes make up the networkID and the last byte the hostID. So 192.168.3.x is a legit external IP-addy.

Laterz,

Dennet aka "Suzie Q".
 
Not quite Suzie Q. As defined by rfc1918 the entire range of Class C's from 192.168.0.0 - 192.168.255.255 are allocated for private internets.

RFC 1918
 
Is the 3rd hop the final one to your mail server, or does it pass through any additional boxes on the way there?

I just tried to ping 192.168.3.65, and as expected I received Reply from (another IP): Destination host unreachable. Another IP = my company's provider.

Can you ping the 192 number directly? Can anyone who's not connected to (doesn't have an IP assigned by) your ISP see the 192 box in their tracert's of your mail server?

Do you see where I'm going? 🙂


Edit: Just a shot in the dark, but maybe your ISP used the 192/NAT config as a poor man's firewall -- blocking everyone who isn't on your ISP from using the e-mail server as a relay or something. It's just a wild guess; I might be way off. Have you ever tried to send mail from a friend's house (one on a different ISP) using your ISP's e-mail server?
 
Well Damaged, look like I stand corrected 🙂. It doesn't make much sense IMHO, because now you can subnet it like any other class B networkID. Ah well, guess you learn something new every day.

Laterz,

Dennet aka "Suzie Q".
 
Dumb question: Does anyone know how tracert differs from ping in reporting whether or not an IP/hostname is live? Is it common to see numbers via tracert that you can't ping directly?
 
traceroute, or tracert for you windoze users, varies in it's design. I believe, and I may be incorrect here, that the windoze version actually uses ping to get those responses from intermediate hops. The UNIX version typically runs echo over a high udp port, like above 30000 usually. Something like that. I don't think I'm too far off on my explanation. I'll see if I can find the info and report back.
 


<< It doesn't make much sense IMHO, because now you can subnet it like any other class B networkID. >>



True. But only true of you have something that understands VLSMs. Remember these were first divied up when all we had were classful networks. No subnetting to the extent that we do today. That's why the private range for a Class A is 10.X.X.X, the Class B is 172.16.0.0 - 172.31.255.255, and your class Cs were the 192.168.0.0 - 192.168.255.255. It's because they fall within those classful boundries.

Yes, today it seems strange, but there's a method to that &quot;madness.&quot; 🙂
 
Most ISPs run private network addresses within their network. That is...the parts they actually own and manage. You received a reply from one of their internal router interfaces which is completely normal. It is an accepted practice to save address space, especially for network providers.

cheers!
spidey

 
spidey07: Thanks for the info. I figured the 192 number must've been passed/routed somehow rather than have been directly accessible.
 
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