Security Basics mailing list archives
Re: 192.168.x.x oddities
From: JGrimshaw () ASAP com
Date: Tue, 15 Jun 2004 14:04:38 -0500
I once had a heck of a time connecting to a server of mine at home, which had the address 172.20.10.10. I could ping until I was blue in the face--it always came back. But I couldn't connect to the share, couldn't remote control it, nothing. The machine that I was on had a 192.168.1.x address, randomly assigned via DHCP (I have a few subnets for playing around in). When I went to the server to see if I could connect to a share on the client, I discovered the server was not even turned on! I did a trace route from the client and indeed, it went about 7 hops along inside my cable provider's network before coming to a halt--showing me a myriad of private networks on the way to the finish. So it is quite possible that your ISP has private networking enabled. Likely some of the addresses are what your cable modem/adsl modem receives it's TFTP connection from upon power up. "Jimmy Brokaw" <hedgie () hedgie com> 06/14/2004 04:48 PM Please respond to hedgie () hedgie com To security-basics () securityfocus com cc Subject 192.168.x.x oddities This seems like a stupid question from a non-guru like me, but I've asked a couple of the "gurus" I know and gotten nothing but strange looks. I run a small network at home, using a wireless router to connect to a cable modem. My internal IPs all fall in the 192.168.0.x range, which is the only address-space the router is configured to support. I've got authentication and logging, so before anyone says "I bet it's a neighbor using your connection," I've verified nobody else is logging in. My understanding is that the entire 192.168.x.x range is for internal networks only (RFC 1918), and unrouteable on the Internet. When I run the following command, however, I can see several computers: [computer]$ nmap 192.168.*.* -sP I get what looks like four computers (in addition to mine), plus some x.0 and x.255 addresses responding to the pings. I picked one at random, and it appears to belong to my ISP. Doing a traceroute, I found the packet reached its destination at a public (routeable) address, indicating to me the machine has two addresses on the same interface. RFC 1918 states: One might be tempted to have both public and private addresses on the same physical medium. While this is possible, there are pitfalls to such a design (note that the pitfalls have nothing to do with the use of private addresses, but are due to the presence of multiple IP subnets on a common Data Link subnetwork). We advise caution when proceeding in this area. Am I therefore correct in my assumption that the ISP is routing my pings onto their internal network? Is this a normal response? It seems like there ought to be security concerns here, but I can't nail them down, except the assumption that traffic destined for 192.168.x.x addresses may not be filtered as well (or at all), since it may be assumed it originated from within the internal network. -- \\\\\ hedgie () hedgie com \\\\\\\__o Bringing hedgehogs to the common folk since 1994. __\\\\\\\'/________________________________________________________ Visit http://www.hedgie.com for information on my latest book, "Waiting for War," published by Aventine Press! --------------------------------------------------------------------------- Ethical Hacking at the InfoSec Institute. Mention this ad and get $545 off any course! All of our class sizes are guaranteed to be 10 students or less to facilitate one-on-one interaction with one of our expert instructors. Attend a course taught by an expert instructor with years of in-the-field pen testing experience in our state of the art hacking lab. Master the skills of an Ethical Hacker to better assess the security of your organization. Visit us at: http://www.infosecinstitute.com/courses/ethical_hacking_training.html ---------------------------------------------------------------------------- --------------------------------------------------------------------------- Ethical Hacking at the InfoSec Institute. Mention this ad and get $545 off any course! All of our class sizes are guaranteed to be 10 students or less to facilitate one-on-one interaction with one of our expert instructors. Attend a course taught by an expert instructor with years of in-the-field pen testing experience in our state of the art hacking lab. Master the skills of an Ethical Hacker to better assess the security of your organization. Visit us at: http://www.infosecinstitute.com/courses/ethical_hacking_training.html ----------------------------------------------------------------------------
Current thread:
- 192.168.x.x oddities Jimmy Brokaw (Jun 15)
- Re: 192.168.x.x oddities JGrimshaw (Jun 16)
- RE: 192.168.x.x oddities Nathaniel Hall (Jun 16)
- Re: 192.168.x.x oddities Ranjeet Shetye (Jun 18)
- Re: 192.168.x.x oddities steve (Jun 21)
- RE: 192.168.x.x oddities Burton M. Strauss III (Jun 21)
- <Possible follow-ups>
- RE: 192.168.x.x oddities Shawn Jackson (Jun 16)
- RE: 192.168.x.x oddities Jimmy Brokaw (Jun 21)
- Re: 192.168.x.x oddities steve (Jun 23)
- RE: 192.168.x.x oddities David Gillett (Jun 24)
- RE: 192.168.x.x oddities Jimmy Brokaw (Jun 21)
- RE: 192.168.x.x oddities Mike (Jun 17)
- RE: 192.168.x.x oddities Shawn Jackson (Jun 17)