IT question.  Why can I route (ping/tracert) out of my subnet? - Page 1
Forum section: electronics / general

author: Smokey
author_rank: Super Contributor
timestamp: May 15, 2015, 03:59:27 am
content: I hate sounding like a noob, but I really don't know much about networking. If I was going to the doctor I'd start this conversation with "So I have this friend that has a problem .... Not me.. Right, my friend... So this friend...."Anyways... here we go...My network is now currently set up on 192.168.2.0. I've always used 192.168.1.0 before so when I went to ping my router just now, out of instinct I typed 192.168.1.1 which is nothing.... and to my surprise it worked even through I don't have any machines on 192.168.1.0 anymore. What the hell?Doing a tracert on 192.168.1.1 shows 8 hops starting with my router, through public internet addresses, to 192.168.1.1. Other addresses I'm not using like 192.168.3.1 also route successfully. I did an nmap scan and none of those addresses have any ports open or anything.Is this normal and I just never through to try pinging an address outside my subnet before? Why is my router even try to route that? Someone drop the networking knowledge on me.Router = DDWRTPC = Windows7

author: TSL
author_rank: Regular Contributor
timestamp: May 15, 2015, 04:27:08 am
content: Hi Smokey,Publishing your traceroute would go a long way to understanding where things are going weird.Its not entirely unusual to traceroute to these "private" addresses if your ISP uses them in the ADSL cloud one level up from your modem thus its possible to find a path inside the base network of the ISP but rarely outside of the ISP networks.THE ISP's routers generally have firewall rules/ACL's at their edge to prevent propagation of those routes out onto the internet.regardsTim

author: sleemanj
author_rank: Super Contributor
timestamp: May 15, 2015, 04:35:24 am
content: There's no reason your router would not attempt to route through it's default gateway for such addresses which are not on it's network and it does not otherwise know how to route and you have not blocked them from being routed.Typically ISP routers would drop the packets for those reserved private networks as they enter their network, obviously your's doesn't either by design (eg, maybe they use private addresses for a NAT setup) or oversight, and through some confluence of routing the packets that your router by default sent out of the network because it didn't have anywhere else to send them managed to get to an actual destination and back to you.

author: Smokey
author_rank: Super Contributor
timestamp: May 15, 2015, 05:01:11 am
content: Interesting. Thanks for the replies.My ISP is Time Warner Cable (TWC) internet. The tracerts do all appear to be inside TWC.Tracing route to 192.168.1.1 over a maximum of 30 hops1 <1 ms <1 ms <1 ms router [192.168.2.1]2 8 ms 9 ms 8 ms cpe-75-83-64-1.socal.res.rr.com [75.83.64.1]3 19 ms 7 ms 9 ms tge0-9-0-16.hwthca2802h.socal.rr.com [24.30.173.121]4 19 ms 27 ms 23 ms 72.129.33.1425 17 ms 19 ms 19 ms agg25.tustcaft01r.socal.rr.com [72.129.33.2]6 18 ms 19 ms 19 ms agg1.sndhcaax02r.socal.rr.com [72.129.1.3]7 33 ms 41 ms 32 ms agg1.sndhcahr02h.socal.rr.com [72.129.3.61]8 18 ms 15 ms 21 ms 192.168.1.1Trace complete.

author: ivaylo
author_rank: Frequent Contributor
timestamp: May 15, 2015, 05:52:50 am
content: Nothing to worry about. Some morron at your ISP configured a 192.168.1 subnet and their routers are finding it. Or could it be a catch all so such requests don't escape their network? In any case, you can safely use or not use this subnet for your own purposes.

author: Smokey
author_rank: Super Contributor
timestamp: May 15, 2015, 07:22:07 am
content: Cool. Do you think I should try to contact someone at the ISP?

author: BurtyB
author_rank: Regular Contributor
timestamp: May 15, 2015, 10:44:41 am
content: Quote from: Smokey on May 15, 2015, 07:22:07 amIf you can get to the right people via support I'm sure they are well aware of their RFC1918 address usage as they've been doing it for well over a decade.

author: ivaylo
author_rank: Frequent Contributor
timestamp: May 15, 2015, 02:48:55 pm
content: Quote from: Smokey on May 15, 2015, 07:22:07 amYou could try. If you are patient. The people who pick up the phone are probably in India and the first 100 questions you'll have to answer will be in the spirit of "sir, what version of Windows is your computer running?", "sir, is computer on or off?"...

author: Jeroen3
author_rank: Super Contributor
timestamp: May 15, 2015, 09:51:19 pm
content: If you router is setup as router, it will route the packet away from your network to the default gateway since it is supposed to do that with addresses not in the routing table.However, it is not desirable this way.Instead, you should configure your router as gateway, so that is refuses to route private ranges you're not using to the internet. Because now it is also capable of routing all sorts of internal traffic, such as automated discovery protocols of sorts, upnp and less encrypted local services to the isp's net.Did you check if there is any incoming traffic filtering? Or is it happily routing that as well? Which would be rather unsafe.