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Router IP addresses???

Posted on 2003-03-10
Medium Priority
Last Modified: 2010-03-19
Forgive another newbie question. I was refered to the website www.samspade.org in an earlier post, great site.  Anyway out of curiosity I entered my companies website address in the DO STUFF box, the tracert section return an 10.4.xx.xx address before getting our address.  This IP has a MAC address for a Linksys device.  At first I didn't catch that the 10.4.xx.xx (which is similiar to our internal static address) was between our ISP and our router.  So I used GFI LANguard to check that range of IP addresses, wondering if we had something undocumented on the network.  LAnguard returned tons of Cisco machines within this range.  Should 10.4.xx.xx be reserved and not used internally? any clarification would help.  maybe some easy points for someone
Question by:doie30286
LVL 79

Expert Comment

ID: 8106445
G'day, doie30286

Interesting. You should never see any 10.x.x.x addresses in the internet. See RFC 1918. I know that many ISP's use them internally, but NAT should give them all a public address for anything traversing the Internet.

Another great site (don't laugh) = Church of the Swimming Elephant http://www.cotse.com
And http://www.dnsreport.com  (plug in your domain)

LVL 24

Expert Comment

ID: 8106815
So who is it started trace?

Note, unit starting a trace typically begins on local intranet.
LVL 41

Expert Comment

ID: 8107073
>Should 10.4.xx.xx be reserved and not used internally?
it should only be used internally
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Accepted Solution

TheAmigo earned 500 total points
ID: 8107211
Would you mind posting a copy of the traceroute section from the bottom of the page.

My initial guess is that the 10.x.x.x addresses are used between routers at your ISP.  Doing a traceroute is the only time they show up... normally, the router won't send you any packets, but when doing a traceroute, it lets you know it dropped a packet so you get to see it's address as the source.  This is a fairly normal occurrance and nothing to worry about.

Do the IPs after the 10.x.x.x look more normal?

Expert Comment

ID: 8107232
As an example, putting www.netscape.com into Sam Spade's traceroute tool, has this at the end:

10   75.169 ms  pop2-mtc-P2-0.atdn.net (DNS error) [AS1668] AOL Transit Data Network
11   75.109 ms  ow2-mc3.atdn.net (DNS error) [AS1668] AOL Transit Data Network
12    77.139 ms  DNS error
13    77.066 ms  main-v1.netscape.aol.com (DNS error) [AS1668] AOL Transit Data Network

Note that 172.20.x.x falls in the same private IP category as 10.x.x.x (RFC 1918).  This isn't a problem, just means that they're using private IPs between routers rather than waste real IPs when they aren't needed.
LVL 51

Expert Comment

ID: 8108226
It's very possible your ISP is providing you with private addressing to their network and NAT'ing from their internal network to the internet.

What you're seeing is likely devices they are using to segment their internal addressing.


Author Comment

ID: 8110769
here is a copy of the tracert from Samspade.org, the final hop (which I over looked at first) is correct.  Thanks for all the great input.  I think points will go to Amigo, my habits are to leave the question open for a few days just to get more input, which is what this site is all about.
Again, thanks to all.
Should I at least report this to our ISP?

 3    8.836 ms  
 4    14.734 ms  mae-la.above.net
 5   19.453 ms  pos3-
 6  16.298 ms  pos2-
 7  81.884 ms  so-5-1-
 8  80.631 ms  so-6-0-
 9   78.970 ms  pos2-
10    85.640 ms  
11       81.859 ms  p15-
12      80.717 ms  p14-
13      79.839 ms  g49.ba01.b000173-
14     82.602 ms  
15    77.344 ms  DNS error [AS6983] ITC
16    78.031 ms  pos8-0-DELTACOM
17       80.996 ms  DNS error
18      82.829 ms  DNS error [AS6983] ITC DELTACOM
LVL 79

Expert Comment

ID: 8110874
It looks like internal addressing within deltacom, only between their internal routers, which is very typical. The only times you could see this address is through a traceroute, simply because of the way traceroute works as opposed to a ping or other browsing. It has no effect on your Internet use even if your were 10.4.22.x on the inside of your network

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