private IP addresses in traceroute

[Justinh]

My computer is plugged into my pass-thru cable modem (so the PC has the WAN IP address). I did a traceroute to cnn.com and got:
10.180.x.x
172.30.x.x
10.16.x.x
10.16.x.x
10.16.x.x
68.66.x.x ...

It took (5) hops before it hit a WAN IP address. How can this be? The first (or second at most) should have been a WAN IP.

 

[ColinTaylor]

Quite normal. It's the routing through your ISP's internal network.

 

[tgl]

It's certainly legal for an ISP to set things up that way, but I concur with @Justinh that it seems like dubious practice. Each additional router hop adds a couple of milliseconds (typically) so this doesn't look like a high-performance setup.

As a comparison point, I use Verizon FiOS. Outgoing traceroute shows my router, then two Verizon machines (the first-level is always the same one, but second-level varies) and then we're out to major internet backbone relays such as alter.net:

 1  router1 (192.168.1.2)  0.365 ms  0.371 ms  0.400 ms
 2  lo0-100.PITBPA-VFTTP-320.verizon-gni.net (68.162.161.1)  2.944 ms  2.942 ms  2.914 ms
 3  B3320.PITBPA-LCR-22.verizon-gni.net (100.41.9.158)  4.665 ms B3320.PITBPA-LCR-21.verizon-gni.net (100.41.9.156)  4.415 ms B3320.PITBPA-LCR-22.verizon-gni.net (100.41.9.158)  6.778 ms
 4  200.lag-28.ASBNVAEG-PPR02-CC.ALTER.NET (140.222.14.75)  11.310 ms  13.226 ms  13.228 ms
 5  63.125.107.22 (63.125.107.22)  9.847 ms * *
 6  port-channel3.core2.xrs1.he.net (184.104.188.66)  11.574 ms  11.865 ms  11.847 ms
...

 

[Justinh]

Very much unexpected, but what do I know . My fiber ISP (that is thru my router) is like tgl's experience.