Are we using Carrier Grade NAT now?

[#1]

Just noticed my gateway address is:

172.16.15.174

So a 20bit private network.

So does this mean that plus.net is doing NAT in its network? When did this happen? Have I just been slow in noticing?

[#2]

Moderator's note:
Thread moved from Broadband to Everything Else 

[#3]

Just noticed my gateway address is:

172.16.15.174

@summers Gateway addresses have always been non-routable.  It doesn't mean that CGNAT is being used, and it isn't!.

[#4]

Ah yes I see, my ip 51.7.13.47 is routable, but it goes via a gateway that isn't routable! Never noticed that before.

[#5]

AIUI you have a direct PPP connection to the gateway, all outbound traffic goes directly down the PPP tunnel and so its (the gateway) address is never used as an outbound route. Inbound traffic is routed to your gateway (since its routable on the private PN/BT network) and then directly back to you down the PPP tunnel.

[#6]

I see, yes my route has a default route to the gateway, so knows how to route that independent of it being public or private.

Then yes I guess on the otherside BT/Plusnet know that to route to my machine, they send it via a private ip address, that is known to BT/plusnet.

So yes it works, just interesting that the gateway isn't and can't be known about; out in the the general internet.

So makes me wonder what a traceroute gives from outside, as the traceroute to the gateway has to fail.

[#7]

If you are interested you can perform a traceroute to your router using either of these links, you'll need your broadband/public IP Address

https://dnschecker.org/online-traceroute.php or https://www.thinkbroadband.com/tools/traceroute 

Important the router needs ping (ICMP) replies enabled, for a Hub Two look in

Home >Advanced settings >Firewall >Configuration >Incoming ping - make YES

[#8]

Interesting the online one:

---

tart: 2024-06-27T21:22:19+0500
HOST: DNSChecker.org                                             Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- ???                                                        100.0     3    0.0   0.0   0.0   0.0   0.0
  2.|-- 10.74.11.36                                                 0.0%     3    0.4   0.7   0.4   1.1   0.4
  3.|-- ???                                                        100.0     3    0.0   0.0   0.0   0.0   0.0
  4.|-- 143.244.192.172                                             0.0%     3    0.3   0.5   0.3   0.7   0.2
  5.|-- 143.244.225.216                                             0.0%     3    0.8   0.9   0.8   1.0   0.1
  6.|-- 143.244.225.143                                             0.0%     3    0.8   0.8   0.7   1.0   0.1
  7.|-- NYIIX-gig1-0.ukcore.bt.net (198.32.160.80)                  0.0%     3    1.1   3.2   1.0   7.7   3.9
  8.|-- ixp1-ae-4.us-ash.gia.bt.net (166.49.195.133)                0.0%     3    6.0   6.2   6.0   6.5   0.2
  9.|-- t2c3-xe-7-1-0-2.uk-lof.gia.bt.net (166.49.195.140)          0.0%     3   79.4  81.8  79.4  86.2   3.8
 10.|-- t2c4-et-3-0-2-1.uk-lof.gia.bt.net (166.49.250.53)           0.0%     3   79.4  79.5  79.4  79.5   0.1
 11.|-- 166-49-209-195.gia.bt.net (166.49.209.195)                  0.0%     3   79.7  79.6  79.5  79.7   0.1
 12.|-- core2-hu0-15-0-4.southbank.ukcore.bt.net (109.159.252.143)  0.0%     3   79.8  80.0  79.8  80.3   0.3
 13.|-- ???                                                        100.0     3    0.0   0.0   0.0   0.0   0.0
 14.|-- ???                                                        100.0     3    0.0   0.0   0.0   0.0   0.0
 15.|-- 47.13.7.51.dyn.plus.net (51.7.13.47)                       66.7%     3  108.1 108.1 108.1 108.1   0.0

---

vs one on the router

---

traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 46 byte packets
 1  *  *  *
 2  *  *  *
 3  136.hiper04.sheff.dial.plus.net.uk (195.166.143.136)  27.440 ms  27.688 ms  27.561 ms
 4  peer3-et7-0-2.slough.ukcore.bt.net (194.72.16.68)  32.161 ms  peer2-et3-1-2.slough.ukcore.bt.net (194.72.16.212)  27.767 ms  27.664 ms
 5  109.159.253.235 (109.159.253.235)  26.863 ms  109.159.253.237 (109.159.253.237)  29.946 ms  109.159.253.189 (109.159.253.189)  27.046 ms
 6  192.178.97.49 (192.178.97.49)  29.240 ms  *  *
 7  dns.google (8.8.8.8)  27.397 ms  142.250.215.125 (142.250.215.125)  29.077 ms  dns.google (8.8.8.8)  28.088 ms

---

So yes the two routers closes to me don't give a reply, which is that have private IP  number makes their IP routing hard (unless they do NAT). So that could explain the *** ; rather than the machines just not responding to traceroutes.

It still amuses me that after a few hops inside plus.net it flips onto the main bt core network

[#9]

Here's mtr (my trace route) from me to you, I have a static public IP Address so my route is slightly different

mtr -w -z 51.7.13.47
Start: 2024-06-27T17:53:57+0100
HOST: wireguard                        Loss%   Snt   Last   Avg  Best  Wrst StDev
  1. AS???    192.168.10.1              0.0%    10    4.2   4.5   4.1   5.4   0.5
  2. AS6871   254.core.plus.net         0.0%    10   10.8  11.0  10.7  11.7   0.3
  3. AS6871   84.93.253.119             0.0%    10   11.5  12.0  11.3  13.7   0.8
  4. AS2856   195.99.125.138            0.0%    10   11.7  11.9  11.2  14.3   1.0
  5. AS???                          100.0    10    0.0   0.0   0.0   0.0   0.0
  6. AS???                          100.0    10    0.0   0.0   0.0   0.0   0.0
  7. AS6871   47.13.7.51.dyn.plus.net   0.0%    10   38.0  38.1  36.6  41.1   1.5
traceroute * * * usually means the device does not respond to ping

windows tracert reports

tracert 51.7.13.47
Tracing route to 47.13.7.51.dyn.plus.net [51.7.13.47]
over a maximum of 30 hops:
  1     1 ms     1 ms     1 ms  192.168.10.1
  2     9 ms     8 ms     9 ms  254.core.plus.net [195.166.130.254]
  3     9 ms     9 ms     9 ms  84.93.253.119
  4     9 ms    13 ms     9 ms  195.99.125.138
  5     *        *        *     Request timed out.
  6     *        *        *     Request timed out.
  7    36 ms    38 ms    36 ms  47.13.7.51.dyn.plus.net [51.7.13.47]