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Standard User rtcw
(learned) Tue 16-Jan-24 21:59:06
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Community Fibre, mystery second hop in my traceroute result?


[link to this post]
 
Hi everyone,

I got connected with Community Fibre recently. I've been tinkering around with it but nothing too major.

When I was setting up a TBB monitor for IPv6, it kept giving me a 100% packet loss. I used the IPv6 from the first hop as I would usually do with other internet connections.

After some investigation, it turns out that my packets leaves my home when it's at second hop, not first hop as expected.

1 1 ms 1 ms 1 ms Community*****.cust.communityfibre.co.uk [192.168.1.1]
2 3 ms 3 ms 4 ms 147.12.*.* (my public IP address)
3 4 ms 2 ms 3 ms lag-4.agg-rr1.eas.lon.network.as201838.net [94.247.87.190]
4 3 ms 4 ms 4 ms lag-3.edge-rr1.ld8.lon.network.as201838.net [94.247.87.253]


The problem is, I login into my router via 192.168.1.1 which is a Linksys router therefore I was under the assumption the router gets their own public IP address and that's where TBB monitor would be pinging. But the reality is that it's 100% packet loss if I try to ping the 1st hop.

I'm not sure what is the second hop? I tried to connect to it via browser and got the 'connection refused' message.

It doesn't help that the second hop usually increases latency considerably compared to the other hops down the line. If I can remove that, great.

Edited by rtcw (Tue 16-Jan-24 22:13:53)

Standard User AndyPandy
(fountain of knowledge) Wed 24-Jan-24 14:20:56
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Re: Community Fibre, mystery second hop in my traceroute res


[re: rtcw] [link to this post]
 
The first hop is your router, the second hop is your ISP's network. This is normal, unless you're running the trace form within the router's firmware somehow.

If the second hop is your public IP, then something is very wrong. It should be a router on your ISP's network.

Go here to see your public IP: https://whatismyipaddress.com/

Edit: Also, those are all IPv4 addresses.


Hey!Broadband 1Gb Fibre - Live BQM
Asus AC86U - Asuswrt Merlin

Edited by AndyPandy (Wed 24-Jan-24 14:23:49)

Standard User jpm
(fountain of knowledge) Wed 24-Jan-24 16:06:54
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Re: Community Fibre, mystery second hop in my traceroute res


[re: rtcw] [link to this post]
 
If you got connected recently and you are using Linksys hardware then you are on CGNAT, so you don't have a public IP address.


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Standard User rtcw
(learned) Thu 25-Jan-24 00:09:25
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Re: Community Fibre, mystery second hop in my traceroute res


[re: AndyPandy] [link to this post]
 
Strangely enough, I was never behind the CGNAT from the day I was connected. I checked with Community Fibre, they confirmed this and the tracert results above also confirms it (as it would have shown 10.xxx somewhere if I was behind the CGNAT.

Bash
1
23
45
67
89
1011
12
.
   1     2 ms     1 ms     1 ms  ****.cust.communityfibre.co.uk [192.168.1.1]
  2     3 ms     3 ms     3 ms  *.*.*.*  3     4 ms     3 ms     3 ms  lag-4.agg-rr1.eas.lon.network.as201838.net [94.247.87.190]
  4     3 ms     3 ms     3 ms  lag-3.edge-rr1.ld8.lon.network.as201838.net [94.247.87.253]  5     3 ms     3 ms     3 ms  xge-0-0-0-25.edge1.ld8.lon.network.as201838.net [94.247.87.55]
  6     3 ms     3 ms     3 ms  xge-0-0-0-5.edge1.thn.lon.network.as201838.net [94.247.87.3]  7     2 ms     3 ms     3 ms  72.14.203.26
  8     2 ms     3 ms     3 ms  192.178.97.181  9     5 ms     4 ms     4 ms  209.85.241.93
 10     3 ms     3 ms     2 ms  lhr25s26-in-f3.1e100.net [172.217.169.3]


That's me pinging google.co.uk using IPv4, and the second hop is definitely my public IPv4 address so I've censored it. It matches the one seen on https://whatismyipaddress.com/



In reply to a post by AndyPandy:
The first hop is your router, the second hop is your ISP's network. This is normal, unless you're running the trace form within the router's firmware somehow.

If the second hop is your public IP, then something is very wrong. It should be a router on your ISP's network.

Go here to see your public IP: https://whatismyipaddress.com/

Edit: Also, those are all IPv4 addresses.


My mistake, here's my IPv6 tracert result:

Bash
1
23
45
67
89
1011
1213
1415
16
.
   1     1 ms     1 ms     1 ms  ***
  2     3 ms     3 ms     2 ms  ***  3     3 ms     3 ms     3 ms  lag-4.agg-rr1.eas.lon.network.as201838.net [2a02:6b60:0:1:2::190]
  4     4 ms     3 ms     3 ms  lag-3.edge-rr1.ld8.lon.network.as201838.net [2a02:6b60:0:1:1::253]  5     *        *        *     Request timed out.
  6     5 ms     4 ms     4 ms  2a02:6b60:0:1:3::62  7     4 ms     3 ms     4 ms  2a00:1450:80e1::1
  8     *        5 ms     *     2001:4860:0:1::73c6  9    11 ms    20 ms    23 ms  2001:4860:0:1::7dc2
 10     5 ms     4 ms     4 ms  2001:4860::c:4002:aff5 11     4 ms     3 ms     3 ms  2001:4860::9:4001:45d3
 12     6 ms     5 ms     4 ms  2001:4860:0:1::7dbb 13     5 ms     5 ms     6 ms  2001:4860:0:1::41dd
 14     4 ms     4 ms     4 ms  lhr35s02-in-x03.1e100.net [2a00:1450:4009:80a::2003]


The public IPv6 address from https://whatismyipaddress.com doesn't match any of the IPv6 addresses above in the tracert result however it matches one of the 6 IPv6 addresses my network adapter was given by the router according to my PC settings. I assume it is my PC's public IPv6 address. This address is not pingable externally.

The first hop, I've censored as I'm not exactly sure what it is but it appears to be a private IPv6 address of my router. If I put this IPv6 address in my browser, it takes me to Linksys login page. This IP address is not pingable either.

The second hop, it is definitely the public IPv6 address of my router, so I've censored it. This IP address is pingable.

It would appear that Linksys router has a weird configuration of having both private and public IP addresses.
Standard User AndyPandy
(fountain of knowledge) Thu 25-Jan-24 09:51:51
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Re: Community Fibre, mystery second hop in my traceroute res


[re: rtcw] [link to this post]
 
That is bizarre.

Getting back to the issue at hand; is the router configured to respond to ICMP packets on the WAN side?


Hey!Broadband 1Gb Fibre - Live BQM
Asus AC86U - Asuswrt Merlin
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