Hi nanog mailing list, Keep in mind that I am not a practicing network engineer, although I do have interest and knowledge on networking topics. I do not work for Verizon. I subscribe to Verizon FiOS, but not Verizon Wireless or Verizon's enterprise services. The Tor "directory" server with the IPv4 address 86.59.21.38 has been blocked by Verizon's AS701 backbone for a few months now. AS701 provides Internet connectivity to Verizon FiOS and Wireless. The design of Tor is that even though anyone can set up a "relay", there are a few central directory servers which clients go to first to get a list of relay servers and build a circuit (which is a path of three relays to reach a destination). A more descriptive overview of Tor is available here: https://www.torproject.org/about/overview.html.en . While I can still access other Tor directory servers from Verizon FiOS as running Tor as a client or relay does not require every directory server be unblocked, blocking one of them could possibly mean breaking some part of the Internet for a Verizon customer. A traceroute to 86.59.21.38 from FiOS shows that I can get through verizon-gni.net which is Verizon's internal FiOS network, but not ALTER.NET, which is Verizon's UUNet backbone: neel@xb2:~ % traceroute 86.59.21.38 traceroute to 86.59.21.38 (86.59.21.38), 64 hops max, 40 byte packets 1 unknown (192.168.1.1) 1.128 ms 0.780 ms 0.613 ms 2 lo0-100.NYCMNY-VFTTP-401.verizon-gni.net (173.68.77.1) 1.001 ms 3.632 ms 0.900 ms 3 B3401.NYCMNY-LCR-22.verizon-gni.net (100.41.137.96) 2.291 ms B3401.NYCMNY-LCR-21.verizon-gni.net (100.41.137.94) 3.172 ms 4.046 ms 4 * * * 5 * * * 6 * * * 7 * * * 8 * * * 9 * * * ^C neel@xb2:~ % In a normal traceroute, I would see ALTER.NET on hop 5. Also, this filtering is not a subnet filtering. A traceroute to 86.59.21.1 works: neel@xb2:~ % traceroute 86.59.21.1 traceroute to 86.59.21.1 (86.59.21.1), 64 hops max, 40 byte packets 1 unknown (192.168.1.1) 0.863 ms 0.757 ms 0.579 ms 2 lo0-100.NYCMNY-VFTTP-401.verizon-gni.net (173.68.77.1) 1.010 ms 1.545 ms 1.034 ms 3 B3401.NYCMNY-LCR-22.verizon-gni.net (100.41.137.96) 3.616 ms B3401.NYCMNY-LCR-21.verizon-gni.net (100.41.137.94) 5.696 ms 10.062 ms 4 * * * 5 0.et-5-1-5.BR3.NYC4.ALTER.NET (140.222.2.127) 3.492 ms 3.506 ms 2.996 ms 6 204.255.168.118 (204.255.168.118) 8.462 ms 7.479 ms 7.252 ms 7 144.232.4.84 (144.232.4.84) 5.041 ms 4.688 ms sl-crs3-lon-0-6-3-0.sprintlink.net (144.232.9.165) 71.865 ms 8 sl-crs2-lon-0-0-3-0.sprintlink.net (213.206.128.181) 72.214 ms 73.579 ms 72.339 ms 9 213.206.129.142 (213.206.129.142) 81.390 ms sl-crs4-ams-0-7-0-3.sprintlink.net (213.206.129.139) 85.854 ms 93.238 ms 10 217.149.47.46 (217.149.47.46) 79.004 ms 85.669 ms 79.392 ms 11 ams5-core-1.bundle-ether1.tele2.net (130.244.82.54) 86.507 ms 78.374 ms 77.740 ms 12 ams-core-2.bundle-ether9.tele2.net (130.244.82.57) 79.642 ms 77.926 ms 81.515 ms 13 wen3-core-2.bundle-ether15.tele2.net (130.244.71.47) 105.400 ms 105.089 ms 109.751 ms 14 tele2at-bundle2-vie3.net.uta.at (212.152.189.65) 122.716 ms 110.820 ms 114.354 ms 15 86.59.21.1 (86.59.21.1) 106.389 ms * 105.379 ms neel@xb2:~ % I had posted this finding on Tor's mailing list (https://lists.torproject.org/pipermail/tor-relays/2018-May/015218.html). I am posting here as (I believe) Verizon NOC people are more likely to read NANOG mailing lists than Tor mailing lists, although this post is modified from the original because not all network engineers may know how Tor works. From Tor developer Roger Dingledine (at the Tor mailing list), the reason why Verizon blocked 86.59.21.38 in the first place is probably the WannaCry ransomware, and the VZ NOC didn't realize it was a Tor IP address (or how Tor works), and then whoever did this block forgot about it and moved on. I can understand that you all may not know how Tor works either, so I included an overview link above. It could also be possible that it's the NN repeal (but less likely since it is on the level of UUNET not FiOS). I also contacted the operator of 86.59.21.38 as well as Verizon FiOS support, and neither were of much help (the former is obvious as he's Austrian). Well, thank you for reading. Best, Neel Chauhan === https://www.neelc.org/