What is IP53B?

IP53B is a way to block port 53 (also called UDP53^*1) in advance to prevent servers which are considered as open resolver and communication devices from being used as a springboard for attacks including DDoS^*2.
By blocking access from external networks to member’s IP address, it prevents the device being used as a springboard for DDoS attacks.

1. *1UDP53: Also referred to as port 53. A path for devices to contact the DNS server.
2. *2DDoS attack: It forcibly increases the traffic to overload the communication server and stops the service function.

What is Open Resolver?

Open resolver is a DNS cache server which accepts DNS recursive queries from the whole communication devices which are connected to the internet without limiting the access source. It may be attacked (DDoS) or used as a springboard of an attack.

How members are affected

Your connection to the internet and sending and receiving of email will not be affected.
If you are operating a DNS server and if it is released on the internet, please note that your server will not be able to accept queries from IP addresses since port 53 is blocked.

Affected services

• All internet connection services except for Asahi Net au Hikari

How to release Port 53

If you have a fixed IP address, you can make a request to release port 53.
Please enter the required items on the following online form and make a request.

• Technical Support Inquiries

• *If the DNS server or router you are using is an open resolver, port 53 cannot be released.
  Asahi Net will confirm that your server/router is not an open resolver.
• *Asahi Net does not give support for detailed settings of the server or router you are operating. Please refer to the respective manual, guidance, etc. on your own.