This blocking can help prevent your IP address being attacked from an external network and therefore also help prevent your server from being used as the springboard for a DDos attack. When a server or other communication device is being used as the platform for DDoS attacks ※1 Inbound Port 53 Blocking (IP53B) can be used to block port UDP53 ※2. This page is about the implementation of Inbound Port 53 Blocking (referred to as 'IP53B') and about how to request the removal of IP53B. FAQs about Managed Router for Small Businesses.High Speed Mobile (Xi-LTE & FOMA-3G Compatible) (Japanese).Neo-Discount ADSL(50M/12M) / Neo-Discount ADSL (IP Phone Available)(Japanese).FLET’S Hikari Next/ FLET’S Hikari Lite / B FLET’S / FLET’S Hikari Premium.Asahi Net Hikari (For the first time users of Fiber-Optic lines)(Japanese).Asahi Net Hikari (For FLET’S Users)(Japanese).For Mobile Devices - Unlimited Data Backup（AOS） (Japanese).