Knowledgebase:
Advisory (2/23/2017) FRITZ!Box cannot be used for DNS resolution
Posted by Craig Gilmore, Last modified by Aly Essa on 24 February 2017 02:10 PM
Overview

According to the knowledge base article here, "A computer in the FRITZ!Box home network (192.168.178.29) cannot access a web server on the same home network because the DNS request for this web server (my_domain.de) is answered with an IP address in the same home network (192.168.178.20)."  


"For security reasons, the FRITZ!Box suppresses DNS responses that refer to IP addresses in its own home network. This is a security function of the FRITZ!Box to protect against what are known as "DNS rebinding attacks".

FileCatalyst TransferAgent is a client application that spins up an internal web server which can be accessed by the URL (https://localhost.filecatalyst.net) that resolves to the loopback address. When we try to resolve localhost.filecatalyst.net the FRITZ!Box will return "DNS timed out" or "DNS request timed out". This specific domain is registered to resolve to 127.0.0.1. 

Environment

FileCatalyst TransferAgent v3.5 and later.


Fritz!Box Gateway

Resolution

Configure the FRITZ!Box according to the instructions from the above article to allow an exception for the loopback address. (https://en.avm.de/service/fritzbox/fritzbox-7390/knowledge-base/publication/show/663_No-DNS-resolution-of-private-IP-addresses/)