I have 2 identicaly cfg synology routers at DE and CZ location.
DE router allows create/renew LE certificate - CZ not
routers cfg: no port fowarding, no UPnP, port 80 cfg as open
port80 looks open (tested by nmap, telnet) at both routers
port80 looks blocked (common web tools) at both routers
renew certificate by tunnel one router to the second location
CZ router -> l2tp tunnel -> DE router (create/renew OK)
DE router -> l2tp tunnel -> CZ router (create/renew PROBLEM)
.. se we can exclude HW or other stupid issue.
- reverse domain DNS lookup: both DE, CZ looks OK but how to check and where to look that routing is OK?
- any idea how to analyze the botleneck at CZ end point? .. to check why it does not renew certificate
- what else could affect certificate create/renew ?