Unable to forward specific ports

An area specifically for port forwarding, firewalls and other (on-line) security related issues.
Post Reply
Posts: 1
Joined: Sun Jan 29, 2012 2:51 pm

Unable to forward specific ports

Post by george2011 » Sun Jan 29, 2012 3:07 pm


I am new, and I sure hope that someone can explain to me what is happening. First of all my setup. As I am involved with highly confidential information, I work behind a double NAT, ISPs modem/router ( and a Linksys E4200 ( connected with WAN to 1st router's LAN. In my subnet I have a Synology DS212+ NAS, with static local IP.
Ports with which I had no issue forwarding are 21, 22, 23, 25, 80, 110, 139, 445, 5000, 5001, but for 139 and 445 I had to disable the firewall.
Ports that won't budge are 143, 443, 873, 5005, 5006, 7000, 7001, 137, 138, 1723 and 1194. I have tested the 2 routers separately, and in double NAT, and result is the same. The ports stay closed on both routers.
I have spend time on the phone with Linksys tech support, but no response. I have talked to the ISP's tech support multiple times, but the people there don't even know what a NAS is used for. One time they hang up on me, another time they told me to research the internet. I sure hope that we have on this forum some experts that are motivated enough to take this challenge and help it being resolved. :idea:
Looking forward to reactions, and a big thanks in advance. :roll:
RouterTech Team
RouterTech Team
Posts: 3753
Joined: Wed Jan 10, 2007 11:54 pm

Re: Unable to forward specific ports

Post by mstombs » Tue Jan 31, 2012 11:30 pm

Not sure what double nat has to with confidentiality - you need secure comms via vpn to encrypt traffic end-to-end.

Double-nat is a big problem with port forwarding as you need to add compatible port forwarding on both routers - not sure what device you have "disabled the firewall" because routers often use the iptables netfilter 'firewall' to implement port forwarding - to bypass the firewall you should try to use a dmz on both, if available.

You can't port-forward onto ports in use - the E4200 has usb ports and can act as NAS as well can't it - so it may be trying to offer services in conflict with your NAS? There is 3rd party firmware available for the E4200 - they may give you more control - assuming you can get past ISP modem/router.
Post Reply