[FS#1334] port forwarding not working

[LEDE Bugs]

The following task has a new comment added:

FS#1334 - port forwarding not working
User who did this - Robert Muth (robertmuth)

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RE: Jo-Philipp Wich 

You could be on to something here
The machine 192.168.1.111 also has another IP 192.168.0.111
and it uses the default gateway 192.168.0.1
which goes through another router "B" which then goes through
192.168.0.1 (including double NATing)

On that machine I have:
cat  /etc/network/interfaces


auto lo
iface lo inet loopback
 
auto eth0 
iface eth0 inet static
      address 192.168.0.111
      netmask 255.255.255.0
      network 192.168.0.0
      broadcast 192.168.0.255
      gateway 192.168.0.1
      dns-nameservers 8.8.8.8
 
 
 auto enp4s0f0
 iface enp4s0f0 inet static
      address 192.168.1.111
       netmask 255.255.255.0
       network 192.168.1.0
       broadcast 192.168.1.255


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However, for debugging I have also set up port forwarding
on router B. In my desperate attempts to get things to work,
that router is running and older version of openwrt: 'OpenWrt Chaos Calmer 15.05.1' 

Same problem:

internally 

wget http://192.168.0.111:8877
--2018-02-08 07:22:28--  http://192.168.0.111:8877/
Connecting to 192.168.0.111:8877... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2711 (2.6K) [text/html]
Saving to: ‘index.html.1’

index.html.1                   100%[==================================================>]   2.65K  --.-KB/s    in 0s      

2018-02-08 07:22:28 (336 MB/s) - ‘index.html.1’ saved [2711/2711]

externally (192.168.1.116  is router B's wan IP):
 
wget http://192.168.1.116:8877
--2018-02-08 07:24:22--  http://192.168.1.116:8877/
Connecting to 192.168.1.116:8877... ^C
hangs

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1334#comment4279