NAT loopback debugging help wanted

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gb777 wrote:

So I found out the NAT loopback works if the connection from the router to the server being accessed is via one of the ethernet ports on the device (rather than through an intermediate switch).  I also found out that this is likely due to the

bridge-nf-call-iptables

setting, based on information in a forum of a different consumer device.

 

That is, if you issue:

echo 0 > /proc/sys/net/bridge/bridge-nf-call-iptables

it will work (just as if you turn on promisc mode on br-lan).

So this is interesting.  The RBR 750 uses Linux's virtual bridging (a software implementation of Layer 2 switching) to connect the 3 physical ethernet ports (eth1, eth2, eth3) and the wireless interfaces into a single bridge interface. The problem is not the type or kind of switch, it's the fact that those packets cannot be sent directly to their layer-2 receiver.  I don't fully understand it yet.

 

 

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So I've been working with Netgear Tech Support on this, too.  They were friendly enough to let me describe the problem.  I mentioned to them that setting bridge-nf-call-iptables to 0 fixed the issue.

Now, they've sent me a custom firmware to try.  Of course, only under an NDA.  Not the kind where you can't talk about it, just the kind where you can't share the trial software they shared. I install the firmware and guess what, it now works....

so I took a closer look at how they've changed the configuration in the new firmware. 

I've compared the iptables before and after, and they're identical. I do not know if they've made other changes in the trial firmware, except that ....

... the trial firmware has bridge-nf-call-iptables set to 0.