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Follow up question on What is the NAT traversal technique used by bitcoin.

The network architecture described here https://superuser.com/questions/1109859/2-routers-connected-in-series-and-port-forwarding is something that I (probably) have in my home (and probably 99% of other people):

Internet > ISP router (NAT 1) > My home router (NAT 2) > My Node

So my Node is hidden behind 2 NATs. Therefore I should forward ports on both routers to allow incoming connections to my Node.

But people have no access to NAT 1 and can only port-forward NAT 2, and must probably contact ISP to port-forward NAT 1.

How do people run their nodes with incoming connections enabled when this issue is present?

EDIT: In discussion with lenlord it seems that his ISP's router does not perform NAT and that his home router has (dynamically) assigned public Internet address. Is this the standard configuration ISP's provide for homes.

EDIT2: After contacting the ISP and reading some forum posts I found out that I'm indeed behind their NAT (NAT 1 in picture, so called CG-NAT), but that they can remove it for me for free.

  • is the ISP router installed at your place? You should have access and be able to configure it. Typically, I set the ISP router to operate in bridge mode and just let my router do all the NAT. – renlord Oct 30 '17 at 14:30
  • I have my home router in my home but there should also be a router that ISP controls that many homes are connected to (and operates as NAT, so ISP does not need to have 100 public addresses for 100 homes in my building). – croraf Oct 30 '17 at 14:37
  • that's the first time i've encountered such an arrangement. I guess you'll have to ring up your ISP then. – renlord Oct 30 '17 at 14:47
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In discussion with @lenlord it seems that his ISP's router does not perform NAT so that his home router has (dynamically) assigned public IP address.

After reading some forum posts and contacting the ISP I found out that some ISPs (and mine is one of them) do indeed hide households behind their NAT (NAT 1 in picture, so called CG-NAT), but that they can remove this NAT for free on demand.

Remove this NAT on the ISP's router is needed to operate bitcoin node with incoming connections.

  • It is common elsewhere in the world for NAT2 to be only a switch rather than a router in a home setup if it is used at all. It is also just as common there for the customer to have full access to NAT1 which is commonly a wi-fi enabled ADSL/VDSL modem router. – Willtech Jan 31 '18 at 7:53
  • Further, many can use Tor without port forwarding and this will allow also incoming connections when correctly configured. – Willtech Jul 7 '18 at 5:13
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Whatever is between your computer and your public IP has to be forwarded.

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