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Thread: Trying to get DDNS to work but cant update package list

  1. #11
    New Member
    Join Date
    Jul 2019
    Portland, OR
    ah ok, that first part makes sense. My router doesn't have a profile for FreeDNS, but it has a custom profile where I can add my login, so I switched the DNS to direct to my external IP address. Sorry I'm not great with network stuff. Could you help me with the port forwarding part? I'm not sure exactly what you are saying by the dirty side of my router. So on my port forwarding page on my router right now I just have one entry and it is the HM IP address and port 443 forwarded. How should I change that?

  2. #12
    TVWBB Pro
    Join Date
    Jun 2016
    Southeastern MN
    Let's see if I can do this in 10 minutes..... (and I failed, it's now 2 hours later.)

    General theory, first. For TCP/IP communications, you use both an x.y.z.t IP address, as well as ports at that address. You'll have a ip/port pair at each end of the connection. Yes, I'm not going to talk about subnet masking, Multicast, etc., those will just confuse the issue. There is a series of IP addresses, originally defined in RFC1918, that will never be available on the public Internet, and will always be safe for use behind a Network Address Translating firewall (again, a more advanced topic.) The short story is that a NAT firewall allows you to run an RFC1918 network in your home, and present a single IP address to the world (it plays games with ip/port pairs and connections.) IP addresses really don't have any particular significance, although there are some geo-locating facilities & the like. Ports, on the other hand, have some structure. A target port should be a "well known" port. HTTP uses 80, HTTPS uses 443, SSH uses 22. The source port on the originating side will be some random port picked by the operating system. BTW, my use of the term "dirty" refers to the public Internet, as it's a big bad ugly world out there and no one can be trusted.

    Let's break this down, for what does need to happen to get a remote connection to work. The browser will do a name service lookup for your HM external name (FreeDNS,) and make a connection to HMDirty:80. HMDirty is the IP address that your home router uses on the public network side. Your router needs to have a port forward, from HMDirty:80 to your internal HMaddress:80. Think of it this way: The initial packet connection is like a package delivery to a gated community. It comes to the gatehouse (your router) and gets direction to the right house (IP address) and doorway (port.) Every inbound packet talks to the gatehouse (HMDirty) and a particular door, and the guard there knows how to get the package to the right house (HeaterMeter.) You can (and I do sort of suggest this) pick a different inbound port other than 80 (different door at the gatehouse) and still forward to your internal HeaterMeter on port 80.

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