XPost: comp.mobile.android, alt.comp.os.windows-10   
   From: patrick@oleary.com   
      
   On Wed, 21 Feb 2024 10:47:12 +0000, Graham J wrote:   
   > Patrick wrote:   
   >> Desktop PC to Android Mobile Hotspot - What do you use for the Gateway?   
   >> 1. My Windows 10 desktop has no Wi-Fi card.   
   >> 2. So I Ethernet out to an old router acting as a wireless client bridge.   
   >   
   > I'm confused by the terminology.  I would expect "wireless client" to be   
   > sufficient.   
      
   Strictly speaking, DD-WRT calls the setup I've been using for years a   
   "Repeater Bridge", which means it's a bridge and it's also a repeater.   
   https://wiki.dd-wrt.com/wiki/index.php/Repeater_Bridge   
      
   Here's the scenario so you can visualize the setup.   
   1. The Windows 10 desktop PC has no Wi-Fi card but it has Ethernet   
   2. So, the desktop "thinks" it's using Ethernet all the time   
   3. The desktop PC has a static IP address (for simplicity)   
   4. Let's call that static IP address 192.168.1.4   
   5. This is because it's the fourth item after the modem   
   6. The 3rd item after the modem is the DD-WRT "Repeater Bridge"   
   7. So let's assign that DD-WRT repeater bridge the address 192.168.1.3   
   8. That DD-WRT repeater bridge connects on 2.4GHz to a 2.4GHZ AP   
   9. So let's assign that 2.4GHz Ap the IP address 192.168.1.2   
   10. It's a minor detail but the Ethernet out of that AP goes to a switch   
   11. But a switch operates at the MAC address level so the IP passes through   
   12. The switch is wired to the main router which is IP address 192.168.1.1   
      
   To summarize in fewer words, the "Internet" cat5 cable comes out of the   
   modem to the 192.168.1.1 router whose cat5 cable goes to the switch whose   
   cat5 cable goes into the access point at 192.168.1.2 which is wirelessly   
   bridged to the DD-WRT "Repeater Bridge" at 192.168.1.3 whose cat5 cable   
   goes into the Windows PC at 192.168.1.4.   
      
   As you seem to have understood, the DD-WRT could have been set up as what I   
   think DD-WRT calls a "Station Bridge" but as shown in the link above, a   
   "Station Bridge" is a bridge plus it allows the integrated switch to work   
   on the router so that wired clients can attach to it (like the desktop PC).   
      
   But since the desktop is far away from everything else, I figured I'd set   
   up the DD-WRT router to also act as a 2.4 GHz access point for nearby   
   devices to connect to (either wired or wirelessly) - so it's actually set   
   up as both a bridge and as a repeater (which really have nothing to do with   
   each other). It's a repeater. And it's a bridge. Two different things.   
      
   1. The DD-WRT repeater bridge connects to the access point wirelessly   
   2. But also the DD-WRT repeater bridge allows Ethernet to connect to it   
   3. And the DD-WRT repeater bridge allows wireless clients to connect too   
      
   It's really a good use of an old router if you need to have an access point   
   & an Ethernet switch all in one when you're far away from the main router.   
      
   >> 3. This has been working for many years.   
   >   
   > OK so what is the internet router it normally connects to?   
   > And what LAN IP address does it have?   
      
   See above description, depicted below:   
   Modem->Router->Switch->AP->Bridge->PC   
   Internet->192.168.1.1->switch->192.168.1.2->192.168.1.3->192.168.1.4   
      
   Everything is wired via cat5 except the connection between the access point   
   and the bridge is over 2.4GHz channels. For our purposes, we can ignore the   
   switch as it's just a pass-through device, so the circuit simplifies to:   
   Modem->Router->AP->Bridge->PC   
   Internet->192.168.1.1->192.168.1.2->192.168.1.3->192.168.1.4   
      
   I don't know if I understand bridges well enough to say the next statement,   
   but I think even the bridge is a pass-through device, so it simplifies   
   further to something like this.   
   Modem->Router->AP->PC   
   Internet->192.168.1.1->192.168.1.2->192.168.1.4   
      
   But I'm not sure of that. If I trace the route from the PC through the   
   bridge and access point and switch to the router, let me see what happens.   
      
   Well that was unexpected.   
      
   tracert 192.168.1.1   
   Tracing route to 192.168.1.1 over a maximum of 30 hops   
   1     1 ms     1 ms     1 ms  192.168.1.1   
   Trace complete.   
      
   The traceroute didn't see any of the intervening devices.   
   Is that how it's supposed to work?   
      
   >> For whatever reason, the Internet went out.   
   >   
   > To avoid confusion, power off this router while the internet is dead.   
      
   That's a good idea. Too late now. The Internet came back. :)   
   So I'm back on the repeater bridge setup that has been working for years.   
      
   >> So I set up the phone as a   
   >> Mobile Hotspot which works for the laptop.   
   >   
   > What LAN IP address does this laptop report when connected to the hotspot?   
      
   I think you hit the nail on the head. The laptop must be in a different   
   subnet. Let's say the cellular company is on 1.2.3.4, then the laptop will   
   likely be on 1.2.3.x which I think is probably what my problem was.   
      
   I guess the DD-WRT "Repeater Bridge" is on the wrong subnet because it's on   
   192.168.1.3 while the cellphone acting as a mobile hotspot is likely on   
   1.2.3.x - so they're completely different networks (I think).   
      
   There must be a way around this so I'll look up, for the future, how to   
   connect a mobile hotspot to a DD-WRT repeater bridge.   
      
      
   >> But I wanted the desktop to be connected also.   
   >> 1. So I figured I'd set up the bridge, temporarily to the Mobile Hotspot.   
   >> 2. The Mobile Hotspot has an SSID with the same passphrase as all my APs.   
   >   
   > I think this is very confusing.  I think you should change its SSID to   
   > be obviously different - "Hotspot" - and specify a different passphrase.   
      
   I don't think the mobile hotspot passphrase matters at all as I originally   
   set the mobile hotspot up without any security which worked for the laptop   
   but the DD-WRT "Repeater Bridge" wanted an SSID and a passphrase so I set   
   up the mobile hotspot with a passphrase to satisfy the DD-WRT demands.   
      
   I don't think it would have mattered what the SSID was either for the   
   mobile hotspot but I made the SSID unique so there would be no confusion.   
      
   > Then change the old router's wireless credentials to the values required   
   > for the hotspot.   
      
   I think the problem is the subnet mismatch between the static IP address on   
   the DD-WRT "Repeater Bridge" and the mobile hotspot IP address.   
      
   The Internet came back but for the future I need to look up the procedure.   
   https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320483&sid=94d54   
   563853901558e5142236cfda87   
      
   >> There's also a question in the DD-WRT wireless client bridge setup of:   
   >> Local IP Address = 192.168.1.whatever/24   
   >> Gateway = 192.168.1.1   
   >> Local DNS = 192.168.1.1   
   >   
   > The LAN IP address for the wireless client can only be used for   
   > communication with the client itself.   The DHCP service should be off,   
   > which means that to communicate with the wireless client your computer   
   > needs a static address of the form 192.168.1.another.  The "gateway"   
      
   [continued in next message]   
      
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