SSH not accepting external connections unless port set to very high number

dave343

[H]ard|Gawd
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Oct 17, 2000
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I have a bit of a head scratcher and hopefully someone can explain what may be happening.

A few years ago I setup a router for my parents running DDWRT and with SSH. Their router has SSH set to accept connections on 443, and the primary reason is that I found it was the only port I could SSH out while at my work.

Today I was setting up another router to ship out for a family member. I have 2 ISP's I use at home, so once I had the router setup with SSH, I connected my laptop to my 2nd ISP to test the external access of SSH. I was testing it like this [ My laptop -> ISP1 ---ISP2 -> DDWRT Router SSH on 443 ]... but it wouldn't connect. Weird. I double checked and triple checked the settings, but it kept refusing the connection. If I connect my laptop to the DDWRT router (through wifi or lan), then sure I can SSH into it OK on 443, soI know the SSH service is working, but for some reason it wasn't accepting external connections outside the LAN. I then tried the default port 22, even though I think... most if not all ISP block that, and sure enough it didn't work externally. Finally after some head bashing I setup the DDWRT to accept connections on 4444....and it worked. I can now SSH into it from one ISP to another using 4444.

Ok... so obviously port 443 is for HTTPS so maybe both my ISP's at home are blocking SSH by detecting the service? But then I tried to SSH into my parents router using 443 on both ISP's and that DID work... ok so what the heck is going on... Is the DDWRT router blocking external connections on 443 and 22..? If I can still SSH into my parents router using 443 then my ISP isn't blocking the service... so what's up with my router then?
The router I setup was an older Linksys E2500 running Firmware: DD-WRT v3.0-r33772 mega (11/16/17) This is the latest firmware for this router. Note: I have used this router for years myself on port 443 to SSH into it from everywhere, all I did was factory default it and reset it up.
Thanks in advance.

The router I setup was a older Linksys E2500 running Firmware: DD-WRT v3.0-r33772 mega (11/16/17) This is the latest firmware for this router and I have previously used this router for years with SSH enabled on 443, no issues, so it's not like this firmware has had issues with SSH on 443, or 22 externally.
 
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