WRT3200 SSH: remote side unexpectedly closed the connection

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pickler
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Joined: 19 Aug 2022
Posts: 21
PostPosted: Thu Dec 15, 2022 15:36    Post subject: WRT3200 SSH: remote side unexpectedly closed the connection Reply with quote
Firmware: DD-WRT v3.0-r50963 std (11/28/22)
WRT3200ACM

I tried to upgrade my firmware today but the router is refusing SSH connection. I have SSH in services and administration both enabled. However I'm always getting remote side unexpectedly closed the connection error when trying to connect with Putty. i have tried rebooting and using different browsers. never had this issue before.
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ho1Aetoo
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Joined: 19 Feb 2019
Posts: 3002
Location: Germany
PostPosted: Thu Dec 15, 2022 15:50    Post subject: Reply with quote
https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=333333&start=0

egc wrote:
If you have trouble connecting with SSH then download the latest Putty and make sure under SSH/Host keys to move ed25519 to the top and probably untick "Prefer Algorithms for which a host key is known" or forget the HOST keys
If you have trouble connecting with WinSCP under Tools/Clean up Clear Cache
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pickler
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Joined: 19 Aug 2022
Posts: 21
PostPosted: Thu Dec 15, 2022 15:55    Post subject: Reply with quote
ho1Aetoo wrote:
https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=333333&start=0

egc wrote:
If you have trouble connecting with SSH then download the latest Putty and make sure under SSH/Host keys to move ed25519 to the top and probably untick "Prefer Algorithms for which a host key is known" or forget the HOST keys
If you have trouble connecting with WinSCP under Tools/Clean up Clear Cache


i already tried this and it didn't work. what i found i had to do was change the default gateway address from 192.168.1.1 to 192.168.3.1. i'm not sure why but this helped. thanks.
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ho1Aetoo
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Joined: 19 Feb 2019
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Location: Germany
PostPosted: Thu Dec 15, 2022 16:05    Post subject: Reply with quote
Only the fingerprint of the router must be deleted from the "known_hosts".

If you change the address of the router it works of course also because for the new address there is no fingerprint stored.
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pickler
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Joined: 19 Aug 2022
Posts: 21
PostPosted: Thu Dec 15, 2022 16:06    Post subject: Reply with quote
ho1Aetoo wrote:
Only the fingerprint of the router must be deleted from the "known_hosts".

If you change the address of the router it works of course also because for the new address there is no fingerprint stored.


ok thanks, I never had to do this before, is this a new thing?
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ho1Aetoo
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Joined: 19 Feb 2019
Posts: 3002
Location: Germany
PostPosted: Thu Dec 15, 2022 16:20    Post subject: Reply with quote
actually not, every ssh server has a fingerprint, which is generated when you install the server for the first time.

When you reinstall the server a new fingerprint is generated.

So I personally had to delete "fingerprints" very often.
Nothing unusual...

the format of the host_key has simply changed.
dd-wrt now uses ed25519 as host_key...

ed25519 is another encryption based on elliptic curves and it is much faster with the same or better security
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