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Can Ping out, can't ping in. [RESOLVED,but no understanding]
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Illiander
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PostPosted: Tue Apr 10, 2018 9:56 am    Post subject: Can Ping out, can't ping in. [RESOLVED,but no understanding] Reply with quote

I'm installing Gentoo on a new laptop, and to make things easier on me, I was going to get it to the point where I could just ssh into it from my desktop and then handle everything from there.

But although my laptop can ping my desktop, my desktop cannot ping my laptop, nor can it ssh in (yes, I've turned on the ssh daemon, and set a known root password). ssh just hangs, and ping reports 100% packet loss.

What do I need to change on my laptop to fix this?


Last edited by Illiander on Sat Apr 14, 2018 9:52 am; edited 1 time in total
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NeddySeagoon
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PostPosted: Tue Apr 10, 2018 10:35 am    Post subject: Reply with quote

Illiander,

Do you have a route both ways?
Post the output of
Code:
route -n


Is there a firewall on the laptop.

Can the laptop ping itself by its real IP?

Do not use root passwords with ssh. Its not safe.
If you must use passwords, make a normal user with a hard to guess user name and a nice long passphrase, then use sudo or su to get root.
Better yet, use key based ssh login.

Not using the default port will make your ssh logs more readable but it won't improve your security.
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Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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Hu
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PostPosted: Wed Apr 11, 2018 1:39 am    Post subject: Reply with quote

Are both systems on the same subnet? Unidirectional traffic suggests that the laptop is actively refusing to respond to unsolicited traffic or that some device along the path is filtering the traffic on the laptop's behalf. What OS is the laptop running? Gentoo minimal install CD? System Rescue CD? Something else? If you have traceroute on both systems, have each one traceroute to the other. For a simple home network, the paths ought to be reflections of each other. The desktop->laptop traceroute will almost certainly stop partway through, given that neither ping nor ssh works. However, knowing the last responsive node and first unresponsive node may be useful.
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szatox
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PostPosted: Wed Apr 11, 2018 11:02 pm    Post subject: Reply with quote

iptables -P INPUT DROP behaves like that. Perhaps a misconfigured firewall?
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Illiander
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PostPosted: Sat Apr 14, 2018 9:42 am    Post subject: Reply with quote

Laptop is running a Gentoo liveCD from an external USB.

Rebooted the laptop today, with all things plugged in, and it now responds to ping. I'm going to assume that that's a boot/network restart inequality.

Still doesn't respond to ssh.

Going to go look up the make user process, see if it's just refusing to respond to ssh root.

---

And it's not just refusing to respond to root, it's refusing to respond to ssh.

Cleared out iptables (iptables -F, -X, -Z), and it's still refusing to respond to ssh.

Now I'm really getting lost.

---

Edit: And now somehow it's working.

Absolutely no clue how it's working though.
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NeddySeagoon
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PostPosted: Sat Apr 14, 2018 2:49 pm    Post subject: Reply with quote

Illiander,

The Gentoo minimal CD does not start sshd for you.
You need to do it yourself.

Once sshd is started on the Gentoo minimal CD, root logins over ssh are set to prohibit-password, so only key based root logins work.

System Rescue CD and the Gentoo LiveDVD are a bit more user friendly in that respect.
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Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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Illiander
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PostPosted: Sat Apr 14, 2018 4:12 pm    Post subject: Reply with quote

I knew that, and *did* start sshd manually.

Quote:
Once sshd is started on the Gentoo minimal CD, root logins over ssh are set to prohibit-password, so only key based root logins work.


Not quite sure what this means.
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