mjhjmtu

Unable to ssh to another computer but can ping it? Not sure what I am missing?

Using a Netgear router

bash-3.2$ ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
 inet6 ::1 prefixlen 128 
 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 
 inet 127.0.0.1 netmask 0xff000000 
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
 ether xx:xx:xx:xx:xx:xx 
 media: autoselect (none)
 status: inactive
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
 ether xx:xx:xx:xx:xx:xx 
 inet6 xxxx::xxxx:xxxx:xxxx:xxxxxx prefixlen 64 scopeid 0x5 
 inet 10.0.0.3 netmask 0xffffff00 broadcast 10.0.0.255
 media: autoselect
 status: active
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078
 lladdr xx:xx:xx:xx:xx:xx:xx:xx 
 media: autoselect <full-duplex>
 status: inactive
bash-3.2$ ssh jeremy@10.0.0.4
ssh: connect to host 10.0.0.4 port 22: Connection refused
bash-3.2$ ssh -p 5900 jeremy@10.0.0.4
ssh: connect to host 10.0.0.4 port 5900: Connection refused
bash-3.2$ ping 10.0.0.3
PING 10.0.0.3 (10.0.0.3): 56 data bytes
64 bytes from 10.0.0.3: icmp_seq=0 ttl=64 time=0.046 ms
64 bytes from 10.0.0.3: icmp_seq=1 ttl=64 time=0.079 ms
64 bytes from 10.0.0.3: icmp_seq=2 ttl=64 time=0.078 ms
64 bytes from 10.0.0.3: icmp_seq=3 ttl=64 time=0.077 ms
64 bytes from 10.0.0.3: icmp_seq=4 ttl=64 time=0.079 ms
64 bytes from 10.0.0.3: icmp_seq=5 ttl=64 time=0.081 ms
64 bytes from 10.0.0.3: icmp_seq=6 ttl=64 time=0.078 ms
^C
--- 10.0.0.3 ping statistics ---
7 packets transmitted, 7 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.046/0.074/0.081/0.011 ms
bash-3.2$ ping 10.0.0.4
PING 10.0.0.4 (10.0.0.4): 56 data bytes
64 bytes from 10.0.0.4: icmp_seq=0 ttl=64 time=2.667 ms
64 bytes from 10.0.0.4: icmp_seq=1 ttl=64 time=2.675 ms
64 bytes from 10.0.0.4: icmp_seq=2 ttl=64 time=2.969 ms
64 bytes from 10.0.0.4: icmp_seq=3 ttl=64 time=2.663 ms
64 bytes from 10.0.0.4: icmp_seq=4 ttl=64 time=2.723 ms
^C
--- 10.0.0.4 ping statistics ---
5 packets transmitted, 5 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 2.663/2.739/2.969/0.117 ms
bash-3.2$ 

The server is either not running sshd (and hence not listening on port 22) or has a firewall blocking port 22 (the default ssh port), or in incredibly rare cases running ssh on some other port (which is almost certainly not the case).

First check to make sure sshd is installed (using debian examples)

sudo apt-get install openssh-server

And if so, is it running:

ps -ef | grep sshd

then check to see if it is listening to port 22

sudo netstat -nlp | grep :22
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 946/sshd
tcp6 0 0 :::22 :::* LISTEN 946/sshd

then check your firewall rules (this varies significantly, so I'll show a debian/ubuntu/etc example):

sudo ufw status

sudo ufw show listening
tcp:
 22 * (sshd)
 24224 * (ruby)
tcp6:
 22 * (sshd)
 8080 * (java)
udp:
 123 10.X.Y.Z (ntpd)
 123 * (ntpd)
 18649 * (dhclient)
 24224 * (ruby)
 34131 * (ruby)
 60001 10.87.43.24 (mosh-server)
 68 * (dhclient)
udp6:
 123 fe80::1031:AAAA:BBBB:CCCC (ntpd)
 123 * (ntpd)
 48573 * (dhclient)

If ufw shows it as closed then run (again a debian/ubuntu example)

sudo ufw allow 22

Kind of a weird shot-in-the-dark, but make sure your IP didn't change. I had this issue once - I set a .bashrc alias alias sshdev='ssh me@123.2.3.4' as my typical way of logging in, and one day I started getting the following error:

ME-M-216C:~ me$ sshdev 
ssh: connect to host 123.2.3.4 port 22: Connection refused

We just had a power outage at work which reset the IP's, so I was successfully pinging an IP but it wasn't the correct machine. You can use nslookup <IP> to make sure it's the correct machine name that you're trying to ssh into.

When you get the message "connection refused", that means that a daemon is not listening on that port or a firewall is rejecting the connection. To resolve the issue, ensure that ssh is running and the local firewall rules are not rejecting incoming connections on that port.

I had the same issue with Linux Lite. In order to fix the issue, I had to access Settings > Firewall Configuration. After signing into root, I changed the incoming setting to Allow and it worked.

Two thoughts.

1. Does the firewall allow connections on port 22 to the machine?


2. Is the ssh daemon (sshd) running?

this command worked for me. Try this.

update-rc.d -f ssh enable 2 3 4 5

Steps followed in general:
1) ping to the destination host and verify and cross check IP address entered.
2) Check sudo service sshd status on both the hosts. If stopped, start the sshd service. If you get an error sshd.service not found, install openssh-server -> sudo apt install -y openssh-server and restart the sshd.service
3) Disabling the firewall or making changes to the config files should be considered the last option.