Problem with connecting to SSH server

[hwang251]

I created an openssh-server on ubuntu, but when I try to ssh it from another computer I get this message:

ssh: connect to host "ip_address" port 22: No route to host

where ip_address is my the server's ip_address

[NateMan]

Well that message is telling you that the ip address of the server your connecting to isn't there or the port your attempting to connect to isn't open. How did you enter the command? was it in the form of ssh usrname@host/ipaddress? Is your ssh set to a different port than default or are you going through a firewall? Is the software firewall on your ubuntu box turned on? Give me a little more info and this should be easy to fix.

[hwang251]

Well that message is telling you that the ip address of the server your connecting to isn't there or the port your attempting to connect to isn't open. How did you enter the command? was it in the form of ssh usrname@host/ipaddress? Is your ssh set to a different port than default or are you going through a firewall? Is the software firewall on your ubuntu box turned on? Give me a little more info and this should be easy to fix.

I entered the command in the terminal and in the form of ssh usrname@host/ipaddress.

There is no firewall and the port is set to 22.

And the software firewall is not turned on

[tigerplug]

Can you ping the hostname/ip address?

[NateMan]

Is the server on the local network or are you trying to connect to a remote server? pinging is a good next step.

[hwang251]

Can you ping the hostname/ip address?

no

but the connection on the server is working, because I can ping a website

[NateMan]

can you get on the machine locally and check the ip address with ifconfig? I've had one reset a static ip address before I rebooted it for the first time before.

[hwang251]

can you get on the machine locally and check the ip address with ifconfig? I've had one reset a static ip address before I rebooted it for the first time before.

Yes I can get on the machine locally and the ip address is still the same

[NateMan]

have you checked your /etc/network/interfaces, /etc/hostname, and /etc/resolv.conf? They should all match. also did you use the computers hostname or its ip address?

[NateMan]

Also have you tried a reboot? I know that is frowned on, but sometimes if the problem is really odd and can't be fixed by normal means, then it might help.

[hwang251]

have you checked your /etc/network/interfaces, /etc/hostname, and /etc/resolv.conf? They should all match. also did you use the computers hostname or its ip address?

They matched

And I used the computer's ip address

[NateMan]

Well... can you ping out from the server? try to ping www.google.com or something. If that doesn't work, have you rebooted it since setting it up? Its worth a shot. I'd also check physical connections, although that is highly unlikely. What about pinging it from another machine on the network? What sort of box are you pinging from? I'd look at your local machine if you can ping out, but not into the box.

[MJN]

[can you ping the hostname/ip address?]

no

but the connection on the server is working

You need to find out why. If there's no firewall running then you should be able to ping. If you can't then you won't be able to SSH in either.

Describe your network layout, including all IP address and subnet mask details.

Mathew

[hwang251]

You need to find out why. If there's no firewall running then you should be able to ping. If you can't then you won't be able to SSH in either.

Describe your network layout, including all IP address and subnet mask details.

Mathew

The network is through the school's network I'm at.

The ip address is the one found in ifconfig

[MJN]

That's no help at all unfortunately...

What is the IP address and mask of the client? And the server?

Also show the output of ip route on both machines.

A traceroute from the client to the server might also be useful too (traceroute <server ip>)

Mathew

[NateMan]

Yes please post the information about the network. There shouldn't be anything of a security risk in that at all, since we would need the public ip address. That's on your router. Your on a school network? Do you know what their firewall does? It may not allow pc to pc connections of any kind.

[hwang251]

For security I got rid of the traceroute

[hwang251]

And when I run traceroute from server to client I get
all stars ***

[MJN]

Given the client and server are on completely seperate networks it looks like there are restrictions in place controlling what traffic types can be transited. ICMP ping restrictions are commonplace, but you would need to check with your network administrator whether SSH access to your server is allowed.

Mathew

[NateMan]

Yeah... that's because those are private addresses and traceroute only shows so many of those, obviously enough that it never gets to the non-private ones from the server. Please post your network information if you want accurate help. However, since that works, I imagine that your not allowed over the schools network to ssh into other boxes, if everything is setup correctly on your end. School networks are normally NOT designed to have people throwing up their own servers and eating up all that juicy bandwidth.

[hwang251]

Given the client and server are on completely seperate networks it looks like there are restrictions in place controlling what traffic types can be transited. ICMP ping restrictions are commonplace, but you would need to check with your network administrator whether SSH access to your server is allowed.

Mathew

Even though we setup the server ourselves?

[NateMan]

also, I personally wouldn't post a traceroute from my box in a forum. That's public ips. You wouldn't even post your local network information.

[MJN]

That's public ips.

Exactly, hence there is no security in trying to keep them 'secret'.

Even though we setup the server ourselves?

Yes. It sounds like it's a network issue (most likely by design given you've confirmed both machines have got network access). I trust you've confirmed the SSH server is working by SSH'ing to localhost on the server? (not that this would produce the same error)

Mathew

[MJN]

Yeah... that's because those are private addresses and traceroute only shows so many of those, obviously enough that it never gets to the non-private ones from the server.

They are not private addresses. The stars indicate a timeout i.e. the absence of an ICMP echo response within an acceptable time limit. The most likely cause for this is the (common) blocking of ICMP traffic on many Internet-connected routers. This is why the usefulness of ping is limited these days (whilst a positive response can be helpful a negative one means very little).

Mathew

[NateMan]

My bad, I meant private jumps, as in they were blocked. I personally wouldn't want to draw any attention to my specific server on a school network, just because of temptation to other students on the local network. Every campus has some issues with this.