ssh problem

fnoyan · 05-29-2006, 02:52 AM

Hi

I have two hosts connected to the same hub. I am trying to connect one host to another with ssh but the server does not respond to my connection requests.

I listen the interface of the server connected to the HUB and see that it receives the connection requests from the client.

Both hosts allow all the packets from INPUT and OUTPUT chains. The iptables configuration is as follows

Code:

 iptables -F
 iptables -A INPUT -j ACCEPT
 iptables -A OUTPUT -j ACCEPT

I can ping from one host to other from both two machines. I can connect the host machine by using a ssh client on the server. But from client to server I cannot connect!

The sshd_config files on both ends are default.

What may be the problem!

Thanks...

acid_kewpie · 05-29-2006, 02:55 AM

run tcpdump on the server and see if it recives the connections. i'd be guessing that either sshd isn't running in the first place or you have used the wrong ip address.

zeitounator · 05-29-2006, 03:01 AM

My guess is that the ssh daemon is not started on the machine you call "server". Try something like "/etc/init.d/sshd start".

If this is not the problem, a complete error message would help. Running ssh client in command line with the "-v" option might give you some valuable info as well.

fnoyan · 05-29-2006, 03:01 AM

I forget to write! I run tcpdump on the server side, the connection request packages are recevied. But the server does not respond!

The sshd daemon is running.

acid_kewpie · 05-29-2006, 03:03 AM

ok, show us your sshd_config then and the output of "ps axw | grep sshd"

mkirc · 05-29-2006, 03:16 AM

Hi,
I had the same problem, and it turned out, that Suse 10.0 and Suse 9.x have different ssh implementations.

It works with a special option, telling ssh to move to the older protocol release:

try ssh -1 <hostname>, this forces ssh to switch to version 1 of ssh-protocol !

This recommendation will only help if you have to different Linux-releases installed on cour computers !

Cheers,
Michael

fnoyan · 05-29-2006, 03:17 AM

the output of ps

Code:

 6156 ?   Ss   0:00   /usr/sbin/sshd -o PidFile=/var/run/sshd.init.pid

and the sshd_config file the only lines that are uncommented are

Code:

PasswordAuthentication no
usePAM yes
X11Forwarding yes
Subsystem   sftp   /usr/lib/ssh/sftp-server
AcceptEnv  LANG LC_CTYPE LC_NUMERIC LC_TIME LC_LOCATE LC_MONETARY LC_MESSAGES
AcceptEnv  LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv  LC_IDENTIFICATION LC_ALL

acid_kewpie · 05-29-2006, 03:25 AM

hmm, ok. well other than suggesting turning passwordauthentication on and maybe explicitly forcing protocol 2 (although i assume default is 2 then 1 anyway), if you really think that it's not responding, paste the serverside tcpdump info from "tcpdump port 22 -nv" during a login attempt on the client.

fnoyan · 05-29-2006, 03:55 AM

mkirc - thanks for advice but it did not work. I am also using SuSE (I don't like it :P, Slackware is my favorite, I use it because I hate to now!)

192.168.5.1 is the server and 192.168.5.23 is the client

Here is the output op tcpdump

Code:

10:34:42.593927 IP (tos 0x0, ttl  64, id 11375, offset 0, flags [DF], proto: TCP (6), length: 60) 192.168.5.23.8610 > 192.168.5.1.22: S, cksum 0xa854 (correct), 773442803:773442803(0) win 5840 <mss 1460,sackOK,timestamp 1499292 0,nop,wscale 2>
10:34:45.590608 IP (tos 0x0, ttl  64, id 11377, offset 0, flags [DF], proto: TCP (6), length: 60) 192.168.5.23.8610 > 192.168.5.1.22: S, cksum 0xa566 (correct), 773442803:773442803(0) win 5840 <mss 1460,sackOK,timestamp 1500042 0,nop,wscale 2>
10:34:51.590597 IP (tos 0x0, ttl  64, id 11379, offset 0, flags [DF], proto: TCP (6), length: 60) 192.168.5.23.8610 > 192.168.5.1.22: S, cksum 0x9f8a (correct), 773442803:773442803(0) win 5840 <mss 1460,sackOK,timestamp 1501542 0,nop,wscale 2>
10:35:03.590607 IP (tos 0x0, ttl  64, id 11381, offset 0, flags [DF], proto: TCP (6), length: 60) 192.168.5.23.8610 > 192.168.5.1.22: S, cksum 0x93d2 (correct), 773442803:773442803(0) win 5840 <mss 1460,sackOK,timestamp 1504542 0,nop,wscale 2>

output of iptables -L on server

Code:

Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

Chain FORWARD (policy DROP)
target     prot opt source               destination

Chain OUTPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

acid_kewpie · 05-29-2006, 04:50 AM

ok.... can you ssh to it from the server itself? using the 192.168.5.1 address? certainly doesn't show sshd responding to anything at all. do you have any other services on the box? maybe you could quickly install proftp or something, just to show the box as a whole accepts connections and it's definitly sshd's fault. i assume that nmap doesn't show the port as open.

fnoyan · 05-29-2006, 08:09 AM

Thanks for all the replies...

In one way I was able to solve the problem! I have been working on it since morning and tried lots of things! Now it is working, it is better not to touch the system

I have a new problem now...But anyway, i will have a break for networking now, have to focus on something else...

zeitounator · 05-29-2006, 08:11 AM

What's the output of "ssh -v user@server" ?

<= Sorry, just saw your last post saying you solved the problem after I posted....

acid_kewpie · 05-29-2006, 08:20 AM

Quote:

Originally Posted by fnoyan

Thanks for all the replies...

In one way I was able to solve the problem! I have been working on it since morning and tried lots of things! Now it is working, it is better not to touch the system

I have a new problem now...But anyway, i will have a break for networking now, have to focus on something else...

Well, what was it???