Can't Login using SSH

[noob_for_life]

I'm running Knoppmyth at home. Whenever I attempt to ssh into the box

ssh myuserid@IP.AD.DR.ESS

my terminal session hangs for a long time. Then, one of two things happens:

1) Most of the time, I get a response "Write failed: Broken pipe" and go back to a command line.
2) Sometime, I get a request for a password. After I type it in and hit enter, I am told that"

Connection closed by IP.AD.DR.ESS

Newbie that I am, I don't know what log files to check on the machine to find indicators of the problem.

Can anyone tell me where to look to ID the error on the server side and advice on what I might do about it?

Thanks for your help.

Gary

[sdimhoff]

Hmm, I can't say I recognize exactly what the problem is, but I have a couple of questions for you.

1.) Are you sure that you've configured your /etc/ssh/sshd_config file correctly. If you are getting to your computer, the authentication may not be set up correctly to actually let you in. Although I would think the error messages would be different if that were the case.

2.) If you are behind a router and on a network, have you tried to connect to the machine via ssh INSIDE your network?

The reason I ask this has to do with connection speed. Normally this shouldn't be any issue, but I find it odd that you are obviously connecting to your computer but it is hanging for a long time. To check the speed of the connection you should try pinging it. If your latency is very high then your sshd server may be kicking it?

3.) Also, are either you or your linux box behind a firewall that could be messing with the connection?

[asidu]

Are you trying to ssh from another machine or you local machine.

Can you frist try to see if you can SSH from the local machine.
That will confirm that your SSH server is working fine locally.

Hope that helps.

[noob_for_life]

Thank you both so much for your help on this.

Are you sure that you've configured your /etc/ssh/sshd_config file correctly.

The file hasn't been touched since I set up the box. And until this, I had been using SSH freely for most of a year. The problem is recent and the time stamp on the file is from 12/2006. So, I assume it is OK.

If you are behind a router and on a network, have you tried to connect to the machine via ssh INSIDE your network?

Thanks for pointing this out. I should have said so up front. I am inside my network along with the Linux/Knoppmyth box.

Also, are either you or your linux box behind a firewall that could be messing with the connection?

My Linux box and I are on the same network. I can ping it and get a very fast response. There is no firewall between us. I should experiment with a crossover cable. I'll try to do that later. I don't believe our router could be messing with the connection.

Are you trying to ssh from another machine or you local machine? Can you first try to see if you can SSH from the local machine.

I am trying to ssh from my laptop (a Mac) into the Knoppmyth Linux box. I can successfully ssh from the laptop into other boxes without a problem.

When, on the Knoppmyth box, I do

ssh 127.0.0.1

it works perfectly. But, if I try to ssh from the Knoppmyth box into another computer on our network, it takes a very long time to connect. Still, I can connect successfully. If I ssh to a server far off the network (say to our web site hosted somewhere in the midwest), it gets there much more quickly.

After having rebooted the Knoppmyth box, I tried to ssh into it from various computers on our network. They all took a long time to get a response from the Knoppmyth box, as does my laptop (like 90 seconds). But, they would occasionally be able to log in.

I hope all of this gives you guys some clues as to where I should look.

Thanks again!

Gary

[asidu]

The fact that you can SSH from your local machine means the server set up is ok.

Sounds like a network problem.

You could use a cross wire and plug your laptop direct into the Knnopmyth Box to experiment the connection speed.

Could you print the routing tables for your two machines and post the results.

Login in root and capture output of the following commands

#ifconfig

#netstat -nr

Secondly, if you have a hub, connect the SSH server and your laptop to it.
Test the SSH and see how is the speed. That will confirm if your router/firewall is causing the long delay that you have mentioned.

Good luck !

[noob_for_life]

I tried the crossover cable (I have a hub, but it's tough to get to).

ssh got me in right away!

Wow. Thanks!

Any ideas on how I track down the network problem? I have tried to ssh to a third local computer from both the Knoppmyth box and from my laptop. Again, long lag. No login.

In the next message, I'm posting the routing tables for my laptop and the Knoppmyth computer. Are they meaningful, now?

Thanks!

Gary

[noob_for_life]

Local Machine (laptop) ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULT ICAST> mtu 1500
ether 00:11:24:36:c2:f8
media: autoselect (none) status: inactive
supported media: none autoselect 10baseT/UTP <half-duplex> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-duplex,hw-loopback> 1000baseT <full-duplex> 1000baseT <full-duplex,hw-loopback> 1000baseT <full-duplex,flow-control> 1000baseT <full-duplex,flow-control,hw-loopback>
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULT ICAST> mtu 1500
inet6 fe80::211:24ff:fe8e:e8dc%en1 prefixlen 64 scopeid 0x5
inet 10.10.12.114 netmask 0xffffff00 broadcast 10.10.12.255
ether 00:11:24:8e:e8:dc
media: autoselect status: active
supported media: autoselect
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULT ICAST> mtu 4078
lladdr 00:11:24:ff:fe:36:c2:f8
media: autoselect <full-duplex> status: inactive
supported media: autoselect <full-duplex>

Local Machine netstat -nr

Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default 10.10.12.1 UGSc 25 31 en1
10.10.12/24 link#5 UCS 2 0 en1
10.10.12.1 0:f:b5:b:7c:da UHLW 25 13 en1 952
10.10.12.3 0:1c:10:27:ae:25 UHLW 0 14 en1 1060
10.10.12.114 127.0.0.1 UHS 0 0 lo0
127 127.0.0.1 UCS 0 0 lo0
127.0.0.1 127.0.0.1 UH 13 44110 lo0
169.254 link#5 UCS 0 0 en1

Internet6:
Destination Gateway Flags Netif Expire
::1 link#1 UHL lo0
fe80::%lo0/64 fe80::1%lo0 Uc lo0
fe80::1%lo0 link#1 UHL lo0
fe80::%en0/64 link#4 UC en0
fe80::%en1/64 link#5 UC en1
fe80::211:24ff:fe8e:e8dc%en1 0:11:24:8e:e8:dc UHL lo0
ff01::/32 ::1 U lo0
ff02::/32 ::1 UC lo0
ff02::/32 link#4 UC en0
ff02::/32 link#5 UC en1

Server ifconfig

eth0 Link encap:Ethernet HWaddr 00:191:72:1C:C5
inet addr:10.10.12.3 Bcast:10.10.12.255 Mask:255.255.255.0
inet6 addr: fe80::219:d1ff:fe72:1cc5/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:187832 errors:0 dropped:0 overruns:0 frame:0
TX packets:129492 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:249031110 (237.4 MiB) TX bytes:31157954 (29.7 MiB)
Base address:0x30e0 Memory:5a200000-5a220000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:40 errors:0 dropped:0 overruns:0 frame:0
TX packets:40 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3253 (3.1 KiB) TX bytes:3253 (3.1 KiB)

Server netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
10.10.12.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 10.10.12.1 0.0.0.0 UG 0 0 0 eth0

[i92guboj]

I tried the crossover cable (I have a hub, but it's tough to get to).

ssh got me in right away!

Wow. Thanks!

Any ideas on how I track down the network problem? I have tried to ssh to a third local computer from both the Knoppmyth box and from my laptop. Again, long lag. No login.

In the next message, I'm posting the routing tables for my laptop and the Knoppmyth computer. Are they meaningful, now?

Thanks!

Gary

Erm, sorry if I am hitting at the obvious and stupid thing, but I have to ask it just in case: have you tried to change the wire for that box?

1.- The rest of the boxes in your network do work ok.
2.- You can ssh from or to anywhere, except that box.
3.- But that box connects ok when you used another cable.

[noob_for_life]

Erm, sorry if I am hitting at the obvious and stupid thing, but I have to ask it just in case: have you tried to change the wire for that box?

1.- The rest of the boxes in your network do work ok.
2.- You can ssh from or to anywhere, except that box.
3.- But that box connects ok when you used another cable.

Great observation. But, I don't think it's the cable. I neglected to mention this before. But, I also would try to ssh from the Myth box to a computer off of my network. That went quickly.

The problem is now fixed. I don't know why. I started fiddling with lots of stuff, purging junk on the hard drive, checking the configuration on the router, minor tweaks to my wireless network. They were little things which I thought would have no effect. But, something did. I can now connect quickly.

Thank you all for your help.

gary