ssh question

Dazed_75 lthielster at gmail.com
Sat Jun 18 16:08:14 MST 2011 

Supplemental information.  I have now done this in two locations (home and
at UAT) using 3 machines in each location (lapdog2 in both) and different
routers in each.  I can ssh from lapdog2 to any other with one exception
(see next paragraph).  I can also ssh from other machine to any other except
lapdog2 and the same exception.

The exception is damselfish which is a netbook running ubuntu 11.04 like
lapdog2 (a laptop).  Ubuntu 11.04 does not seem to be the common thread as
hammerhead works both ways and it is a desktop running 11.04.  Its hard to
imaging laptops being the common thread but ...

On Sat, Jun 18, 2011 at 1:02 PM, Joseph Sinclair
<plug-discussion at stcaz.net>wrote:

> Based on what you're seeing below, I'd suggest looking at the IP setup on
> the machines and any router/gateway between the two machines.
> It looks like something is allowing the ICMP traffic but blocking or
> loosing the TCP connect for port 22.
>
> It might help to run the following commands on each machine to look for
> inconsistencies or errors:
> ifconfig -a
> ip addr list
> ip neigh
> ip route
>

larry at lapdog2:~$ ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:16:36:e6:1b:b9
          inet addr:192.168.2.124  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::216:36ff:fee6:1bb9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4187 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4369 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1349793 (1.3 MB)  TX bytes:621589 (621.5 KB)
          Interrupt:18 Memory:da000000-da020000

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:12 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:720 (720.0 B)  TX bytes:720 (720.0 B)

wlan0     Link encap:Ethernet  HWaddr 00:19:d2:37:3c:33
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

larry at lapdog2:~$ ip addr list
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state
UP qlen 1000
    link/ether 00:16:36:e6:1b:b9 brd ff:ff:ff:ff:ff:ff
    inet 192.168.2.124/24 brd 192.168.2.255 scope global eth0
    inet6 fe80::216:36ff:fee6:1bb9/64 scope link
       valid_lft forever preferred_lft forever
3: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 00:19:d2:37:3c:33 brd ff:ff:ff:ff:ff:ff
larry at lapdog2:~$ ip neigh
192.168.2.1 dev eth0 lladdr 00:18:f8:3e:19:c1 REACHABLE
larry at lapdog2:~$ ip route
192.168.2.0/24 dev eth0  proto kernel  scope link  src 192.168.2.124  metric
1
169.254.0.0/16 dev eth0  scope link  metric 1000
default via 192.168.2.1 dev eth0  proto static
larry at lapdog2:~$

>
> Some *possible* causes:
> 1) More than one machine thinks it has IP 192.168.2.124 and there is an ARP
> conflict.



> Verified not true
>


> 2) You have VLAN's setup on the router and the tagging is off or the router
> isn't passing TCP traffic between the VLAN's.
>

No VLANs


> 3) The two machines have subnet masks that make them think they're on
> different networks (e.g. 255.255.255.0 and 255.255.255.252 or /24 and /30)
>

All subnet masks are 255.255.255.0

>
> If the machines are DHCP, have both release and renew their lease (and make
> sure there's only one DHCP server on the network!).
>

Verified only one dhcp server


> If they're static configured, check /etc/network/interfaces and make sure
> the subnet mask is the same on both.
>

Only one machine (fogtest) is staticly configured )on both routers) as a
static IP issued by DHCP


> Dig through your router configuration (I assume you only have one router,
> if not temporarily remove all but one router) to make sure you don't have
> VLAN's setup or that they're properly configured
>

Only one router in each loaction and they seem correct


> Check the ARP tables on the machines and the router ("ip neigh" at the
> command line on each machine, router depends on it's interface) to make sure
> you don't have duplicates and the MAC address matches for each IP address on
> the different machines
>

I'll have to research how to do that.


> example (you may see many more entries than this) (Note that 10.23.124.104
> is visible on both and the MAC value matches):
> Machine 1
> 10.23.124.104 dev eth0 lladdr 02:49:5a:9e:e2:6c STALE
> 10.23.124.123 dev eth0 lladdr 03:1d:7f:7f:4d:2d STALE
>
> Machine 2
> 10.23.124.104 dev eth0 lladdr 02:49:5a:9e:e2:6c STALE
> 10.23.124.125 dev eth0 lladdr 03:1e:4f:73:29:10 STALE
>
> There should be only one entry for each IP address in the list on each
> machine; for a given IP address, all machines should see the same MAC
> address.
>
> Hopefully that helps.  Inconsistent network issues like this are always
> difficult to track down.
>
> <<SNIPSNIPSNIP>>
> > Again, name/ip resolution is not a problem and is always working
> correctly.
> > BTW, here is an attempt from today:
> > larry at fogtest:~$ ssh -v lapdog2
> > OpenSSH_5.3p1 Debian-3ubuntu6, OpenSSL 0.9.8k 25 Mar 2009
> > debug1: Reading configuration data /etc/ssh/ssh_config
> > debug1: Applying options for *
> > debug1: Connecting to lapdog2 [192.168.2.124] port 22.
> > debug1: connect to address 192.168.2.124 port 22: Connection timed out
> > ssh: connect to host lapdog2 port 22: Connection timed out
> > larry at fogtest:~$ ping -c 3 lapdog2
> > PING lapdog2 (192.168.2.124) 56(84) bytes of data.
> > 64 bytes from lapdog2 (192.168.2.124): icmp_seq=1 ttl=64 time=0.587 ms
> > 64 bytes from lapdog2 (192.168.2.124): icmp_seq=2 ttl=64 time=0.856 ms
> > 64 bytes from lapdog2 (192.168.2.124): icmp_seq=3 ttl=64 time=0.996 ms
> >
> > --- lapdog2 ping statistics ---
> > 3 packets transmitted, 3 received, 0% packet loss, time 2002ms
> > rtt min/avg/max/mdev = 0.587/0.813/0.996/0.169 ms
> > larry at fogtest:~$
> >
> > Clearly the issue seems to be what is blocking communication to port 22
> even
> > though sshd is listening on it, iptables seems to allow it and ufw was
> > disabled yesterday and being enabled today seems to change nothing.
> >
> <<SNIPSNIPSNIP>>
>
>
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-- 
Dazed_75 a.k.a. Larry

The spirit of resistance to government is so valuable on certain occasions,
that I wish it always to be kept alive.
  - Thomas Jefferson
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