On Thu, Apr 23, 2009 at 11:22:34AM +1000, Cameron Simpson wrote:
On 22Apr2009 17:51, Dave Feustel <dfeustel(a)mindspring.com>
wrote:
| On Wed, Apr 22, 2009 at 05:08:15PM -0430, Patrick O'Callaghan wrote:
| > On Wed, 2009-04-22 at 17:16 -0400, Dave Feustel wrote:
| > > After getting ssh to work, I altered the ip addresses of my computers.
| >
| > How? What exactly did you do? Are these addresses static or assigned by
| > a DHCP server?
|
| All my local net addresses are assigned by dhcpd running on the
| firewall.
|
| > > Now ssh doesn't work and neither does ping, apparently (in the case of
| > > ping) because my switch doesn't forget ip addresses even after poweroff.
| >
| > Why do you think there's a problem with ssh if you can't use ping? In
| > most cases if ping doesn't work, nothing works, assuming pings aren't
| > being filtered on the way to or from the target. "traceroute
<target>"
| > can be helpful here.
|
| The problem with ping was a result of my switch getting confused after
| I changed the ip addresses. I've gotten everything working again by
| going back to the original address assignment and removing power from
| the switch to make the switch forget address-port associations.
It may not be the switch. If the two machines are on the same network,
the machines' own ARP tables will remember the old IP<->MAC mapping,
though that should time out and refresh after about 30s. Unless the
switch is doing layer 3 switching (direct IP based routing instead of
MAC based routing).
Everything seems to be working wrt the switch now. The problem I am now
trying to resolve is why the initial windows load via ssh of XMaple
takes 1 minute 38 seconds. Every complete repaint of the XMaple window takes
approximately the same amount of time. This makes using X11 to run
Maple an agonizingly slow process - too slow to put up with.
| So does a change of IP address for an ssh target affect the way ssh
works?
|
| > You might also try "arp" to see if the IP<->MAC mapping is
correct.
"arp -an" is the fast incantion to test.
-------------------
2/home/daf}arp -an
? (192.168.6.1) at 00:22:3f:db:f3:90 [ether] on eth0
2/home/daf}ssh -l daf $C4a
The authenticity of host '192.168.6.32 (192.168.6.32)' can't be
established.
RSA key fingerprint is af:6e:39:4a:4f:15:0d:ed:c9:01:06:e5:11:60:66:1c.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.6.32' (RSA) to the list of known
hosts.
Password:
Last login: Tue Apr 21 12:57:12 2009 from 192.168.3.1
motd
2/home/daf}echo $C4a
192.168.6.32
2/home/daf}
------------------
Note that the ssh session terminated immediately after the successful
login. This has happened several times this afternoon and I have no
idea why.
Ssh keeps a ~/.ssh/known_hosts file that logs host keys and IP
addresses
and host names in order to detect when things change (i.e. to check if
an imposter has arrived).
I deleted the known_hosts file to get rid of the entries with obsolete
ip addresses.
We would need to see the output of "ssh -v .....", but you
should fix
ping first. If ping doesn't work, ssh almost certainly won't, and for
reasons having nothing to do with ssh itself.
Ping works fine now. Ssh works. It's just way too slow running XMaple.