OK, Here's another one for you experts out there. We've got a 24 port hub/switch in telehouse which is connected to a router. We've got several machines connected up and they are running great. No problems. Excellent connectivity. One of our guys goes down to London yesterday and swops a network card in one of the boxes and installs a fresh new RedHat box in the cabinet for us to play with. Things start to go weird.. The box with the new network card in it and the totally new box can see all the other machines on the subnet and they can see each other. Fine up to now. So.. I try to telnet into these boxes from home (NTL dialup modem) and can't access them. I can access all the other machines on that subnet no problem but not those two machines. In addition, those two machines can't see the router that's attached to the hub. I'm running no clever firewalling or anything on any of those machines. My thoughts are that the switch is misbehaving and is about to smoke or that the router is selectively ignoring certain addresses... Any other thoughts on this? Cheers. Mark W.
On Sat, Apr 21, 2001 at 03:18:08PM +0100, Mark Wilkinson wrote about network problems at Telehouse. Mark,
Steve Fosdick wrote:
On Sat, Apr 21, 2001 at 03:18:08PM +0100, Mark Wilkinson wrote about network problems at Telehouse.
Mark,
From your initial description my first reaction was that the default route on the two new boxes may not be correct, but that doesn't explain the boxes concerned not being able to see the router direct.
this would have been my hunch as well.. check the default route and/or subnet masks... Sz -- Open source solutions at http://www.entora.co.uk/
Mark Wilkinson wrote:
I try to telnet into these boxes from home (NTL dialup modem) and can't access them. I can access all the other machines on that subnet no problem but not those two machines. Don't use telnet, do use ssh :-)
Can you ping the new machines from other machines on that subnet? or even better login to them? can you see them if you run tcpdump or ethereal? arpwatch may also help here.
In addition, those two machines can't see the router that's attached to the hub. I presume you can do the above then but can't ping the router, again what happens while running tcpdump? do these machines have the correct subnet masks? what do their routing tables look like? what happens if you try a traceroute to your router? and have you checked the interface statistics?
I'm running no clever firewalling or anything on any of those machines. Are you sure this is correct? is there any firewalling on the router?
My thoughts are that the switch is misbehaving and is about to smoke or that the router is selectively ignoring certain addresses... Possibly, but like Steve said it is more likely human error with a working machine suddenly not working and a new one not working. It seems likely that your tech made the same mistake twice!
If you still are having trouble later you can mail me off list if it is more appropriate. Adam PS sorry about the earlier mail coming from the future, damn M$ changing my clock for me again! PPS if this sounds like another post I just made I'm sorry but I didn't see the original turn up and netscape crashed just around when I sent it. -- Adam Bower, <abower@zeus.com> Tel: +44 1223 525000 System Administrator Fax: +44 1223 525100 Zeus Technology Ltd http://www.zeus.com Zeus House, Cowley Road Cambridge CB4 0ZT England
participants (4)
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Adam Bower -
Mark Wilkinson -
Neill Newman -
Steve Fosdick