I can't remember the specifics about the network oddities on XEN unfortunately, happened years ago. A few thoughts though. Is it just ssh having issues or do all services on that server behave similarly? What can you see if you strace -f the sshd process?
The only network oddity that comes to mind right now happened under ESX where random VMs would stop being able to communicate. They could see everything else on the virtual switch fine, but anyone on a different switch inside the host or a network outside of the host was unavailable. The only thing that seemed to fix it was move the VM to a different host or a hard down and restart. On Mon, Oct 6, 2014 at 1:12 PM, Yves Dorfsman <[email protected]> wrote: > Yes, sort of. The way you do is you stop the instance, then start it, and > hope > it's going to be migrated. > > Can you tell us more about the network stack issues on XEN? Is that a > recent > issue? I had never seen this before the great september reboot... > > On 2014-10-06 12:06, Jared Moore wrote: > > Not super familiar with AWS, but can you move instances to a new > hypervisor? > > I've seen similar issues with VMware and XEN where the network stack at > the > > hypervisor gets a bit goofed up and moving the VM to a different > hypervisor > > fixes the issue. Rather than stop/start and get a new IP if you can keep > the > > IP, but move the instance somewhere and the problem goes away that would > be > > quite telling. > > > > On Mon, Oct 6, 2014 at 11:41 AM, Yves Dorfsman <[email protected] > > <mailto:[email protected]>> wrote: > > > > > > We've run into this weird AWS issue 3 times now in a week, never > seen it > > before: > > > > A Linux instance becomes unreachable via ssh from some ip addresses. > If you > > try to ssh from those addresses, it just hangs, for ever, until to > ctrl-c out > > of it. Yet you can ssh from other ip addresses without any problem. > > > > The ip addresses that work and that don't seem random, some are > outside AWS, > > some inside, even on the same subnet. When we run in DEBUG3 mode, we > see that > > the client sent it's key, while the server waits for the said key, > and sits > > there waiting. The few similar issues (ssh hanging at key exchange) > we found > > when googling were solved by changing MTU! > > > > The only resolution we have found so far is to stop/start the > instance and get > > a new ip (tbh, we haven't tried to just reboot). > > > > Has anybody run into this? Any idea what's going on? > > > > -- > > Yves. > >
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