Dear All, I have being scratching my head over this issue for two days now so I am soliciting help from numerous ISP and network engineers who are luring on this list.
I upgraded all machines on my home network to predrag@oko$ uname -a OpenBSD oko.bagdala2.net 6.0 GENERIC.MP#0 amd64 on September 2 and a day latter I started having a very strange issue connecting to my employer network (Carnegie Mellon University 128.2.0.0/16) Namely on three random days since September 2 I could not ssh nor see the web content on any of CMU machines for several hours at the time. My fist suspect was my own DNS. I run my own Unbound cashing DNS. Sure enough I could not dig any of CMU machines except the one for which I hold A record (actually EasyDNS is doing it for me). So I switched off my own DNS at home and started using Google and OpenDNS DNS server and shure enough I could dig all CMU machines including the one for which I don't hold DNS records. However I still could not ping them even with a correct IPv4 address. At this point I concur that I didn't run traceroute but I tried something else that made me believe that it might not be problem with my own network. Namely I logged to my devio.us and freeshell.org shell accounts. I was able to ping CMU machines and my home network. I was able from devio.us and freeshell.org to dig my work machines. I was also able to ssh to them. Great. Now I tried to ping from my CMU computers my home network with the correct IPv4 address and I was not getting respond. No my firewall is not a problem. I am letting ping in and I was able all that time to ping from devio.us and freeshell.org. At this point I was truly stamped. It almost felt that either CMU was blocking my home IP address or my ISP was blocking CMU addresses possibly due to DoS attack). I have not tried reseting DHCP lease on my home network to see if I would do better with a different IP from my ISP. Note also that IPv6 is turned off on my home and at work. At this point as somebody who has never dealt with more serious things like BGPD and who don't really understand how ISP business works I am running out of ideas with the exception of traceroute which I will run if I lose ssh connection again (right now is working perfectly and I am using my own DNS server again). Thanks for the help. Predrag P.S. Oh yes I tired flashing my own DNS and fetching new root.key file but was not helpfull.
