Hello my friends,
You may notice I am omitting brand names, OS and IP addresses to make things clearer. I suppose the omitted info is irrelevant to the issue.
I have a hosted backup server at an ISP datacenter, and a routed client LAN that backups to that hosted app. We suddenly realized that backup was abysmally slow; with total uploads of 30MB/day (!) while typical uploads were on the range of 4-5 GB/day until 1/1/2014.
Initial checking showed us that only this particular PC within the LAN is failing to reach a few SPECIFIC WAN IPs located within the client's ISP boundaries, one of them being my backup server. The same destination can be reached normally from all other PCs at the LAN.
Wiresharking the ethernet interface on the problem PC eventually gives ICMP 82 (destination address prohibited) but I am none the wiser knowing this... Capture attached ! Packets are being sent over the wire on bursts of a few packets, wait a few seconds, again a few packets, and again a few seconds wait, and then ICMP 82 breaks loose.
I am assuming that the problem lies in the PC's TCP software, as all other destinations are unaffected on this partiicular PC. There are no viruses, and windows firewall on the PC has been reset. Tomorrow I will go to the client and try several methods such as winsock reset, change PC IP, reset the router, use another router....
Whatever happens, I am still stumped. What really is going on with this PC ? Where do I check next ?
Thank you for any insight !!!
PS: Please realize that the checksum error due to TCP offloading happens in ALL packets being issued from this PC. The problem is the throttling that occurs from this PC only to a few specific destinations.
