Recently some of our users have complained that their sessions to our IBM AS400 drop their connection during the first hour or two of the work day, 8am-10am. This is a very small group of users, maybe a dozen out of 200 hundred plus. Everyone else seems to be working okay, but we have also received reports that streaming video for some users stutters along. And event logs for the affected AS400 users show that outlook loses connection to the exchange server for a few seconds.
Using Wireshark I can see that the typical DHCP process (discovery, request, offer, ack) repeats many times for users, typically a dozen times. This morning I did an ipconfig release then renew on my computer to start off the DHCP conversation and it repeated 11 times. In two of the eleven, I did notice the ACK to the previous request came in after the next discovery. But the original few four part DHCP conversation was in perfect order.
I also did notice that the original four part conversation had a lease time of one minute. But the second four part conversation had the correct lease time as set on our MS DHCP servers. Perhaps this was because my IP address (which is reserved) hadn't cleared in some table? We have two DHCP servers. Total speculation on my part.
But I also noticed that some users have a series of repeated DHCP conversations for minutes. One went for at least 20 minutes this morning when that person added a new computer to the domain.
The two DHCP servers are on the server vlan, and the users are on the user vlan. Two helper addresses are part of the vlan config.
I did several Google searches and couldn't really find anything that described this behavior. Most spoke to one end of the conversation not receiving or acknowledging part of the conversation, but that's not the case for us. The conversation completes but then repeats, over and over.
Where should I look in the capture, or on the network do determine possible solutions?
Thank you, Garry
Thanks, Garry