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Odd application disconnects - Vendor points to network

We have been troubleshooting an odd issue on our network for sometime and have not found the root cause. We have a software package that loses connection from the client to the server. It seems to happen to different people at different times. We have a pretty flat network that we are going to be redoing as soon as our datacenter is redesign for power, etc. Right now all clients pass through vlan 100 at our main site and our remote sites. Some servers are in vlan 100 and some vlan168. we have aprox 2,000 clients and many servers. I am wondering if the root of the problem could be vlan 100 and having way too much in it. Here is a sample output of vlan 100 on our 6509 with a sup1a.Let me know if you have any ideas or need more info.

Vlan100 is up, line protocol is up

Hardware is Cat6k RP Virtual Ethernet, address is 0007.eb5b.6342 (bia 0007.eb5b.6342)

Description: legacy vlan

Internet address is

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output never, output hang never

Last clearing of "show interface" counters 00:31:43

Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 22000 bits/sec, 26 packets/sec

5 minute output rate 13000 bits/sec, 4 packets/sec

51198 packets input, 5377200 bytes, 0 no buffer

Received 49680 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

11812 packets output, 3615802 bytes, 0 underruns

0 output errors, 0 interface resets

0 output buffer failures, 0 output buffers swapped out


Re: Odd application disconnects - Vendor points to network

Need more information. What is the layer 1,2,3 path of the client to the server? When you say "loses the connection" what is reporting the connection loss first? The client or the server?

I just finished troubleshooting a similar issue with a VPN over 3G connection. I won't go into the details, but it took some good debugs/logs on the end devices to really see what was going on. I would suggest the same approach in your situation and see which end is "dropping" the connection first.