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I have 5 2960 switches configured in my network. The issue I am facing is that while telnetting to the switches (eg: A) sometimes abruptly the telnet connection gets closed and repeated attempts sees the Telnet connection being refused. What I then do is telnet to another switch (B), and from there telnet to the original switch (A). That never fails.

The switches are all on one Default VLAN (192.168.1.0) and I am on a Management VLAN (192.168.40.0). Is there any correlation between different subnets and telnet? There shouldn't be as the issue is only intermittent and random.

Please advise.

Also the Line config looks like this:

line vty 0 1
 password 7 AAAAAAAAAAAAAAAAAAAAA
 login
line vty 2 4
 password 7 BBBBBBBBBBBBBBBB
 login
line vty 5 15
 login
!
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    More information required: Does the problem happen to every switch? Does the problem happen more on one switch than others? What events show up in the switch error logs during that time? EDIT: I would also like to point out that the "password 7" stuff is really, really bad. Consider changing to full use of "aaa new-model". – Panther Modern May 15 '14 at 18:08
  • It is actually happening randomly to certain switches. It does happen more on some switches than others but I have similar configurations on all of them. I shall consider using aaa authentication. I have not checked the switch error logs, I shall try later today and update any new info received. Thanks :) – gokul varma nk May 15 '14 at 21:52
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    be sure to check for duplicate IP addresses on the switched subnets... this is one possible explanation for what you're seeing. – Mike Pennington May 16 '14 at 2:31
  • How many users have access to the management interfaces on these switches? Can you post the output from "show users" on one if the problem switches? – Avery Abbott Jun 22 '14 at 5:53
  • I will definitely try to get sh users output next time it occurs. – gokul varma nk Jun 23 '14 at 7:46
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I've seen something similar when there have been duplicate IP addresses in the network. Check the ARP cache on your PC (if you're on the same network) or router and see if the MAC address changes during the problem. If it does, track the two MAC addresses down through the switch MAC address tables and configure unique IP addresses

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Increase the buffer size on the switch and log level 7 if you don't have a logging server. The other device you want to be looking at is your layer 3 since you're crossing segments.

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The sessions are not timing out. If you can get in type show session then disc 0, or whatever the session number(s) are. You should be able to configure up to 15 concurrent I think. I know it's atleast 5 (line vty 0 - 4).

enter image description here

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