Intermittent SSH/Telent issue to CISCO

DevilWAHDevilWAH Member Posts: 2,997 ■■■■■■■■□□
Hi,

I have this same issue on 2 X 3650C switches.

The config for the VTY lines is identical across all my devices, very basic, using local login and a username / password with privilege 15 access.

I can ping the management address and run SNMP commands to the devices. But since upgrading the IOS 99% of the time I can't get a SSH connections going. I know there are no ACL configured on the switches, and it only happens on two that are running 15.1(1). PAcket capture shows that the switch never replies to the first SYN packet of the TCP stream.

Strange this is that if I reboot the switch SSH will work once. but after that it stops and I can't connect again. I have looked using SNMP and all the VTY lines are free. The real issue is that these switches are in a high bio security building so getting to them is a nightmare. And tonight they jsut wont let me in icon_sad.gif all I want to do is log in and reboot them back to IOS 12 which was working fine.

Just strange the intermittent nature of it, definitely not duplicate IP's.
  • If you can't explain it simply, you don't understand it well enough. Albert Einstein
  • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.

Comments

  • networker050184networker050184 Mod Posts: 11,962 Mod
    A bug in your version perhaps?
    An expert is a man who has made all the mistakes which can be made.
  • pevangelpevangel Member Posts: 342
    Memory issues? Have you opened a TAC case?
  • phoeneousphoeneous Go ping yourself... Member Posts: 2,333 ■■■■■■■□□□
    Which ios version?

    Which version of ssh?

    What happens when you telnet?

    What does the log say?

    Have you enabled any debugs?
  • DevilWAHDevilWAH Member Posts: 2,997 ■■■■■■■■□□
    A bug in your version perhaps?

    I think this is what it is.

    What is particularly annoying is that to get to the switch requires 2 showers and a 3 day quarantine period! that and I can't take in a laptop, or if I do its never coming out!

    In the end I realised that after a reboot it will work for one log in if you do it straight away, but leave it 5 minutes or log out and you are stuck again.

    Annoyingly the switches do not be default allow reboot via SNMP, so have to pull the configs down, update the snmp settings, then push them back so I could remotely kick of a reload.
    Pull config 
    
    snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.2.335 i 1snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.3.335 i 4
    snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.4.335 i 1
    snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.5.335 a 192.168.1.46
    snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.6.335 s 3560inside
    snmpset -c prvtcommunity -v 2c 172.18.48.56 1.3.6.1.4.1.9.9.96.1.1.1.1.14.335 i 1
    
    
    push config
    
    
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.2.337 i 1
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.3.337 i 1
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.4.337 i 4
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.5.337 a 192.168.1.46
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.6.337 s 3560inside
    snmpset -c prvtcommunity -v 2c 172.18.48.56  1.3.6.1.4.1.9.9.96.1.1.1.1.14.337 i 1
    
    
    The last oid element (337,335) is a random number to create a table entry, this will time out after 5min or once completed.
    
    
    and
    snmpset -v2c -c prvtcommunity 172.18.48.56 .1.3.6.1.4.1.9.2.9.9.0 i 2
    (will reboot the device)
    

    Once I could log in once, I still ahve the old ISO (version12) on the boxes so just updated the boot variable and reloaded once again. I could not find a way to set the boot variable via SNMP as its no longer part of the running config. Always fun to play with a bit of CLI SNMP though :)
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
  • DevilWAHDevilWAH Member Posts: 2,997 ■■■■■■■■□□
    pevangel wrote: »
    Memory issues? Have you opened a TAC case?

    A TAC case?? when I could be having such fun working it out my self :)

    When things need to be fixed ASAP then I raise a TAC, but with this it was not affecting users so learn more by working it out myself.
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
  • pevangelpevangel Member Posts: 342
    Working it out yourself by asking a forum for help? icon_lol.gif

    I'm just messing with you. I know exactly what you mean.

    Have you considered that it might be a memory issue? I had an issue somewhat similar to yours and it was due to a memory leak.
  • DevilWAHDevilWAH Member Posts: 2,997 ■■■■■■■■□□
    What I know is that its a bug in that IOS version, or at least it seems to be. Put on version 15.1(1) and I get the isseue, revert to 12.2 and it goes away :)

    Frustratingly all these models of switches are in side high bio-security which makes testing tough. I want to upgrade them so my 802.1x config is consistent across site. but going to have to be very careful with this one.
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
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