Cisco Switchport gets into err-disabled state when connected to a HP switch.

[Talha Abbasi]

Hello all... I've recently been assigned a task to provide connectivity to a small elementary school.  I'm running into an issue and would appreciate advice/suggestions:

1. Linksys E2500 router acting as DHCP (and connected to modem provided by Optimum)
2. Static Public IP assigned to router
3. Internal LAN scheme is 192.168.1.x
4. Online connectivity is OK and working fine when directly connected via hardwire to Linksys router (or via wifi)
5. Ethernet 1 port (on Linksys) connect to Cisco 3550 fa0/24 (switch has basic configuration, no VLANS, all ports are on default VLAN1)
6. HP switch connected to Cisco 3550 port fa0/23
7. Netgear switch connected to HP switch port fa0/48

The issue is that when I connect the HP switch with the CIsco swith..... fa0/24 (on Cisco 3550) goes into err-disabled state, and i've to do a shut/no-shut to bring it back up.

I then decided to individually connect all three switches with the Linksys router (and not connect the switches with each other), but encountered the same issue, where port fa0/24 on the Cisco switch shuts down and goes into err-disable state.

Any ideas as to what could be causing this?  Is it BDPU guard acting up?

Thanks for reading.

/regards

[mahesh18]

Hi Talha,

Yes seems it is BPDU guard  configured on cisco switch.

You need to disable that if you want it to make work with HP switch

Regards

MAhesh

[Talha Abbasi]

Hi Mahesh,

Please note that all switchports on the Cisco switch do not have any specific configuration assigned to them.  The config is pretty basic/factory default.  Only things configured on the switch are:

1. static IP assigned to vlan 1
2. default gateway
3. enable password
4. line con 0 password
5. line vty 0 4 password
6. vtp mode set to transparent
7. ...and that is it.

nothing else done on this Cisco switch. 

Is the BDPU guard configured automatically on these 3550s?

Regards.

[Rasika Nayanajith]

If you look at "show logg | in err " you should be able to see the log entry for the switch port going down. That will give you an idication why port is going to error-disabled

SW# sh logg | in err

Syslog logging: enabled (0 messages dropped, 0 messages rate-limited, 0 flushes, 0 overruns, xml disabled, filtering disabled)

Sep 16 12:44:03 AEST: %PM-4-ERR_DISABLE: bpduguard error detected on Gi1/0/1, putting Gi1/0/1 in err-disable state

Also following command will also help you to troubleshoot

SW#show errdisable recovery

ErrDisable Reason            Timer Status

-----------------            --------------

arp-inspection               Disabled

bpduguard                    Enabled

channel-misconfig (STP)      Enabled

dhcp-rate-limit              Disabled

dtp-flap                     Disabled

gbic-invalid                 Disabled

inline-power                 Disabled

l2ptguard                    Disabled

link-flap                    Enabled

mac-limit                    Disabled

loopback                     Enabled

pagp-flap                    Disabled

port-mode-failure            Disabled

pppoe-ia-rate-limit          Disabled

psecure-violation            Enabled

security-violation           Enabled

sfp-config-mismatch          Disabled

small-frame                  Disabled

storm-control                Enabled

udld                         Enabled

vmps                         Disabled

psp                          Disabled

Timer interval: 60 seconds

Interfaces that will be enabled at the next timeout:

Interface       Errdisable reason       Time left(sec)

---------       -----------------       --------------

Gi1/0/1                bpduguard           40

HTH

Rasika

[Leo Laohoo]

Immediately after the port goes into err-disable, post the output to the command "sh interface status err".