Err-disable & Load Balancing

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Sep 23rd, 2010
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Hi Experts,

1) What are the main reasons for "err-disable"  on Switch GigabitEthernet or Fastethernet ports.

2) What are the key difference between Load Balancing protocols  HSRP, VRRP, GLBP infact all these perform the same function.Other way want to clear what r the points and feature to decide that particular protocol (out of these three) need to use at particular network or can say scenerio.

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matrix lin Thu, 09/23/2010 - 20:16
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1) What are the main reasons for "err-disable"  on Switch GigabitEthernet or Fastethernet ports.

Err-disable can be caused by below reasons.The mostly reason is that user connects additional network device like HUB or Switch for the network port extending or 1 cable connected to 2 ports in the same switch,the port will be auto disabled for security and the interval time can be set.

errdisable recovery cause udld
errdisable recovery cause bpduguard
errdisable recovery cause security-violation
errdisable recovery cause channel-misconfig
errdisable recovery cause pagp-flap
errdisable recovery cause dtp-flap
errdisable recovery cause link-flap
errdisable recovery cause sfp-config-mismatch
errdisable recovery cause gbic-invalid
errdisable recovery cause psecure-violation
errdisable recovery cause port-mode-failure
errdisable recovery cause dhcp-rate-limit
errdisable recovery cause mac-limit
errdisable recovery cause vmps
errdisable recovery cause storm-control
errdisable recovery cause inline-power
errdisable recovery cause loopback
errdisable recovery cause small-frame
errdisable recovery interval 30

Mahesh Gohil Fri, 09/24/2010 - 22:58
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HSRP/GLBP is cisco proprietry protocol while VRRP is open standard protocol and substitute for HSRP. HSRP and VRRP ia having same

functionality. but GLBP differes especially in load balancing.

ex: If you have 10pc and 2 router and your requirement is load sharing between two router then

     # create two hsrp groups on router one is backup of other on one router and vice versa

    # configure half of the PC with gateway as standby IP of first hsrp group and

   # configure other half of PCs with gateway as standby of second hsrp group.

while in GLBP you can configure in such a way that traffic from LAN clients can be shared by multiple routers, thereby sharing the traffic load more equitably among available routers.

please go through below link for GLBP functionality it is very interesting


Mahesh Tue, 09/28/2010 - 11:04
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Txns Mahesh,

For Err-disable querry i am looking for more specific answer. As i read somewhere that reason for err-disable is anyway depend on the no. of high BPDU packets on that ports (i am not sure whether i am re-calling this correct or not). and need your help in better understanding for reason.

aminulnt Tue, 09/28/2010 - 11:51
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First of all if you configured port security then when a violation is detected, the switch automatically places the port in the "err-disabled" shutdown state.

Switch# show interface f0/1

FastEthernet0/1 is down, line protocol is down (err-disabled)

Switch(config)# errdisable recovery cause psecure-violation

Switch(config)# errdisable recovery interval 300

The above configuration enables auto recovery for port security violations after five minutes. As evident in the list, auto recovery can apply to far more than just port security violations.You can also shut and no shut.

Switch# show err disable recovery

Aminul Wed, 09/29/2010 - 10:46
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Txns Aminul,

But here i am again clearing my querry, I already aware about the Violation on port which cause port in err-disable.But i am looking for the cause of occuring that vioalation  , simply wht are the reason that cause vioaltion to occur on port..may be this time clear to you.


Mahesh Gohil Thu, 09/30/2010 - 00:51
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This is what replied in earlier post. below are the causes of moving port from working to err-disable


Like if you give loop then your port will go in err-disable state.

Hope this is what u mean to ask. If not you can rephrase the question with some more detail




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