Mac address flapping

Answered Question
Apr 5th, 2010
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hey

Expert i need your help.find the attached file  CAt OS 4500 version 6.3 using as core  fiber connectivtybetween access swicthes 2950


Vlan 1 is running on ial switches


CAt OS moudue 3 few user are connected   on modue 4 mostly servers are connected 


access swicthes are 2950  where only user are connected following are the error


%SYS-4-pb-WARN:1/Host 00:0b:db:c2:18:53 is flapping between 3/1 and 4/7



%SYS-4-pb-WARN:1/Host 00:0a:b7:e7:6d:80 is flapping between 3/1 and 4/7


how can i resolve thius issue


kindly help me

Attachment: 
Correct Answer by Ganesh Hariharan about 7 years 2 months ago

Thanks Ryan this is extermey helpful to me .Spantree by default on Cisco Swithc Vlan is running  accross network



load balanincg i did get can you elaborate more coz the mac address flapping  are from Active directory.ISA server ,File server


did u find anythhing wrong  in Network Diagram


Thanks again Ryan

Hi,


Check out the teaming configuration at server level,genrally they used to configure in Active/Active mode.If yes then try configure in Active/Passive mode and then check the server ports should not flap in your switches.


Hope to Help !!


Ganesh.H


Remember to rate the helpful post

I am guessing that you have the load balancing feature enabled.


If you don't need it you could just turn it off and it should resolve it, but incase you actually need to keep it on then you could configure a static IP to multicast mac address entry and turn on IGMP snooping or configure the multicast mac to the ports that are part of the load balancing group.


Another, less used solution, would be to change the mode from multicast to broadcast.  It's obviously less used because it's not viable all the time.



If you are not using load balancing then the next question is "are you using spanning trees"?


Spanning tree is actually a more common cause.  Spanning tree issues form during the learning phase and are a result of imporper "learning" of mac address'.  If you have a spanning tree issue, or think you might, then check this link out:

http://www.ciscosystems.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800951ac.shtml

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Correct Answer

I am guessing that you have the load balancing feature enabled.


If you don't need it you could just turn it off and it should resolve it, but incase you actually need to keep it on then you could configure a static IP to multicast mac address entry and turn on IGMP snooping or configure the multicast mac to the ports that are part of the load balancing group.


Another, less used solution, would be to change the mode from multicast to broadcast.  It's obviously less used because it's not viable all the time.



If you are not using load balancing then the next question is "are you using spanning trees"?


Spanning tree is actually a more common cause.  Spanning tree issues form during the learning phase and are a result of imporper "learning" of mac address'.  If you have a spanning tree issue, or think you might, then check this link out:

http://www.ciscosystems.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800951ac.shtml

Faizan Khursheed Mon, 04/05/2010 - 23:23
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Thanks Ryan this is extermey helpful to me .Spantree by default on Cisco Swithc Vlan is running  accross network



load balanincg i did get can you elaborate more coz the mac address  flapping  are from Active directory.ISA server ,File server


did u find anythhing wrong  in Network Diagram


Thanks again Ryan

Correct Answer
Ganesh Hariharan Tue, 04/06/2010 - 00:11
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  • Community Spotlight Award,

    Member's Choice, February 2016

Thanks Ryan this is extermey helpful to me .Spantree by default on Cisco Swithc Vlan is running  accross network



load balanincg i did get can you elaborate more coz the mac address flapping  are from Active directory.ISA server ,File server


did u find anythhing wrong  in Network Diagram


Thanks again Ryan

Hi,


Check out the teaming configuration at server level,genrally they used to configure in Active/Active mode.If yes then try configure in Active/Passive mode and then check the server ports should not flap in your switches.


Hope to Help !!


Ganesh.H


Remember to rate the helpful post

Faizan Khursheed Tue, 04/06/2010 - 01:58
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following is the cofiguration of Core  and Spanning tree summary


SH RUN


Console> (enable) sh run
This command shows non-default configurations only.
Use 'show config all' to show both default and non-default configurations.
...........
..................
....................
....................
....................



..


begin
!
# ***** NON-DEFAULT CONFIGURATION *****
!
!
#time: Sun Apr 4 2010, 23:51:26
!
#version 6.3(5)
!
!
#system web interface version(s)
set password $2$6mYV$gH5uk5SbZ.byhO9Hr25tV0
set enablepass $2$Gq3A$CWlLAr7fym0BqmBG7oXEO1
!
#test
!
#frame distribution method
set port channel all distribution mac both
!
#snmp
set snmp community read-only      name oup_community
set snmp trap enable  module
set snmp trap enable  chassis
set snmp trap enable  bridge
set snmp trap enable  repeater
set snmp trap enable  vtp
set snmp trap enable  auth
set snmp trap enable  ippermit
set snmp trap enable  vmps
set snmp trap enable  entity
set snmp trap enable  config
set snmp trap enable  stpx
set snmp trap enable  syslog
set snmp trap enable  system
!
#ip    
set interface sc0 1 10.46.2.5/255.255.254.0 10.46.3.255


set interface sl0 down
set interface me1 down
!
#spantree
#vlan                        
set spantree priority 8192   1
!
#syslog
set logging level cops 2 default
!
#set boot command
set boot config-register 0x2
set boot system flash bootflash:cat4000.6-3-5.bin
!
#port channel
set port channel 1/1-2 458
set port channel 2/1-2 459
set port channel 2/3-6 460
set port channel 2/7-10 461
set port channel 2/11-14 462
set port channel 2/15-18 463
set port channel 2/19-22 464
set port channel 2/23-26 465
set port channel 2/27-30 466
set port channel 2/31-34 467
set port channel 3/1-2 468
set port channel 3/3-6 469
set port channel 3/7-10 470
set port channel 3/11-14 471
set port channel 3/15-18 472
set port channel 3/19-22 473
set port channel 3/23-26 474
set port channel 3/27-30 475
set port channel 3/31-34 476
!
#module 1 : 2-port 1000BaseX Supervisor
set port trap       1/1-2  enable
set port channel 1/1-2 mode off
!
#module 2 : 34-port 10/100/1000 Ethernet
set port trap       2/1-34  enable
set spantree portfast    2/3-34 enable
set port channel 2/1-34 mode off
!      
#module 3 : 34-port 10/100/1000 Ethernet
set port trap       3/1-34  enable
set trunk 3/5  off dot1q 1-1005
set trunk 3/6  off dot1q 1-1005
set trunk 3/15 off dot1q 1-1005
set trunk 3/16 off dot1q 1-1005
set trunk 3/17 off dot1q 1-1005
set trunk 3/18 off dot1q 1-1005
set trunk 3/19 off dot1q 1-1005
set trunk 3/20 off dot1q 1-1005
set trunk 3/21 off dot1q 1-1005
set trunk 3/22 off dot1q 1-1005
set trunk 3/23 off dot1q 1-1005
set trunk 3/26 off dot1q 1-1005
set trunk 3/27 off dot1q 1-1005
set trunk 3/30 off dot1q 1-1005
set spantree portfast    3/3-34 enable
set port channel 3/1-34 mode off
!
#module 4 : 24-port 10/100/1000 Ethernet
set spantree portfast    4/1-24 enable
set spantree portvlancost 4/1  cost 3
set spantree portvlancost 4/2  cost 3
set spantree portvlancost 4/3  cost 3
set spantree portvlancost 4/4  cost 3
set spantree portvlancost 4/6  cost 3
set spantree portvlancost 4/7  cost 3
set spantree portvlancost 4/8  cost 3
set spantree portvlancost 4/10 cost 3
set spantree portvlancost 4/12 cost 3
set spantree portvlancost 4/14 cost 3
set spantree portvlancost 4/15 cost 3
set spantree portvlancost 4/17 cost 3
set spantree portvlancost 4/18 cost 3
set spantree portvlancost 4/19 cost 3
set spantree portvlancost 4/20 cost 3
set spantree portvlancost 4/21 cost 3
set spantree portvlancost 4/22 cost 3
set spantree portvlancost 4/23 cost 3
set spantree portvlancost 4/24 cost 3
!
#module 5 empty
!
#module 6 empty
!
#cam   
set cam agingtime 1    28800
end
Console> (enable)


----------------------------------------------------*****--------------------------------------------------------****----------------------------------------------------***-----------------------------------------



Console> (enable) sh spantree
VLAN 1
Spanning tree mode          PVST+
Spanning tree type          ieee
Spanning tree enabled


Designated Root             00-0b-46-26-b4-00
Designated Root Priority    8192
Designated Root Cost        0
Designated Root Port        1/0
Root Max Age   20 sec   Hello Time 2  sec   Forward Delay 15 sec


Bridge ID MAC ADDR          00-0b-46-26-b4-00
Bridge ID Priority          8192
Bridge Max Age 20 sec   Hello Time 2  sec   Forward Delay 15 sec


Port                     Vlan Port-State    Cost      Prio Portfast Channel_id
------------------------ ---- ------------- --------- ---- -------- ----------
1/1                     1    not-connected         4   32 disabled 0        
1/2                     1    not-connected         4   32 disabled 0        
2/1                     1    forwarding            4   32 disabled 0        
2/2                     1    not-connected         4   32 disabled 0        
2/3                     1    not-connected       100   32 enabled  0        
2/4                     1    not-connected       100   32 enabled  0        
2/5                     1    not-connected       100   32 enabled  0        
2/6                     1    forwarding           19   32 enabled  0        
2/7                     1    forwarding           19   32 enabled  0        
2/8                     1    forwarding           19   32 enabled  0        
2/9                     1    forwarding           19   32 enabled  0        
2/10                    1    not-connected       100   32 enabled  0        
2/11                    1    forwarding           19   32 enabled  0        
2/12                    1    forwarding           19   32 enabled  0        
2/13                    1    forwarding           19   32 enabled  0        
2/14                    1    forwarding          100   32 enabled  0        
2/15                    1    not-connected       100   32 enabled  0        
2/16                    1    not-connected       100   32 enabled  0        
2/17                    1    forwarding           19   32 enabled  0        
2/18                    1    forwarding           19   32 enabled  0        
2/19                    1    not-connected       100   32 enabled  0        
2/20                    1    not-connected       100   32 enabled  0        
2/21                    1    forwarding           19   32 enabled  0        
2/22                    1    forwarding           19   32 enabled  0        
2/23                    1    not-connected       100   32 enabled  0        
2/24                    1    forwarding          100   32 enabled  0        
2/25                    1    not-connected       100   32 enabled  0        
2/26                    1    not-connected       100   32 enabled  0        
2/27                    1    not-connected       100   32 enabled  0        
2/28                    1    forwarding           19   32 enabled  0        
2/29                    1    not-connected       100   32 enabled  0        
2/30                    1    not-connected       100   32 enabled  0        
2/31                    1    forwarding           19   32 enabled  0        
2/32                    1    not-connected       100   32 enabled  0        
2/33                    1    not-connected       100   32 enabled  0        
2/34                    1    not-connected       100   32 enabled  0        
3/1                     1    forwarding            4   32 disabled 0        
3/2                     1    not-connected         4   32 disabled 0        
3/3                     1    forwarding           19   32 enabled  0        
3/4                     1    not-connected       100   32 enabled  0        
3/5                     1    not-connected       100   32 enabled  0        
3/6                     1    not-connected       100   32 enabled  0        
3/7                     1    forwarding           19   32 enabled  0        
3/8                     1    forwarding           19   32 enabled  0        
3/9                     1    forwarding           19   32 enabled  0        
3/10                    1    forwarding           19   32 enabled  0        
3/11                    1    not-connected       100   32 enabled  0        
3/12                    1    not-connected       100   32 enabled  0        
3/13                    1    forwarding           19   32 enabled  0        
3/14                    1    forwarding           19   32 enabled  0        
3/15                    1    forwarding           19   32 enabled  0        
3/16                    1    forwarding           19   32 enabled  0        
3/17                    1    forwarding           19   32 enabled  0        
3/18                    1    forwarding           19   32 enabled  0        
3/19                    1    forwarding           19   32 enabled  0        
3/20                    1    forwarding           19   32 enabled  0        
3/21                    1    forwarding           19   32 enabled  0        
3/22                    1    forwarding           19   32 enabled  0        
3/23                    1    not-connected       100   32 enabled  0        
3/24                    1    forwarding           19   32 enabled  0        
3/25                    1    not-connected       100   32 enabled  0        
3/26                    1    forwarding           19   32 enabled  0        
3/27                    1    not-connected       100   32 enabled  0        
3/28                    1    not-connected       100   32 enabled  0        
3/29                    1    forwarding           19   32 enabled  0        
3/30                    1    not-connected       100   32 enabled  0        
3/31                    1    forwarding           19   32 enabled  0        
3/32                    1    not-connected       100   32 enabled  0        
3/33                    1    not-connected       100   32 enabled  0        
3/34                    1    not-connected       100   32 enabled  0        
4/1                     1    not-connected       100   32 enabled  0        
4/2                     1    not-connected       100   32 enabled  0        
4/3                     1    not-connected       100   32 enabled  0        
4/4                     1    not-connected       100   32 enabled  0        
4/5                     1    forwarding            4   32 enabled  0        
4/6                     1    not-connected       100   32 enabled  0        
4/7                     1    forwarding           19   32 enabled  0        
4/8                     1    forwarding           19   32 enabled  0        
4/9                     1    forwarding            4   32 enabled  0        
4/10                    1    not-connected       100   32 enabled  0        
4/11                    1    forwarding            4   32 enabled  0        
4/12                    1    not-connected       100   32 enabled  0        
4/13                    1    forwarding            4   32 enabled  0        
4/14                    1    not-connected       100   32 enabled  0        
4/15                    1    not-connected       100   32 enabled  0        
4/16                    1    forwarding            4   32 enabled  0        
4/17                    1    not-connected       100   32 enabled  0        
4/18                    1    not-connected       100   32 enabled  0        
4/19                    1    not-connected       100   32 enabled  0        
4/20                    1    not-connected       100   32 enabled  0        
4/21                    1    not-connected       100   32 enabled  0        
4/22                    1    not-connected       100   32 enabled  0        
4/23                    1    not-connected       100   32 enabled  0        
4/24                    1    not-conbnected       100   32 enabled  0        
Console> (enable)




Console> (enable) sh spantree  summary
MAC address reduction: disabled
Root switch for vlans: 1.
BPDU skewing detection disabled for the bridge
BPDU skewed for vlans:  none.
Portfast bpdu-guard disabled for bridge.
Portfast bpdu-filter disabled for bridge.
Uplinkfast disabled for bridge.
Backbonefast disabled for bridge.


Summary of connected spanning tree ports by vlan


VLAN  Blocking Listening Learning Forwarding STP Active
----- -------- --------- -------- ---------- ----------
   1         0         0        0         43         43


      Blocking Listening Learning Forwarding STP Active
----- -------- --------- -------- ---------- ----------
Total        0         0        0         43         43
Console> (enable)  bb

Ganesh Hariharan Tue, 04/06/2010 - 02:09
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  • Purple, 4500 points or more
  • Community Spotlight Award,

    Member's Choice, February 2016

Hi,


Genrally a host flapping messages from servers are due to misconfiguration at NIC level of server,As these server are connected with two NIC to two different switches or on the same switches.


If both the nic at server end is configured at active/active so will get these type of messaged at switch level,so what i would suggest check the configuration of teaming or load balancing at server level and try configure the load balancing method to active/passive.


Hope to Help !!


Ganesh.H

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