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when the client roaming from one switch to other switch service down

Publication Date:  2018-02-27 Views:  87 Downloads:  0
Issue Description

version information : v200r010 S6720EI

networking topology 


when the cilent roaming from AP1 to AP 2 the service down packet lost ,after some time the service recovery.

the gateway is on the core switch.


Handling Process

1.check the forward mode , the AC use the direct mode. so the traffic will go to the core switch directly

2. enable the trace on the AC, the user is not offline

3. check the switch arp table and find the arp table is not refresh when the user move to AP2

before the client arp learn in the xg0/0/14

[S6720-CORE]dis arp interface Vlanif 20

IP ADDRESS      MAC ADDRESS     EXPIRE(M) TYPE        INTERFACE   VPN-INSTANCE 

                                          VLAN/CEVLAN 

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

172.19.20.254   5860-5f63-ffc6            I -         Vlanif20

172.19.20.250   a493-4cfb-794f  12        D-0         Eth-Trunk4

                                            20/-

172.19.20.52    0017-23af-aeae  18        D-0         Eth-Trunk4

                                            20/-

172.19.20.72    0017-23fa-fb9f  17        D-0         Eth-Trunk4

                                            20/-

172.19.20.89    0017-23a8-9e34  20        D-0         XGE0/0/14


after the client move to ap2 the arp is not refresh. so the packet lost  and we find the mac already learn in the new port 

[S6720-CORE]dis mac-ad | in 9e34       

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

MAC Address    VLAN/VSI                          Learned-From        Type      

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

0017-23a8-9e34 20/-                              Eth-Trunk30         dynamic  


Root Cause

the ARP is not refresh in time , when the client roaming will not send the arp packet only wait the client send the arp packet .so the service down the packet lost

Solution

in the core switch we can configure the "mac-address update arp " when the mac-address is refresh the arp will be update . the customer test the command it can work fine.


when the mac-addaree is update the arp is update too.

[S6720-CORE]dis arp interface Vlanif 20

IP ADDRESS      MAC ADDRESS     EXPIRE(M) TYPE        INTERFACE   VPN-INSTANCE 

                                          VLAN/CEVLAN 

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

172.19.20.254   5860-5f63-ffc6            I -         Vlanif20

172.19.20.250   a493-4cfb-794f  16        D-0         Eth-Trunk4

                                            20/-

172.19.20.52    0017-23af-aeae  12        D-0         Eth-Trunk4

                                            20/-

172.19.20.72    0017-23fa-fb9f  1         D-0         Eth-Trunk4

                                            20/-

172.19.20.89    0017-23a8-9e34  20        D-0         Eth-Trunk30

END