Unreasonable configuration of DHCP cause STA can't get the ip

Created: Apr 13, 2018 15:40:40Latest reply: Apr 16, 2018 16:56:23 876 2 1 0
 Fault Type Service  >> WLAN  >> STA Online Failure                                                                       
Issue
The scenario is in certain area, there are a lotof users connected to indoor AP. Average 17 STA per AP. Each users have basedspeed 5M. And there are peak hour, some of the users hard to get connected andneed to wait non-peak hour ( e.g. 4am) to get connected and do download things.


Topology is:

S12700V2R10---S5720EIV2R7---S5700LIV2R6---APV2R7C10---STA     
Alarm InformationA large numberof wireless users cant receive an IP address by DHCP
 

                                                                                                       
Handling
Process
1 Customer user the DHCP servers, we check the ip pool find the there have many free address.
2 Trace both from the switch and the ap find dhcp packtes drop random
3 Check the accress switch configuration,found there have command of dhcp snooping.
4 Check the accress switch dhcp snooping table found DHCP snoopingbinding table is exhausted in the access switch


<ACCESS_SWITCH_01>display dhcp snooping               
DHCP snoopingglobal running information :
DHCPv4snooping                         : Enable  
DHCPv6snooping                         : Enable  
Static user maxnumber                  :256    
Current staticusernumber              : 0       
Dhcp user maxnumber                    : 256      (default)
Current dhcp usernumber                : 256    
Arp dhcp-snoopingdetect                : Disable  (default)
Alarmthreshold                         : 100      (default)
Checkdhcp-rate                         : Disable  (default)
Dhcp-ratelimit(pps)                    : 100      (default)
Alarmdhcp-rate                         : Disable  (default)
Alarm dhcp-ratethreshold               : 100      (default)
Discarded dhcp packetsfor rate limit    : 0      
Bind-tableautosave                     : Disable  (default)
Offline removemac-address              : Disable  (default)
Client positiontransfer allowed         :Enable   (default)
 
DHCP snooping runninginformation for interface GigabitEthernet0/0/1 :
DHCPsnooping                           : Enable  
Trustedinterface                       : No     
Dhcp user maxnumber                    :256      (default)
Current dhcp and nduser number          :15     
Checkdhcp-giaddr                       : Disable  (default)
Checkdhcp-chaddr                       : Disable  (default)
Alarmdhcp-chaddr                       : Disable  (default)                                                       
Root Cause
DHCP snooping binding table is exhausted in the access switch                                     
Solution
Configuration the command“dhcp snooping enable no-user-binding”from the all of the access switch                                                                                                   
SuggestionsFor WLAN users not need configuration the dhcp snooping from the access switch, because from the AP already enable this.
This post was last edited by 亦花臣 at 2018-04-17 08:59.
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wissal     Created Apr 13, 2018 18:46:00 Helpful(0) Helpful(0)

useful document, thanks
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Jamalb     Created Apr 16, 2018 16:56:23 Helpful(0) Helpful(0)

So if we apply the solution:


Configuration the command “dhcp snooping enable no-user-binding” from the all of the access switch
the problem will disappear permanently? :)
  • x
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Jbattikh

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