customer getting illegal ip from illegal DHCP Server

Publication Date:  2014-06-24 Views:  308 Downloads:  0
Issue Description
Customer PC start getting illegal ip addresses from some illegal DHCP server instead of original DHCP server.
Alarm Information
customer pc not able to connect to network and not getting proper ip address range
Handling Process
found the illegal DHCP server and check the router . as per customer DHCP Server cannot be disabled on the LAN side .
Root Cause
after analysis , we found that some customer connect wan cable on the LAN Interafce of Router instead of WAN interface .

on the LAN interface of router , normally DHCP Server is enabled .

so , pc enabled with DHCP are getting ip address from this DHCP server instaed of original DHCP server .
1) DHCP snooping was enabled in global mode

2) DHCP snooping was enabled in the vlan

3) DHCP snooping trusted command  is required on the interface where legal DHCP server was connected

cmds are below

1) dhcp snooping enable
2) huawei # vlan
       huawei#dhcp snooping enable
3) interface gigabitethernet 0/0/1
     dhcp snooping enable
     dhcp snooping trusted