Troubleshooting Tip: Automatically added entry in IP/MAC binding table

[mle2802]

Description	This article describes how to troubleshoot an issue where entries are automatically added in an IP/MAC binding table.
Scope	Fortigate
Solution	Checking the IP/MAC table config, only one entry is configured FGT_1 # config firewall ipmacbinding table FGT_1 (table) # show config firewall ipmacbinding table     edit 1         set ip 192.168.6.10         set mac 00:0c:29:ba:6f:c6         set status enable     next end However, there are extra entries when listing the firewall IP/MAC address pairs: FGT_1 # diagnose firewall ipmac list List firewall IP/MAC address pairs: ip=192.168.6.2 mac=00:0c:29:db:0a:bc act=01 flag=00 ip=192.168.6.10 mac=00:0c:29:ba:6f:c6 act=01 flag=00 This is the behavior when the command 'set ipmac enable' is configured on the interface which has DHCP server enabled. All DHCP leases will be added in the IP/MAC database automatically. To avoid this behavior, 'IP Address Assignment Rules' can be used to block the DHCP request and assign an IP only for the trusted host.  'IP Address Assignment Rules' can be found under System -> Interfaces: double-click on the interface to edit and expand the advanced option under DHCP settings. Verify the DHCP lease and the IP/MAC table again: