DHCP Snooping

• DHCP snooping prevents the damage inflicted by several attacks that use DHCP.
• DHCP snooping causes a switch to examining DHCP messages & filter the inappropriate.
• DHCP snooping builds a table of IP address & port mappings
• this table builds based on the known DHCP messages
• this table is called the  DHCP snooping binding table.
• This DHCP snooping binding table can be used by DAI & IP source Guard feature.
• DHCP snooping defeats certain attacks (man in the middle attack using DHCP) by considering port as untrusted.
• All DHCP messages on trusted ports are only allowed by DHCP snooping.
• To this DHCP clients should exist on untrusted ports.
• As a result, the switch filters incoming DHCP messages that are only sent by servers.
• From design point of view unused & unsecured user ports would be configured as untrusted to DHCP snooping.
• DHCP snooping examine the DHCP client messages on untrusted ports because other attacks can be made using DHCP client messages.
• DHCP servers identify clients based on their client hardware address as listed in the DHCP request.
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