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Implementing Cisco Networking Solutions by Harpreet Singh

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IP source guard

IP source guard is a technique available on layer 2 Ethernet switches to prevent IP spoofing. If the hosts on the LAN are supposed to get IP addresses through DHCP, we want only valid users who have a valid DHCP address to transmit on the network. The IP source guard feature helps achieve that functionality by snooping on the DHCP packets and creating a database within the switch on which IP addresses have been assigned by DHCP.

When this feature is initially configured, all IP traffic on the port is blocked except for the DHCP packets that are captured via DHCP snooping. When a client receives a valid IP address from the DHCP server, a port access control list (PACL) is automatically installed on the LAN port that permits ...

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