Configuring IP Source Guard

A.

IP Source Guard is a security feature that can be used to prevent IP spoofing attacks on a network. It works by checking the source IP address of incoming packets against a list of allowed IP addresses, and dropping any packets that do not match.

However, in order to use IP Source Guard successfully, certain other features must be configured on the network. Of the options given in the question, the correct answer is A. DHCP snooping.

DHCP snooping is a feature that can be used to prevent rogue DHCP servers on a network. It works by monitoring DHCP traffic on a switch, and building a database of valid DHCP servers based on the DHCP messages that are observed. When DHCP snooping is enabled, the switch will only allow DHCP traffic from these trusted servers, and will drop any DHCP traffic from untrusted sources.

The reason why DHCP snooping is required for IP Source Guard is that IP Source Guard relies on the switch being able to determine the source IP address of incoming packets. In most cases, the source IP address is assigned by a DHCP server, so if there are rogue DHCP servers on the network, they could potentially assign a spoofed IP address to a device, which would then be allowed by IP Source Guard.

By enabling DHCP snooping, the switch can ensure that only legitimate DHCP servers are allowed on the network, which in turn ensures that IP Source Guard can accurately determine the source IP address of incoming packets.

Option B, Dot1x, is a feature that can be used for network access control, but it is not directly related to IP Source Guard. Option C, Dynamic ARP Inspection, is a feature that can be used to prevent ARP spoofing attacks, but it is not required for IP Source Guard to function. Option D, port security, is a feature that can be used to restrict the number of MAC addresses that are allowed on a switch port, but it is also not directly related to IP Source Guard.