Users Guide

Table Of Contents
In this scenario, in the VLT pairs (VLT Peer 1 and VLT Peer 2) VRRP is enabled and the virtual IP is configured to achieve
gateway redundancy.
Alternatively, you can configure VLAN anycast gateway to achieve the gateway redundancy. VRRP and anycast gateway are
mutually exclusive. The DHCP clients (Host 1, 2, 3) in VLAN 10 or VRF BLUE and DHCP clients (Host 1, 2, 3) in VLAN 20 or VRF
RED use VRRP virtual IP as the default gateway.
The DHCP relay helper-address is configured in VLAN 10 and VLAN 20 with the VRF name Services (DHCP Server reachable
VRF). For this use case, when server-override is enabled the VRRP virtual IP is used as server-override option when BOOTP
Relay request is sent to the DHCP server. The DHCP server sets the server-override option in the server identifier option in the
DHCP OFFER packet. The DHCP client uses the VRRP virtual IP or server-override option as destination IP in the DHCP unicast
packet. The DHCP relay forwards the packet to the DHCP server for further processing.
DHCP snooping
DHCP snooping is a layer 2 security feature that helps networking devices to monitor DHCP messages and block untrusted or
rogue DHCP servers.
When you enable DHCP snooping on a switch, it begins monitoring transactions between trusted DHCP servers and DHCP
clients and uses the information to build the DHCP snooping binding table. You configure interfaces that connect to DHCP
servers as trusted interfaces. All other interfaces are untrusted by default.
The DHCP snooping binding table contains the following information:
Client IP addresses
Client MAC addresses
Interface facing the clients
Client VLAN
System management
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