Setup Guide

Table Of Contents
made. However, DHCPRELEASE and DHCPDECLINE packets are allowed so that the DHCP snooping table can decrease in size.
After the table usage falls below the maximum limit of 4000 entries, new IP address assignments are allowed.
NOTE: DHCP server packets are dropped on all non-trusted interfaces of a system configured for DHCP snooping. To
prevent these packets from being dropped, configure ip dhcp snooping trust on the server-connected port.
DHCP Snooping for a Multi-Tenant Host
You can configure the DHCP snooping feature such that multiple IP addresses are expected for the same MAC address. You
can use the ip dhcp snooping command multiple times to map the same MAC address with different IP addresses. This
configuration is also used for dynamic ARP inspection (DAI) and source address validation (SAV). The DAI and SAV tables
reflect the same entries in the DHCP snooping binding table.
NOTE: If you enable DHCP Option 82 using the ip dhcp relay command, by default, the remote-ID field contains the
MAC address of the relay agent. If you configure the remote ID as the host name in a VLT setup, configure different host
names on both VLT peers. If you configure the remote ID with your own string, ensure that your strings are different on
both VLT peers.
DHCP Snooping in a VLT Setup
In a VLT setup, the DHCP snooping binding table synchronizes between the VLT nodes. Similarly, the DAI and SAV tables also
synchronize between VLT nodes. For this feature to work in a VLT setup, make sure that DHCP relay, DHCP snooping, SAV, and
DAI configurations are identical between the VLT peer nodes.
Enabling DHCP Snooping
To enable DHCP snooping, use the following commands.
1. Enable DHCP snooping globally.
CONFIGURATION mode
ip dhcp snooping
2. Specify ports connected to DHCP servers as trusted.
INTERFACE mode
INTERFACE PORT EXTENDER mode
ip dhcp snooping trust
3. Enable DHCP snooping on a VLAN.
CONFIGURATION mode
ip dhcp snooping vlan name
Enabling IPv6 DHCP Snooping
To enable IPv6 DHCP snooping, use the following commands.
1. Enable IPv6 DHCP snooping globally.
CONFIGURATION mode
ipv6 dhcp snooping
2. Specify ports connected to IPv6 DHCP servers as trusted.
INTERFACE mode
ipv6 dhcp snooping trust
3. Enable IPv6 DHCP snooping on a VLAN or range of VLANs.
CONFIGURATION mode
ipv6 dhcp snooping vlan vlan-id
Dynamic Host Configuration Protocol (DHCP)
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