CLI Reference Guide-R04

Chapter 9 | General Security Measures
DHCPv6 Snooping
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◆ When the DHCPv6 Snooping Option 37 is enabled, clients can be identified by
the switch port to which they are connected rather than just their MAC address.
DHCPv6 client-server exchange messages are then forwarded directly between
the server and client without having to flood them to the entire VLAN.
◆ DHCPv6 snooping must be enabled for the DHCPv6 Option 37 information to
be inserted into packets. When enabled, the switch will either drop, keep or
remove option 37 information in incoming DHCPv6 packets. Packets are
processed as follows:
■
If an incoming packet is a DHCPv6 request packet with option 37
information, it will modify the option 37 information according to settings
specified with ipv6 dhcp snooping option remote-id policy command.
■
If an incoming packet is a DHCPv6 request packet without option 37
information, enabling the DHCPv6 snooping information option will add
option 37 information to the packet.
■
If an incoming packet is a DHCPv6 reply packet with option 37 information,
enabling the DHCPv6 snooping information option will remove option 37
information from the packet.
◆ When this switch inserts Option 37 information in DHCPv6 client request
packets, the switch’s MAC address (hexadecimal) is used for the remote ID.
Example
This example enables the DHCPv6 Snooping Remote-ID Option.
Console(config)#ipv6 dhcp snooping option remote-id
Console(config)#
ipv6 dhcp snooping
option remote-id
policy
This command sets the remote-id option policy for DHCPv6 client packets that
include Option 37 information. Use the no form to disable this function.
Syntax
ipv6 dhcp snooping option remote-id policy {drop | keep | replace}
no ipv6 dhcp snooping option remote-id policy
drop - Drops the client’s request packet instead of relaying it.
keep - Retains the Option 37 information in the client request, and
forwards the packets to trusted ports.
replace - Replaces the Option 37 remote-ID in the client’s request with the
relay agent’s remote-ID (when DHCPv6 snooping is enabled), and forwards
the packets to trusted ports.
Default Setting
drop