Chapter 9
| General Security Measures
DHCPv6 Snooping
– 344 –
ipv6 dhcp snooping This command enables DHCPv6 snooping globally. Use the no form to restore the
default setting.
Syntax
[no] ipv6 dhcp snooping
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
â—† Network traffic may be disrupted when malicious DHCPv6 messages are
received from an outside source. DHCPv6 snooping is used to filter DHCPv6
messages received on an unsecure interface from outside the network or fire
wall. When DHCPv6 snooping is enabled globally by this command, and
enabled on a VLAN interface by the ipv6 dhcp snooping vlan command, DHCP
messages received on an untrusted interface (as specified by the no ipv6 dhcp
snooping trust command) from a device not listed in the DHCPv6 snooping
table will be dropped.
â—† When enabled, DHCPv6 messages entering an untrusted interface are filtered
based upon dynamic entries learned via DHCPv6 snooping.
â—† Table entries are only learned for trusted interfaces. Each entry includes a MAC
address, IPv6 address, lease time, binding type, VLAN identifier, and port
identifier.
â—† When DHCPv6 snooping is enabled, the rate limit for the number of DHCPv6
messages that can be processed by the switch is 100 packets per second. Any
DHCPv6 packets in excess of this limit are dropped.
â—† Filtering rules are implemented as follows:
â–
If global DHCPv6 snooping is disabled, all DHCPv6 packets are forwarded.
â–
If DHCPv6 snooping is enabled globally, and also enabled on the VLAN
where the DHCPv6 packet is received, DHCPv6 packets are forwarded for a
trusted port as described below.
â–
If DHCPv6 snooping is enabled globally, and also enabled on the VLAN
where the DHCP packet is received, but the port is not trusted, DHCP
packets are processed according to message type as follows:
DHCP Client Packet
â–
Request: Update entry in binding cache, recording client’s DHCPv6
Unique Identifier (DUID), server’s DUID, Identity Association (IA) type, IA
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