Edge-Core ECS3510-28T Management Manual page 892

| General Security Measures
C 24
HAPTER
DHCPv4 Snooping
ip dhcp snooping
Table 91: DHCP Snooping Commands (Continued)
Command
ip dhcp snooping database
flash
show ip dhcp snooping
show ip dhcp snooping
binding
This command enables DHCP snooping globally. Use the no form to restore
the default setting.
S
YNTAX
[no] ip dhcp snooping
D S
EFAULT ETTING
Disabled
C M
OMMAND ODE
Global Configuration
C U
OMMAND SAGE
◆ Network traffic may be disrupted when malicious DHCP messages are
received from an outside source. DHCP snooping is used to filter DHCP
messages received on an unsecure interface from outside the network
or fire wall. When DHCP snooping is enabled globally by this command,
and enabled on a VLAN interface by the
command, DHCP messages received on an untrusted interface (as
specified by the no ip dhcp snooping trust
listed in the DHCP snooping table will be dropped.
When enabled, DHCP messages entering an untrusted interface are
◆
filtered based upon dynamic entries learned via DHCP snooping.
Table entries are only learned for trusted interfaces. Each entry
◆
includes a MAC address, IP address, lease time, VLAN identifier, and
port identifier.
◆ When DHCP snooping is enabled, the rate limit for the number of DHCP
messages that can be processed by the switch is 100 packets per
second. Any DHCP packets in excess of this limit are dropped.
Filtering rules are implemented as follows:
◆
If global DHCP snooping is disabled, all DHCP packets are
■
forwarded.
If DHCP snooping is enabled globally, and also enabled on the VLAN
■
where the DHCP packet is received, all DHCP packets are forwarded
for a trusted port. If the received packet is a DHCP ACK message, a
dynamic DHCP snooping entry is also added to the binding table.
– 892 –
Function
Writes all dynamically learned snooping entries to
flash memory
Shows the DHCP snooping configuration settings
Shows the DHCP snooping binding table entries
ip dhcp snooping vlan
command) from a device not
Mode
PE
PE
PE