Configuring Dhcp Snooping; Command Usage - AMX NXA-ENET8-2POE Operation/Reference Manual

Configuring the NXA-ENET8-2POE

Configuring DHCP Snooping

Use the DHCP Snooping Configuration page to filter IP traffic on insecure ports for which the source address
cannot be identified via DHCP snooping.
FIG. 56 DHCP Snooping Configuration
DHCP Snooping Configuration parameters
• Snooping Mode
• Port
• Mode
The addresses assigned to DHCP clients on insecure ports can be carefully controlled using the dynamic
bindings registered with DHCP Snooping (or using the static bindings configured with IP Source Guard).
DHCP snooping allows a switch to protect a network from rogue DHCP servers or other devices which send
port-related information to a DHCP server. This information can be useful in tracking an IP address back to a
physical port.

Command Usage

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78
Enables DHCP snooping globally. When DHCP snooping is enabled, DHCP
request messages will be forwarded to trusted ports, and reply packets only
allowed from trusted ports. (Default: Disabled)
Port identifier
Enables or disables a port as a trusted source of DHCP messages. (Default:
Trusted)
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 a non-secure interface from
outside the network or fire wall. When DHCP snooping is enabled globally and enabled on a
VLAN interface, DHCP messages received on an untrusted interface from a device not listed in the
DHCP snooping table will be dropped.
Table entries are only learned for trusted interfaces. An entry is added or removed dynamically to
the DHCP snooping table when a client receives or releases an IP address from a DHCP server.
Each entry port identifier.
When DHCP snooping is enabled, DHCP messages entering an untrusted interface are filtered
based upon dynamic entries learned via DHCP snooping.
Filtering rules are implemented as follows:
If the global DHCP snooping is disabled, all DHCP packets are forwarded.
If DHCP snooping is enabled globally, 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.
If DHCP snooping is enabled globally, but the port is not trusted, it is processed as follows:
If the DHCP packet is a reply packet from a DHCP server (including OFFER, ACK or NAK
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messages), the packet is dropped.
If a DHCP DECLINE or RELEASE message is received from a client, the switch forwards the
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packet only if the corresponding entry is found in the binding table.
If a DHCP DISCOVER, REQUEST or INFORM message is received from a client, the packet is
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forwarded.
If the DHCP packet is not a recognizable type, it is dropped.
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NXA-ENET8-2POE Gigabit Ethernet Layer 2 PoE Switch