ZyXEL ES-3124PWR User Guide - Page 193

IP Source Guard

Page 193 highlights

CHAPTER 24 IP Source Guard Use IP source guard to filter unauthorized DHCP and ARP packets in your network. 24.1 IP Source Guard Overview IP source guard uses a binding table to distinguish between authorized and unauthorized DHCP and ARP packets in your network. A binding contains these key attributes: • MAC address • VLAN ID • IP address • Port number When the Switch receives a DHCP or ARP packet, it looks up the appropriate MAC address, VLAN ID, IP address, and port number in the binding table. If there is a binding, the Switch forwards the packet. If there is not a binding, the Switch discards the packet. The Switch builds the binding table by snooping DHCP packets (dynamic bindings) and from information provided manually by administrators (static bindings). IP source guard consists of the following features: • Static bindings. Use this to create static bindings in the binding table. • DHCP snooping. Use this to filter unauthorized DHCP packets on the network and to build the binding table dynamically. • ARP inspection. Use this to filter unauthorized ARP packets on the network. If you want to use dynamic bindings to filter unauthorized ARP packets (typical implementation), you have to enable DHCP snooping before you enable ARP inspection. 24.1.1 DHCP Snooping Overview Use DHCP snooping to filter unauthorized DHCP packets on the network and to build the binding table dynamically. This can prevent clients from getting IP addresses from unauthorized DHCP servers. 24.1.1.1 Trusted vs. Untrusted Ports Every port is either a trusted port or an untrusted port for DHCP snooping. This setting is independent of the trusted/untrusted setting for ARP inspection. You can also specify the maximum number for DHCP packets that each port (trusted or untrusted) can receive each second. ES-3124 Series User's Guide 193

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ES-3124 Series User’s Guide
193
C
HAPTER
24
IP Source Guard
Use IP source guard to filter unauthorized DHCP and ARP packets in your network.
24.1
IP Source Guard Overview
IP source guard uses a binding table to distinguish between authorized and unauthorized
DHCP and ARP packets in your network. A binding contains these key attributes:
MAC address
VLAN ID
IP address
Port number
When the Switch receives a DHCP or ARP packet, it looks up the appropriate MAC address,
VLAN ID, IP address, and port number in the binding table. If there is a binding, the Switch
forwards the packet. If there is not a binding, the Switch discards the packet.
The Switch builds the binding table by snooping DHCP packets (dynamic bindings) and from
information provided manually by administrators (static bindings).
IP source guard consists of the following features:
Static bindings. Use this to create static bindings in the binding table.
DHCP snooping. Use this to filter unauthorized DHCP packets on the network and to
build the binding table dynamically.
ARP inspection. Use this to filter unauthorized ARP packets on the network.
If you want to use dynamic bindings to filter unauthorized ARP packets (typical
implementation), you have to enable DHCP snooping before you enable ARP inspection.
24.1.1
DHCP Snooping Overview
Use DHCP snooping to filter unauthorized DHCP packets on the network and to build the
binding table dynamically. This can prevent clients from getting IP addresses from
unauthorized DHCP servers.
24.1.1.1
Trusted vs. Untrusted Ports
Every port is either a trusted port or an untrusted port for DHCP snooping. This setting is
independent of the trusted/untrusted setting for ARP inspection. You can also specify the
maximum number for DHCP packets that each port (trusted or untrusted) can receive each
second.