LevelOne FGL-2870 - Manual (Page 204)

Configuring the Switch
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IP Source Guard
IP Source Guard is a security feature that filters IP traffic on network interfaces
based on manually configured entries in the IP Source Guard table, or dynamic
entries in the DHCP Snooping table when enabled (see "DHCP Snooping" on page
3-143). IP source guard can be used to prevent traffic attacks caused when a host
tries to use the IP address of a neighbor to access the network. This section
describes commands used to configure IP Source Guard.
Configuring Ports for IP Source Guard
Use the IP Source Guard Port Configuration page to set the filtering type based on
source IP address or source IP address and MAC address pairs.
IP Source Guard is used to filter traffic on an insecure port which receives messages
from outside the network or fire wall, and therefore may be subject to traffic attacks
caused by a host trying to use the IP address of a neighbor.
Command Usage
• Setting source guard mode to SIP (Source IP) or SIP-MAC (Source IP and MAC)
enables this function on the selected port. Use the SIP option to check the VLAN
ID, source IP address, and port number against all entries in the binding table. Use
the SIP-MAC option to check these same parameters, plus the source MAC
address. If no matching entry is found, the packet is dropped.
• When enabled, traffic is filtered based upon dynamic entries learned via DHCP
snooping (see "DHCP Snooping Configuration" on page 3-144), or static
addresses configured in the source guard binding table.
• If IP source guard is enabled, an inbound packet’s IP address (SIP option) or both
its IP address and corresponding MAC address (SIP-MAC option) will be checked
against the binding table. If no matching entry is found, the packet will be dropped.
• Filtering rules are implemented as follows:
- If DHCP snooping is disabled (see page 3-144), IP source guard will check the
VLAN ID, source IP address, port number, and source MAC address (for the
SIP-MAC option). If a matching entry is found in the binding table and the entry
type is static IP source guard binding, the packet will be forwarded.
- If DHCP snooping is enabled, IP source guard will check the VLAN ID, source
IP address, port number, and source MAC address (for the SIP-MAC option). If
a matching entry is found in the binding table and the entry type is static IP
source guard binding, or dynamic DHCP snooping binding, the packet will be
forwarded.
- If IP source guard if enabled on an interface for which IP source bindings have
not yet been configured (neither by static configuration in the IP source guard
binding table nor dynamically learned from DHCP snooping), the switch will drop
all IP traffic on that port, except for DHCP packets.