User manual

C HAPTER 4 | Configuring the Switch
Configuring Security
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CONFIGURING 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
"Configuring DHCP Snooping"). 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.
CONFIGURING GLOBAL AND PORT SETTINGS FOR IP SOURCE GUARD
Use the IP Source Guard Configuration page 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. IP Source Guard filters traffic type based on
the source IP address and MAC address pairs found in the DHCP Snooping
table, or based upon static entries configured in the IP Source Guard Table.
PATH
Advanced Configuration, Security, Network, IP Source Guard, Configuration
COMMAND USAGE
◆ When IP Source Guard is enabled globally and on a port, the switch
checks the VLAN ID, source IP address, and port number against all
entries in the DHCP Snooping binding table and IP Source Guard Static
Table. If no matching entry is found, the packet is dropped.
N OTE : Multicast addresses cannot be used by IP Source Guard.
◆ When enabled, traffic is filtered based upon dynamic entries learned via
DHCP snooping (see "Configuring DHCP Snooping"), or static addresses
configured in the source guard binding table.
◆ If IP source guard is enabled, an inbound packet’s IP address 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 107), IP source guard will
check the VLAN ID, source IP address, and port number. 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, and port number. 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.