C
HAPTER
25
| General Security Measures
IP Source Guard
– 684 –
ip source-guard This command configures the switch to filter inbound traffic based source
IP address, or source IP address and corresponding MAC address. Use the
no form to disable this function.
SYNTAX
ip source-guard {sip | sip-mac}
no ip source-guard
sip - Filters traffic based on IP addresses stored in the binding
table.
sip-mac - Filters traffic based on IP addresses and corresponding
MAC addresses stored in the binding table.
DEFAULT SETTING
Disabled
COMMAND MODE
Interface Configuration (Ethernet)
COMMAND USAGE
◆ 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.
◆ Setting source guard mode to “sip” or “sip-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. Use the no ip source guard command to disable
this function on the selected port.
◆ When enabled, traffic is filtered based upon dynamic entries learned via
DHCP snooping, or static addresses configured in the source guard
binding table.
◆ Table entries include a MAC address, IP address, lease time, entry type
(Static-IP-SG-Binding, Dynamic-DHCP-Binding, VLAN identifier, and
port identifier.
◆ Static addresses entered in the source guard binding table with the ip
source-guard binding command (page 682) are automatically
configured with an infinite lease time. Dynamic entries learned via
DHCP snooping are configured by the DHCP server itself.
◆ If the 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.
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