Chapter 12
| Security Measures
IP Source Guard
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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 346). 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 Security > 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.
Note:
Multicast addresses cannot be used by IP Source Guard.
◆ When enabled, traffic is filtered based upon dynamic entries learned via DHCP
snooping (see “DHCP Snooping” on page 346), 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 348), 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.
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