Installation manual

4-171
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check these same parameters, plus the source MAC address. Use the no 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 4-172) are automatically configured with
an infinite lease time. Dynamic entries learned via DHCP snooping are configured
by the DHCP server itself; static entries include a manually configured lease time.
• 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.
• Filtering rules are implemented as follows:
- If DHCP snooping is disabled (see page 4-163), 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 the 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
(dynamically learned via DHCP snooping or manually configured) are not yet
configured, the switch will drop all IP traffic on that port, except for DHCP
packets.
Example
This example enables IP source guard on port 5.
Related Commands
ip source-guard binding (4-172)
ip dhcp snooping (4-163)
ip dhcp snooping vlan (4-164)
Console(config)#interface ethernet 1/5
Console(config-if)#ip source-guard sip
Console(config-if)#