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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 33 Configuring DHCP Snooping and IP Source Guard
Enabling IP Source Guard on a Port
•
IP source guard cannot coexist with PACLs.
•
IP source guard is not supported on EtherChannel-enabled ports, and EtherChannel is not supported
on IP source guard-enabled ports.
•
VLAN-based ACL features, such as static ARP inspection, are disabled when you enable IP source
guard.
•
We recommend that you enable high availability when using dynamic ARP inspection (DAI), DHCP
snooping, and IP source guard. If high availability is not enabled, clients have to renew their IP
addresses for these features to work after a switchover. For configuration details on DAI, see the
“Dynamic ARP Inspection” section on page 15-39
.
Enabling IP Source Guard on a Port
To enable IP source guard, perform this task in privileged mode:
Note
Before you can enable IP source guard, you must enable DHCP snooping on the VLAN to which the port
belongs. You must configure the port as either port based or in merge mode for security ACLs. You
should only enable IP source guard on DHCP-snooping untrusted ports.
This example shows how to enable IP source guard:
Console> (enable)
set port security-acl 3/1 port-based
Warning:Vlan-based ACL features will be disabled on ports 3/1.
ACL interface is set to port-based mode for port(s) 3/1.
Console> (enable)
set port dhcp-snooping 3/1 source-guard enable
IP Source Guard enabled on port(s) 3/1.
Console> (enable)
set port dhcp-snooping 1/2 trust enable
Port(s) 1/2 state set to trusted for DHCP Snooping.
Console> (enable)
set security acl ip dhcpsnoop permit dhcp-snooping
Successfully configured DHCP Snooping for ACL dhcpsnoop. Use 'commit' command to
save changes.
Console> (enable)
set security acl ip dhcpsnoop permit ip any any
dhcpsnoop editbuffer modified. Use 'commit' command to apply changes.
Console> (enable)
commit security acl dhcpsnoop
ACL commit in progress.
ACL 'dhcpsnoop' successfully committed.
Console> (enable)
set security acl map dhcpsnoop 10
Mapping in progress.
Task
Command
Step 1
Configure the port as port based.
set port security-acl 3/1 port-based
Step 2
Enable IP source guard.
set port dhcp-snooping 3/1 source-guard enable
Step 3
Enable DHCP snooping.
set security acl ip dhcpsnoop permit dhcp-snooping
Step 4
Allow the port to forward other traffic.
set security acl ip dhcpsnoop permit ip any any
Step 5
Save the ACL configuration.
commit security acl dhcpsnoop
Step 6
Enable the ACL on the VLAN.
set security acl map dhcpsnoop 10
Step 7
Enable DHCP-snooping trust on a port.
set port dhcp-snooping 1/2 trust enable