Filtering; Configuring Ip Source Guard Work Flow - Cisco SF500-24 Administration Manual

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- The interface is DHCP untrusted. All packets on trusted ports are
forwarded.
• If a port is DHCP trusted, filtering of static IP addresses can be configured,
even though IP Source Guard is not active in that condition by enabling IP
Source Guard on the port.
• When the ports status changes from DHCP untrusted to DHCP trusted, the
static IP address filtering entries remain in the Binding database, but they
become inactive.
• Port security cannot be enabled if source IP and MAC address filtering is
configured on a port.
• IP Source Guard uses TCAM resources and requires a single TCAM rule per
IP Source Guard address entry. If the number of IP Source Guard entries
exceeds the number of available TCAM rules, the extra addresses are
inactive.

Filtering

If IP Source Guard is enabled on a port then:
• DHCP packets allowed by DHCP Snooping are permitted.
• If source IP address filtering is enabled:
- IPv4 traffic: Only traffic with a source IP address that is associated with
the port is permitted.
- Non IPv4 traffic: Permitted (Including ARP packets).

Configuring IP Source Guard Work Flow

To configure IP Source Guard:
Enable DHCP Snooping in the IP Configuration > DHCP > Properties page or in the
Security > DHCP Snooping > Properties page.
Define the VLANs on which DHCP Snooping is enabled in the IP Configuration >
DHCP > Interface Settings page.
Configure interfaces as trusted or untrusted in the IP Configuration > DHCP >
DHCP Snooping Interface page.
Enable IP Source Guard in the Security > IP Source Guard > Properties page.
Cisco 500 Series Stackable Managed Switch Administration Guide Release 1.3
Security
IP Source Guard