Netgear CSM4532 Software Administration Manual - Page 130

IP Source Guard Overview

Page 130 highlights

4.2.1.3. DHCP Snooping Logging and Rate Limits The DHCP snooping application processes incoming DHCP messages. For DHCPRELEASE and DHCPDECLINE messages, the application compares the receive interface and VLAN with the client interface and VLAN in the bindings database. If the interfaces do not match, the application logs the event and drops the message. For valid client messages, DHCP snooping compares the source MAC address to the DHCP client hardware address. When there is a mismatch, DHCP snooping drops the packet and generates a log message if logging of invalid packets is enabled. If DHCP relay co-exists with DHCP snooping, DHCP client messages are sent to DHCP relay for further processing. To prevent DHCP packets from being used as a DoS attack when DHCP snooping is enabled, the snooping application enforces a rate limit for DHCP packets received on interfaces. DHCP snooping monitors the receive rate on each interface separately. If the receive rate exceeds a configurable limit, DHCP snooping brings down the interface. Administrative intervention is necessary to enable the port, either by using the no shutdown command in Interface Config mode. 4.2.2. IP Source Guard Overview IPSG is a security feature that filters IP packets based on source ID. This feature helps protect the network from attacks that use IP address spoofing to compromise or overwhelm the network. The source ID may be either the source IP address or a {source IP address, source MAC address} pair. You can configure: • Whether enforcement includes the source MAC address • Static authorized source IDs The DHCP snooping bindings database and static IPSG entries identify authorized source IDs. IPSG can be enabled on physical and Port-channel ports. If you enable IPSG on a port where DHCP snooping is disabled or where DHCP snooping is enabled but the port is trusted, all IP traffic received on that port is dropped depending on the admin-configured IPSG entries. 4.2.2.1. IPSG and Port Security IPSG interacts with port security, also known as port MAC locking to enforce the source MAC address. Port security controls source MAC address learning in the layer 2 forwarding database (MAC address table). When a frame is received with a previously unlearned source MAC address, port security queries the IPSG feature to determine whether the MAC address belongs to a valid binding. If IPSG is disabled on the ingress port, IPSG replies that the MAC is valid. If IPSG is enabled on the ingress port, IPSG checks the bindings database. If the MAC address is in the bindings database and the binding matches the VLAN the frame was received on, IPSG replies that the MAC is valid. If the MAC is not in the bindings database, IPSG informs port security that the frame is a security violation. NETGEAR M4500 Series Switches Software Administration Manual 130

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NETGEAR M4500 Series Switches Software Administration Manual
130
4.2.1.3.
DHCP Snooping Logging and Rate Limits
The DHCP snooping application processes incoming DHCP messages. For DHCPRELEASE and DHCPDECLINE
messages, the application compares the receive interface and VLAN with the client interface and VLAN in the
bindings database. If the interfaces do not match, the application logs the event and drops the message. For
valid client messages, DHCP snooping compares the source MAC address to the DHCP client hardware
address. When there is a mismatch, DHCP snooping drops the packet and generates a log message if logging of
invalid packets is enabled.
If DHCP relay co-exists with DHCP snooping, DHCP client messages are sent to DHCP relay for further
processing.
To prevent DHCP packets from being used as a DoS attack when DHCP snooping is enabled, the snooping
application enforces a rate limit for DHCP packets received on interfaces. DHCP snooping monitors the receive
rate on each interface separately. If the receive rate exceeds a configurable limit, DHCP snooping brings down
the interface. Administrative intervention is necessary to enable the port, either by using the
no shutdown
command in Interface Config mode.
4.2.2.
IP Source Guard Overview
IPSG is a security feature that filters IP packets based on source ID. This feature helps protect the network from
attacks that use IP address spoofing to compromise or overwhelm the network.
The source ID may be either the source IP address or a {source IP address, source MAC address} pair. You can
configure:
Whether enforcement includes the source MAC address
Static authorized source IDs
The DHCP snooping bindings database and static IPSG entries identify authorized source IDs. IPSG can be
enabled on physical and Port-channel ports.
If you enable IPSG on a port where DHCP snooping is disabled or where DHCP snooping is enabled but the
port is trusted, all IP traffic received on that port is dropped depending on the admin-configured IPSG entries.
4.2.2.1.
IPSG and Port Security
IPSG interacts with port security, also known as port MAC locking to enforce the source MAC address. Port
security controls source MAC address learning in the layer 2 forwarding database (MAC address table). When
a frame is received with a previously unlearned source MAC address, port security queries the IPSG feature to
determine whether the MAC address belongs to a valid binding.
If IPSG is disabled on the ingress port, IPSG replies that the MAC is valid. If IPSG is enabled on the ingress port,
IPSG checks the bindings database. If the MAC address is in the bindings database and the binding matches
the VLAN the frame was received on, IPSG replies that the MAC is valid. If the MAC is not in the bindings
database, IPSG informs port security that the frame is a security violation.