Cisco Catalyst 2960-X User Manual

•
Intercepts all ARP requests and responses on untrusted ports
•
Verifies that each of these intercepted packets has a valid IP-to-MAC address binding before updating
the local ARP cache or before forwarding the packet to the appropriate destination
•
Drops invalid ARP packets
Dynamic ARP inspection determines the validity of an ARP packet based on valid IP-to-MAC address bindings
stored in a trusted database, the DHCP snooping binding database. This database is built by DHCP snooping
if DHCP snooping is enabled on the VLANs and on the switch. If the ARP packet is received on a trusted
interface, the switch forwards the packet without any checks. On untrusted interfaces, the switch forwards
the packet only if it is valid.
You enable dynamic ARP inspection on a per-VLAN basis by using the ip arp inspection vlan vlan-range
global configuration command.
In non-DHCP environments, dynamic ARP inspection can validate ARP packets against user-configured ARP
access control lists (ACLs) for hosts with statically configured IP addresses. You define an ARP ACL by
using the arp access-list acl-name global configuration command.
You can configure dynamic ARP inspection to drop ARP packets when the IP addresses in the packets are
invalid or when the MAC addresses in the body of the ARP packets do not match the addresses specified in
the Ethernet header. Use the ip arp inspection validate {[src-mac] [dst-mac] [ip]} global configuration
command.
Interface Trust States and Network Security
Dynamic ARP inspection associates a trust state with each interface on the switch. Packets arriving on trusted
interfaces bypass all dynamic ARP inspection validation checks, and those arriving on untrusted interfaces
undergo the dynamic ARP inspection validation process.
In a typical network configuration, you configure all switch ports connected to host ports as untrusted and
configure all switch ports connected to switches as trusted. With this configuration, all ARP packets entering
the network from a given switch bypass the security check. No other validation is needed at any other place
in the VLAN or in the network. You configure the trust setting by using theip arp inspection trust interface
configuration command.
Use the trust state configuration carefully. Configuring interfaces as untrusted when they should betrusted
can result in a loss of connectivity.
Caution
In the following figure, assume that both Switch A and Switch B are running dynamic ARP inspection on the
VLAN that includes Host 1 and Host 2. If Host 1 and Host 2 acquire their IP addresses from the DHCP server
connected to Switch A, only Switch A binds the IP-to-MAC address of Host 1. Therefore, if the interface
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
246 OL-29048-01
Configuring Dynamic ARP Inspection
Interface Trust States and Network Security

Cisco Catalyst 2960-X Specifications

General

Console port	RJ-45
USB 2.0 ports quantity	2
SFP module slots quantity	4
Installed SFP modules quantity	-
Gigabit Ethernet (copper) ports quantity	48
Basic switching RJ-45 Ethernet ports type	Gigabit Ethernet (10/100/1000)
Power source	AC
Input current	5 A
AC input voltage	100 - 240 V
Power consumption (typical)	60.9 W
Number of power supply units	1
Redundant power supply (RPS) support	Yes
Operating altitude	0 - 3000 m
Non-operating altitude	0 - 4000 m
Storage temperature (T-T)	-25 - 70 °C
Operating temperature (T-T)	-5 - 40 °C
Operating relative humidity (H-H)	10 - 95 %
Switching protocols	UDP, TCP, RADIUS/TACACS+
Number of VLANs	1023
Networking standards	IEEE 802.1ab, IEEE 802.1D, IEEE 802.1p, IEEE 802.1Q, IEEE 802.1s, IEEE 802.1w, IEEE 802.1x, IEEE 802.3, IEEE 802.3ab, IEEE 802.3ad, IEEE 802.3ae, IEEE 802.3af, IEEE 802.3ah, IEEE 802.3at, IEEE 802.3az, IEEE 802.3u, IEEE 802.3x, IEEE 802.3z
Throughput	107.1 Mpps
Jumbo frames	9216
Number of queues	8
MAC address table	16000 entries
Number of static routes	1000
DHCP features	DHCP server
Authentication	MAC-based authentication, Port-based authentication
Security algorithms	802.1x RADIUS, SNMP, SSH
Access Control List (ACL) rules	3
Switch type	Managed
Switch layer	L2/L3
Safety	UL 60950-1, CAN/CSA-C22.2 No. 60950-1, EN 60950-1, IEC 60950-1, AS/NZS 60950-1
Form factor	1U
Product color	Black
Total Power over Ethernet (PoE) budget	370 W
Power over Ethernet (PoE) ports quantity	24
Power over Ethernet plus (PoE+) ports quantity	12
Memory type	DRAM
Noise level	39 dB
Flash memory	128 MB
Internal memory	512 MB
Processor frequency	600 MHz
Mean time between failures (MTBF)	276870 h

Weight and Dimensions

Depth	368 mm
Width	445 mm
Height	45 mm
Weight	5800 g