Cisco Catalyst 2960-X User Manual

switch) is configured with a helper address to enable broadcast forwarding and to transfer DHCP messages
between the clients and the server.
Figure 13: DHCP Relay Agent in a Metropolitan Ethernet Network
When you enable the DHCP snooping information option 82 on the switch, the following sequence of
events occurs:
•
The host (DHCP client) generates a DHCP request and broadcasts it on the network.
•
When the switch receives the DHCP request, it adds the option-82 information in the packet. By default,
the remote-ID suboption is the switch MAC address, and the circuit-ID suboption is the port identifier,
vlan-mod-port, from which the packet is received.You can configure the remote ID and circuit ID.
•
If the IP address of the relay agent is configured, the switch adds this IP address in the DHCP packet.
•
The switch forwards the DHCP request that includes the option-82 field to the DHCP server.
•
The DHCP server receives the packet. If the server is option-82-capable, it can use the remote ID, the
circuit ID, or both to assign IP addresses and implement policies, such as restricting the number of IP
addresses that can be assigned to a single remote ID or circuit ID. Then the DHCP server echoes the
option-82 field in the DHCP reply.
•
The DHCP server unicasts the reply to the switch if the request was relayed to the server by the switch.
The switch verifies that it originally inserted the option-82 data by inspecting the remote ID and possibly
the circuit ID fields. The switch removes the option-82 field and forwards the packet to the switch port
that connects to the DHCP client that sent the DHCP request.
In the default suboption configuration, when the described sequence of events occurs, the values in these
fields do not change (see the illustration,Suboption Packet Formats):
•
Circuit-ID suboption fields
◦
Suboption type
◦
Length of the suboption type
◦
Circuit-ID type
◦
Length of the circuit-ID type
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
212 OL-29048-01
Configuring DHCP
Option-82 Data Insertion

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