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Cisco Catalyst 3750-E User Manual

Cisco Catalyst 3750-E
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3-4
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 3 Assigning the Switch IP Address and Default Gateway
Assigning Switch Information
With DHCP-based autoconfiguration, no DHCP client-side configuration is needed on your switch.
However, you need to configure the DHCP server for various lease options associated with IP addresses.
If you are using DHCP to relay the configuration file location on the network, you might also need to
configure a Trivial File Transfer Protocol (TFTP) server and a Domain Name System (DNS) server.
Note We recommend a redundant connection between a switch stack and the DHCP, DNS, and TFTP servers.
This is to help ensure that these servers remain accessible in case one of the connected stack members
is removed from the switch stack.
The DHCP server for your switch can be on the same LAN or on a different LAN than the switch. If the
DHCP server is running on a different LAN, you should configure a DHCP relay device between your
switch and the DHCP server. A relay device forwards broadcast traffic between two directly connected
LANs. A router does not forward broadcast packets, but it forwards packets based on the destination IP
address in the received packet.
DHCP-based autoconfiguration replaces the BOOTP client functionality on your switch.
DHCP Client Request Process
When you boot up your switch, the DHCP client is invoked and requests configuration information from
a DHCP server when the configuration file is not present on the switch. If the configuration file is present
and the configuration includes the ip address dhcp interface configuration command on specific routed
interfaces, the DHCP client is invoked and requests the IP address information for those interfaces.
Figure 3-1 s
hows the sequence of messages that are exchanged between the DHCP client and the DHCP
server.
Figure 3-1 DHCP Client and Server Message Exchange
The client, Switch A, broadcasts a DHCPDISCOVER message to locate a DHCP server. The DHCP
server offers configuration parameters (such as an IP address, subnet mask, gateway IP address, DNS IP
address, a lease for the IP address, and so forth) to the client in a DHCPOFFER unicast message.
In a DHCPREQUEST broadcast message, the client returns a formal request for the offered
c
onfiguration information to the DHCP server. The formal request is broadcast so that all other DHCP
servers that received the DHCPDISCOVER broadcast message from the client can reclaim the IP
addresses that they offered to the client.
The DHCP server confirms that the IP address has been allocated to the client by returning a DHCPACK
uni
cast message to the client. With this message, the client and server are bound, and the client uses
configuration information received from the server. The amount of information the switch receives
depends on how you configure the DHCP server. For more information, see the “Configuring the TFTP
Server” section on page 3-7.
If the configuration parameters sent to the client in the DHCPOFFER unicast message are invalid (a
c
onfiguration error exists), the client returns a DHCPDECLINE broadcast message to the DHCP server.
Switch A
DHCPACK (unicast)
DHCPREQUEST (broadcast)
DHCPOFFER (unicast)
DHCPDISCOVER (broadcast)
DHCP server
51807

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Cisco Catalyst 3750-E Specifications

General IconGeneral
SeriesCatalyst 3750-E
Switching Capacity32 Gbps
Stacking Bandwidth32 Gbps
StackWise PlusYes
Layer SupportLayer 3
MAC Address Table Size12, 000 entries
RAM256 MB
Flash Memory64 MB
Memory256 MB DRAM, 64 MB Flash
Operating Temperature32 to 113°F (0 to 45°C)
Ports48 10/100/1000 Ethernet ports
Form FactorRack-mountable
Jumbo Frame SupportYes
Input Voltage100 to 240 VAC
Storage Temperature-25 to 70 °C
Relative Humidity10 to 90% non-condensing

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