Configuring DHCP Relay Agent
615
n
■
You can configure up to eight external DHCP IP addresses in a DHCP server
group.
■
You can map multiple VLAN interfaces to one DHCP server group. But one
VLAN interface can be mapped to only one DHCP server group. If you execute
the
dhcp-server
groupNo command repeatedly, the new configuration
overwrites the previous one.
■
You need to configure the group number specified in the
dhcp-server
groupNo command in VLAN interface view by using the command
dhcp-server
groupNo
ip
ipaddress-address&<1-8> in advance.
Configuring a DHCP
Relay Agent to
Broadcast Responses to
Clients
Generally, the DHCP relay agent determines to broadcast or unicast responses
(including DHCP-OFFER, DHCP-ACK, or DHCP-NAK) from the DHCP server to the
clients according to the flag field in the DHCP-DISCOVER packet.
■
When the first bit of the flag field is set to 1, the DHCP relay agent broadcasts
the response packets to the clients.
■
When the flag field is set to 0, the DHCP relay agent unicasts the response
packets to the clients.
In actual networking, if clients have special requirements, Switch 7750 Ethernet
switches support the following commands so as to force the DHCP relay agent to
broadcast the responses to the clients. After this function is enabled, even if the
flag field in the DHCP-DISCOVER packet is set to 0, the DHCP relay agent still
broadcasts responses to the clients.
Specifying Gateways for
DHCP Clients
To implement this feature on the DHCP relay agent, you need to bind ports in a
VLAN to either the VLAN interface’s primary IP address or one of its secondary IP
addresses (a gateway address). The binding entries will be stored in a binding
table.
Upon receiving a DHCP request message with the giaddr field being 0 from a port
in this VLAN, the DHCP relay agent will search the binding table and then insert
the bound gateway IP address into the giaddr field of the message. If the DHCP
relay agent cannot find a match in the binding table, it inserts the primary IP
Map an interface to a DHCP
server group
interface
interface-type
interface-number
Required
By default, a VLAN interface is
not mapped to any DHCP
server group
dhcp-server
groupNo
Table 483
Configure an interface to operate in DHCP relay agent mode
Operation Command Description
Table 484
Configure the DHCP relay agent to broadcast responses to clients
Operation Command Description
Enter system view
system-view
-
Configure the DHCP
relay agent to
broadcast responses
to clients
dhcp relay reply
broadcast
Required
Generally, the DHCP relay agent determines
to broadcast or unicast responses to the
clients according to the flag field in the
DHCP-DISCOVER packet.
Summary of Contents for Switch 7754
Page 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Page 126: ...126 CHAPTER 14 SUPER VLAN ...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Page 718: ...718 CHAPTER 63 CLUSTER ...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...