HP 5500 Ei 5500 Si Switch Series Configuration Guide
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• Assign a primary IP address and a secondary IP address to VLAN-interface 1 on the switch.
• Set the primary IP address of VLAN-interface 1 as the gateway address of the hosts on subnet
172.16.1.0/24, and the secondary IP address of VLAN-interface 1 as the gateway address of the
hosts on subnet 172.16.2.0/24.
Figure 14 Network diagram
Configuration procedure
# Assign a primary IP address and a secondary IP address to VLAN-interface 1.
system-view
[Switch] interface vlan-interface...](http://img.usermanuals.tech/thumb/36/58909/w64_hp-5500-ei-5500-si-switch-series-configuration-guide-506.png "Page 507
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• Assign a primary IP address and a secondary IP address to VLAN-interface 1 on the switch.
• Set the primary IP address of VLAN-interface 1 as the gateway address of the hosts on subnet
172.16.1.0/24, and the secondary IP address of VLAN-interface 1 as the gateway address of the
hosts on subnet 172.16.2.0/24.
Figure 14 Network diagram
Configuration procedure
# Assign a primary IP address and a secondary IP address to VLAN-interface 1.
system-view
[Switch] interface vlan-interface...")
29 Dynamic IP address allocation process Figure 16 Dynamic IP address allocation process 1. The client broadcasts a DHCP-DISCOVER message to locate a DHCP server. 2. A DHCP server offers configuration parameters such as an IP address to the client, in a DHCP-OFFER message. The sending mode of the DHCP-OFFER is determined by the flag field in the DHCP-DISCOVER message. For related information, see DHCP message format. 3. If several DHCP servers send offers to the client, the client accepts the first received offer, and broadcasts it in a DHCP-R EQUEST message to formally request the IP address. 4. All DHCP servers receive the DHCP-REQUEST message, but only the server from which the client accepts the offered IP address returns either a DHCP -ACK message to the client, confirming that the IP address has been allocated to the client, or a DHCP-NAK message, denying the IP address allocation. After the client receives the DHCP-ACK message, it broadcasts a gratuitous ARP packet to verify whether the IP address assigned by the server is already in use. If the client receives no response within the specified time, the client uses the assigned IP address. Otherwise, the client sends a DHCP-DECLINE message to the server to request an IP address again. IP addresses offered by other DHCP servers are still assignable to other clients. IP address lease extension The IP address dynamically allocated by a DHCP server to a client has a lease. When the lease expires, the IP address is reclaimed by the DHCP server. To continue using the IP address, the client must extend the lease duration. After half the lease duration, the DHCP client sends a DHCP-REQUEST unicast to the DHCP server to extend the lease. Depending on availability of the IP address, the DHCP server returns either a DHCP-ACK unicast confirming that the client’s lease has been extended, or a DHCP-NAK unicast denying the request. If the client receives no reply, it broadcasts an other DHCP-REQUEST message for lease extension after 7/8 lease duration. Again, depending on availability of the IP address, the DHCP server returns either a DHCP-ACK unicast confirming that the client’s lease has been extended, or a DHCP-NAK unicast denying the request.
30 DHCP message format Figure 17 shows the DHCP message format, which is ba sed on the BOOTP message format although DHCP uses some of the fields in significantly different ways. The numbers in parentheses indicate the size of each field in bytes. Figure 17 DHCP message format • op—Message type defined in option field. 1 = REQUEST, 2 = REPLY • htype , hlen —Hardware address type and length of a DHCP client. • hops —Number of relay agents a request message traveled. • xid—Transaction ID, a random number chosen by the client to identify an IP address allocation. • secs—Filled in by the client, the number of seconds elapsed since the client began address acquisition or renewal process. Currently this field is reserved and set to 0. • flags —The leftmost bit is defined as the BROADCAST (B) flag. If this flag is set to 0, the DHCP server sent a reply back by unicast; if this flag is set to 1, the DHCP server sent a reply back by broadcast. The remaining bits of the flags field are reserved for future use. • ciaddr—Client IP address if the client has an IP address that is valid and usable; otherwise, set to zero. • yiaddr—Your (client) IP address, assigned by the server. • siaddr—Server IP address, from which the client obtained configuration parameters. • giaddr—(Gateway) IP address of the first relay agent a request message traveled. • chaddr—Client hardware address. • sname —Server host name, from which the client obtained configuration parameters. • file—Bootfile name and path information, defined by the server to the client. • options —Optional parameters field that is variable in length, which includes the message type, lease duration, subnet mask, domain name server IP address, WINS IP address, and other information.
31 DHCP options D H C P us e s t h e s a m e m e s s a g e fo rm a t a s BO OT P, b u t D H C P us e s t h e O p t io n fi e l d t o c a rr y i n fo rm a t io n fo r dynamic address allocation and to provide additional configuration information to clients. Figure 18 DHCP option format Common DHCP options The following are common DHCP options: • Option 3 —Router option. It specifies the gateway address. • Option 6 —DNS server option. It specifies the DNS server’s IP address. • Option 33 —Static route option. It specifies a list of classful static routes (the destination addresses in these static routes are classful) that a client should add into its routing table. If both Option 33 and Option 121 exist, Option 33 is ignored. • Option 51 —IP address lease option. • Option 53 —DHCP message type option. It identifies the type of the DHCP message. • Option 55 —Parameter request list option. It is used by a DHCP client to request specified configuration parameters. The option contains values that correspond to the parameters requested by the client. • Option 60 —Vendor class identifier option. It is used by a DHCP client to identify its vendor, and by a DHCP server to distinguish DHCP clients by vendor class and assign specific IP addresses for the DHCP clients. • Option 66 —TFTP server name option. It specifies a TFTP server to be assigned to the client. • Option 67 —Bootfile name option. It specifies the bootfile name to be assigned to the client. • Option 121 —Classless route option. It specifies a list of classless static routes (the destination addresses in these static routes are classless) that th e requesting client should add to its routing table. If both Option 33 and Option 121 exist, Option 33 is ignored. • Option 15 0 —TFTP server IP address option. It specifies the TFTP server IP address to be assigned to the client. For more information about DHCP options, see RFC 2132 and RFC 3442. Custom options So m e o p t io n s, s u ch a s O p t io n 43 , O p t io n 82, a n d O p t io n 184, h ave n o u n i fie d d e fi n i t io n s i n R F C 2132. Vendor-specific option (Option 43) DHCP servers and clients use Option 43 to exchange vendor-specific configuration information. The DHCP client can obtain the following information through Option 43: • Auto-Configuration Server (ACS) parameters, including the ACS URL, username, and password.
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• Service provider identifier, which is acquired by the Customer Premises Equipment (CPE) from the
DHCP server and sent to the ACS for selecting vender-specific configurations and parameters.
• Preboot Execution Environment (PXE) server address, which is used to obtain the bootfile or other
control information from the PXE server.
1. Format of Option 43
Network configuration parameters are carried in different sub-options of Option 43 as shown
in Figure 19 .
Figure 19 Optio
n 43 format
{
Sub-option type —Type of a sub-option. The field value can be 0x01 (an ACS parameter
sub-option), 0x02 (a service provider identifier sub-option), or 0x80 (a PXE server address
sub-option).
{ Sub -option length —Length of a sub-option excluding the su b-option type and sub-option length
fields.
{ Sub-option value —Value of a sub-option. The value format varies with sub-options.
2. Format of the sub-option value field of Option 43
{ As shown in Figure 20 , the value field of the ACS parameter sub-option contains variable ACS
URL, ACS username, and ACS passwo rd separated by spaces (0x20):
Figure 20 ACS parameter sub-option value field
{
The value field of the service provider identifier sub-option contains the service provider
identifier.
{ Figure 21 shows the format of the value field of the PXE server address sub-option. The value of
the PXE server type can only be 0. The server number field indicates the number of PXE servers
contained in the sub-option. The server IP addre sses field contains the IP addresses of the PXE
servers.
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Figure 21 PXE server address sub-option value field
Relay agent option (Option 82)
Option 82 is the relay agent option in the option field of the DHCP message. It records the location
information of the DHCP client. When a DHCP relay agent or DHCP snooping device receives a client’s
request, it adds Option 82 to the request message and sends it to the server.
The administrator can locate the DHCP client to fu rther implement security control and accounting. The
Option 82 supporting server can also use such information to define individual assignment policies of IP
address and other parameters for the clients.
Option 82 involves at most 255 sub-options. At le ast one sub-option must be defined. The DHCP relay
agent supports three sub-options: su b-option 1 (Circuit ID). sub-option 2 (Remote ID) and sub-option 9
(private padding format).
Option 82 has no unified definition. Its padding formats vary with vendors.
There are two methods for configuring Option 82:
• User-defined method —Manually specify the content of Option 82.
• Non-user-defined method —Pad Option 82 in the default normal format, verbose format, private
format, or standard format.
If you choose normal format and verbose format, you can specify the code type for the sub-options as
ASCII or HEX.
• Normal padding format
{ Sub-option 1 —Contains the VLAN ID and interface number of the interface that received the
client’s request. The value of the sub-option type is 1, and that of the circuit ID type is 0.
Figure 22 Sub-option 1 in normal padding format
{
Sub-option 2 —Contains the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that rece ived the client’s request. The value of the
sub-option type is 2, and that of the remote ID type is 0.
Figure 23 Sub-option 2 in normal padding format
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• Verbose padding format
{ Sub-option 1 —Contains the user-specified access node identifier (ID of the device that adds
Option 82 in DHCP messages), and the type, number, and VLAN ID of the interface that
received the client’s request. The VLAN ID field has a fixed length of 2 bytes. All the other
padding contents of sub-option 1 are length variable. See Figure 24.
Figure 24 Sub-option 1 in verbose pa
dding format
{
Sub-option 2 —Contains the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that received the client’s request. It has the same format
as that in normal padding format. See Figure 23.
• Pr
ivate padding format
{ Sub-option 1 —Contains the VLAN ID of the interface that received the client’s request, module
(subcard number of the receiving port) and port (port number of the receiving port). The value
of the sub-option type is 1.
Figure 25 Sub-option 1 in private padding format
{
Sub-option 2 —Contains the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that rece ived the client’s request. The value of the
sub-option type is 2.
Figure 26 Sub-option 2 in private padding format
{
Sub-option 9 —Contains the sysname and the primary IP address of the Loopback0 interface.
The value of the sub-option type is 9.
Figure 27 Sub-option 9 in private padding format
• Standard padding format
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{ Sub-option 1 —Contains the VLAN ID of the interface that received the client’s request, module
(subcard number of the receiving port) and port (port number of the receiving port). The value
of the sub-option type is 1, and the value of the circuit ID type is 0.
Figure 28 Sub-option 1 in standard padding format
{
Sub-option 2 —Contains the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that received the client’s request. It has the same format
as sub-option 2 in normal padding format. See Figure 23.
Option 184
Option 184 is a reserved option, and parameters in the option can be defined as needed. The device
supports Option 184 carrying voice related parameters, so a DHCP client with voice functions can get an
IP address along with specified voice parameters from the DHCP server.
Option 184 involves the following sub-options:
• Sub-option 1 —IP address of the primary network calling processor, which serves as the network
calling control source and provides program downloads.
• Sub-option 2 —IP address of the backup network calling processor. DHCP clients contact the
backup when the primary is unreachable.
• Sub-option 3 —Voice VL AN ID and the result whether or not DHCP clients take this ID as the voice
VLAN.
• Sub-option 4 —Failover route that specifies the destination IP address and the called number. A
Session Initiation Protocol (SIP) user uses this IP address and number to reach another SIP user when
both the primary and backup calling processors are unreachable.
You must define sub-option 1 to make other sub-options take effect.
Protocols and standards
• RFC 2131, Dynamic Host Configuration Protocol
• RFC 2132, DHCP Options and BOOTP Vendor Extensions
• RFC 1542, Clarifications and Extensions for the Bootstrap Protocol
• RFC 3046, DHCP Relay Agent Information Option
• R FC 3442, The Classless Static Route Option for Dynamic Host Configuration Protocol (DHCP)
version 4
36 Configuring DHCP server The term interface in the DHCP features refers to Layer 3 interfaces, including VLAN interfaces and route-mode (or Layer 3) Ethernet ports. You can set an Ethernet port to operate in route mode by using the port link-mode route command (see the Layer 2—LAN Switching Configuration Guide ). Only HP 5500 EI switches support Layer 3 Ethernet port configuration. Overview The DHCP server is well suited to networks where: • Manual configuration and centralized management are difficult to implement. • Many hosts need to acquire IP addresses dynamically. This may be because the number of hosts exceeds the number of assignable IP addresses, so it is impossible to assign a fixed IP address to each host. For example, an ISP has a limited number of host addresses. • A few hosts need fixed IP addresses. In addition to assigning IP addresses to DHCP client s on public networks, a multi-VPN-instance customer edge (MCE) serving as the DHCP server can also assign IP addresses to DHCP clients on private networks. Note that the IP address ranges of public and private networks or those of private networks on the DHCP server cannot overlap each other. For more information about MCE, see Layer 3—IP Routing Configuration Guide . DHCP address pool Address pool types DHCP address pools include commo n and extended address pools. • Common address pool —Supports both static binding and dynamic allocation. • Extended address pool —Supports only dynamic allocation. Common address pool structure The common address pool database is organized as a tree. The root of the tree is the address pool for natural networks, branches are address pools for subnets, and leaves are addresses statically bound to clients. For the same level address pools, a previously configured pool has a higher selection priority than a new one. At the very beginning, subnets inherit network par ameters and clients inherit subnet parameters. Therefore, common parameters, for example a DNS server address, should be configured at the highest (network or subnet) level of the tree. IP address lease durations are not inherited. The new configuration at the higher level (parent) of the tree will be: • Inherited if the lower level (child) has no such configuration. • Overridden if the lower level (child) has such configuration.
37 NOTE: The extended address pools on a DHCP server are independent of each other and no inheritance relationship exists among them. Principles for selecting an address pool The DHCP server observes the following principles to select an address pool when assigning an IP address to a client: 1. If there is an address pool where an IP address is statically bound to the MAC address or ID of the client, the DHCP server will select this address pool and assign the static ally bound IP address to the client. For the configuration of this address pool, see Configuring static address alloc ation. 2. If the receiving interface has an extended address pool referenced, the DHCP server will assign an IP address from this address pool. If no IP addr ess is available in the address pool, the DHCP server will fail to assign an address to the client . For the configuration of such an address pool, see Configuring dynamic address allocation for an extended address p ool. 3. Otherwise, the DHCP server will select the smallest common address pool that contains the IP address of the receiving interface (if the client and the server reside on the same subnet), or the smallest common address pool that contains the IP address specified in the giaddr field of the client’s request (if a DHCP relay agent is in-betw een). If no IP address is available in the address pool, the DHCP server will fail to assign an addr ess to the client because it cannot assign an IP address from the parent address pool to the client. For the configuration of such an address pool, see Configuring dynamic address allocation . F or example, two common address pools, 1.1.1.0/24 and 1.1.1.0/25, are configured on the DHCP server. If the IP address of the interface receiving DHCP requests is 1.1.1.1/25, the DHCP server will select IP addresses for clients from address pool 1.1.1.0/25. If no IP address is available in the address pool, the DHCP server will fail to assign addresses to clients. If the IP address of the interface receiving DHCP requests is 1.1.1.130/25, the DHCP server will select IP addresses for clients from the 1.1.1.0/24 address pool. NOTE: To avoid wrong IP address allocation, keep the IP addresses for dynamic allocation within the subnet where the interface of the DHCP server or DHCP relay agent resides. IP address allocation sequence A DHCP server assigns an IP address to a client according to the following sequence: 1. The IP address statically bound to the client’s MAC address or ID. 2. The IP address that was ever assigned to the client. 3. The IP address designated by the Option 50 fiel d in a DHCP-DISCOVER message. Option 50 is the requested IP address field in DHCP-DISCOVER me ssages. It is padded by the client to specify the IP address that the client wants to obtain. The contents to be padded depend on the client. 4. The first assignable IP address found in an extended or common address pool. 5. The IP address that was a conflict or passed its lease duration. If no IP address is assignable, the server will not respond.
38 DHCP server configuration task list Task Remarks Configuring an address pool for the DHCP server Required. Enabling DHCP Required. Enabling the DHCP server on an interface Required. Applying an extended address pool on an interface Required by the extended address pool configuration. When configuring a common address pool, ignore this task. Configuring the DHCP server security functions Optional. Enabling client offline detection Optional. Enabling handling of Option 82 Optional. Specifying a server’s IP address for the DHCP client Optional. Specifying the threshold for sending trap messages Optional. Setting the DSCP value for DHCP packets Optional. Configuring an address pool for the DHCP server Configuration task list Task Remarks Creating a DHCP address pool Required. Configuring address allocation mode for a common address pool Configuring static address allocation Required to configure either of the two f or the common address pool configuration. Configuring dynamic address allocation Configuring dynamic address allocati on for an extended address pool Required for the extended address pool configuration. Configuring a domain name suffix for the client Optional. Configuring DNS servers for the client Configuring WINS servers and NetBIOS node type for the client Configuring BIMS server information for the client Configuring gateways for the client Configuring Option 184 parameters for the client with voice service Configuring the TFTP server and bootfile name for the client Specifying a server’s IP address for the DHCP client Configuring self-defined DHCP options