Network parameters such as IP addresses, subnet masks, gateways and DNSs are required for computers and mobile devices to access the network. There are two ways to configure IP addresses: static address assignment and dynamic address assignment.

Static address assignment requires manually inputting network parameters. Ordinary users’ lack of understanding on network parameters often leads to misconfiguration, so that the network cannot be accessed normally; and address conflicts caused by arbitrary IP address configuration are frequent. Wireless networks providing Internet access in public places such as hotels and restaurants, as well as 4G and 5G access for cell phones, are all temporary access, and the most convenient way is to automatically configure IP addresses and other parameters for the accessing device.

This chapter introduces the working principles of DHCP, and configures Huawei routers as DHCP servers to configure dynamic addresses for computers and mobile devices in the network.

11.1 Application Scenarios of Static Addresses and Dynamic Addresses

There are two ways to configure IP addresses for computers: the first is to manually specify configuration information such as IP addresses, subnet masks, gateways and DNS, and the IP addresses obtained in this way are called static addresses; the second is to use a DHCP server to specify configuration information IP addresses, subnet masks, gateways and DNSs for computers, and the addresses obtained in this way are called dynamic addresses.

  1. 1.

    The problems of manual configuration of network parameters

    1. (a)

      Many parameters are difficult to understand. For ordinary users, it is most desirable that they are able to access the Internet simply by connecting the network cable or connect to Wi-Fi without any other settings needed. If ordinary users are required to configure IP addresses, subnet masks, gateways, DNSs and other parameters in order to access the Internet, each time the network administrator also needs to provide an unused IP address.

    2. (b)

      High workload. If there are a large number of computers in the enterprise network, manual configuration by the network administrator is a massive workload and repetitive work, as the network administrator needs to plan the IP addresses in advance and assign them to individuals.

    3. (c)

      Low utilization rate. Each person in the enterprise network uses a fixed IP address, leading to low utilization rate of IP address.

      Some addresses may be in a long-term unused state. For example, if a Mr. Zhang goes on a business trip for a month, the IP address assigned to his computer will not be used for a long time. Meanwhile, new IP addresses need to be assigned to new employees.

    4. (d)

      Poor flexibility. Due to the emergence of WLAN, the terminal location is no longer fixed, so when the wireless terminal moves to an area covered by another wireless network, the IP address may need to be reconfigured.

  2. 2.

    Application scenario of static addresses

    1. (a)

      Computers do not often change their location in the network. For example, in school server rooms, the location of desktop computers is fixed, so static addresses are usually used. And to make it easier for student to access resources, IP addresses are also set according to certain rules, such as setting the IP address of the computer in the first row of the fourth column to 192.168.0.14, and the IP address of the computer in the third row of the second column to 192.168.0.32.

    2. (b)

      Enterprise servers also use fixed IP addresses (static addresses), which is to facilitate users to use IP addresses to access the server. For example, enterprise Web servers, FTP servers, domain controllers, file servers and DNS servers usually use static addresses.

  3. 3.

    Application scenario of dynamic addresses

    1. (a)

      Computers in the network are not fixed. For example, for the School of Software, each classroom belongs to a network segment: the network of Class 202 is network segment 10.7.202.0/24, the network of Class 204 is network segment 10.7.204.0/24. When students move from Class 202 to Class 204, the IP addresses of their laptops will have to be changed. If you ask the students to change the IP address (static address) by themselves, and the address configured may have already been used by other students’ laptops. Manually assigning addresses to mobile devices is troublesome, and moreover, the assigned addresses are prone to conflict with the others. If a DHCP server is used to uniformly assign addresses, no conflicts will arise.

    2. (b)

      For devices connected via Wi-Fi, usually, their addresses are also automatically assigned by a DHCP server. Accessing the network via Wi-Fi is supposed to be convenient, and it would be inconvenient if you have to set the IP address, subnet mask, gateway and DNS before you can access the Internet after connecting to Wi-Fi.

11.2 Working Principles of DHCP

11.2.1 Basic Concepts of DHCP

In order to solve the shortcomings of traditional static manual configuration method, Dynamic Host Configuration Protocol (DHCP) came into being. It can dynamically assign IP addresses to hosts. DHCP adopts C/S (Client/Server) architecture, and hosts only need to set the mode to obtain an IP address automatically from the server, so that the network can be directly used once it is connected to the network.

As shown in Fig. 11.1, the DHCP client can be a wireless mobile device, a laptop or a desktop computer. As long as the mode is set to obtain an IP address automatically (which is the default mode), the device becomes an DHCP client. The DHCP server can be a Windows server, Linux server, or Huawei Layer 3 device and router. DHCP client sends a DHCP request, and DHCP server receives the request and provides the client with an available address and parameters such as subnet mask, gateway and DNS.

Fig. 11.1
figure 1

DHCP working illustration

Full size image

DHCP has the following advantages.

  1. 1.

    Unified management. IP addresses are obtained from the address pool of DHCP server, and the server will record and maintain the usage status of IP addresses, such as which IP addresses have been used and which addresses have not been used, so as to uniformly assign and manage IP addresses.

  2. 2.

    Address lease period. DHCP introduces the concept of lease period. For the assigned IP address, if the terminal has not renewed the lease after the lease period expires, the server will conclude that the terminal no longer needs the IP address and will take the address back, and this IP address can be assigned to other terminals.

11.2.2 Working Process of DHCP

  1. 1.

    When a DHCP client needs to obtain a new IP address

    1. (a)

      It is the first time for the client computer to obtain an IP address from the DHCP server.

    2. (b)

      The IP address originally rented by the client computer has been taken back by the DHCP server and rented to other computers, so the client needs to rent a new IP address from the DHCP server.

    3. (c)

      The client releases the original IP address rented and requests a new one.

    4. (d)

      The client computer has changed its network interface card.

    5. (e)

      The client computer has moved to another network segment.

  2. 2.

    Types of DHCP packets

    In the above five cases, DHCP client and DHCP server will communicate with each other through the following four types of packets, and the working process of DHCP is shown in Fig. 11.2.

    1. (a)

      DHCP Discover.

      The DHCP client discovers available DHCP servers by broadcasting a DHCP Discover packet to the network.

      The computer that sets the IP address to automatic mode is the DHCP client. It has no idea who is the DHCP server in the network and has no address. DHCP client sends a broadcast packet to request the address, and all devices in the network can receive the request. The source IP address of the broadcast packet is 0.0.0.0 and the destination IP address is 255.255.255.255.

    2. (b)

      DHCP Offer.

      The DHCP server answers the client’s request by broadcasting a DHCP Offer packet to the network.

      When a DHCP server receives a DHCP Discover packet broadcasted by a DHCP client, all DHCP servers in the network will broadcast a DHCP Offer packet to the network. The so-called DHCP Offer packet is the information used by the DHCP server to provide IP address to the DHCP client.

    3. (c)

      DHCP Request.

      The DHCP client broadcasts a DHCP Request packet to the network to select IP addresses offered by multiple servers.

      After receiving a DHCP Offer packet from a server, the DHCP client broadcasts a DHCP Request packet to the network to accept the assignment. The DHCP Request packet contains the identification of the DHCP server that provides the lease for the client, so that other DHCP servers will revoke the assignment to this client after receiving this packet and the IP addresses that should have been assigned are withdrawn for responding to the lease request from other clients.

    4. (d)

      DHCP ACK (DHCP Acknowledgement)

      The selected DHCP server broadcasts a DHCP ACK packet to the network to confirm the client’s selection.

      After the DHCP server receives the DHCP Request packet broadcasted by the client, it then broadcasts a DHCP ACK packet to the network. The so-called DHCP ACK packet is the information sent by the DHCP server to the DHCP client to confirm the successful generation of the IP address lease. This information contains the valid lease of the IP address and other IP configuration information.

      After the DHCP client receives the DHCP ACK information, the process of obtaining an IP address is complete and this IP address can be used to communicate with other computers in the network.

      Think about it: why doesn’t the DHCP client directly use the IP address after receiving the DHCP Offer, but send a DHCP Request to inform the server?

      The broadcasted DHCP Request message informs other DHCP servers in the network that the client has selected an IP address assigned by a server, so as to ensure that other servers can retrieve the IP address assigned to the client through unicast DHCP Offer.

Fig. 11.2
figure 2

DHCP working process

Full size image

11.2.3 Lease Renewal

Before the lease expires, the DHCP client needs to renew the address lease assigned to it from the server.

  1. 1.

    Two methods of lease renewal.

    1. (a)

      Automatic renewal.

      DHCP automatically renew its lease. as soon as 50 percent of the lease duration has expired, A DHCP client automatically attempts to renew its lease, as shown in Fig. 11.3.

    2. (b)

      Manual renewal.

      If you need to update the DHCP configuration information immediately, you can manually renew an IP address lease. For example, if we want the DHCP client to immediately get the address of a newly installed router from the DHCP server, you simply need to renew the lease on the client side.

      You can directly execute the: ipconfig /renew command at the command prompt of the client.

  2. 2.

    The process of automatic renewal

    The DHCP client renews its lease periodically according to the set time to ensure that it is using the latest configuration information. When the lease expires and the client still has not renewed its address lease, the DHCP client will lose the address lease and start a DHCP lease generation process. The DHCP lease renewal process is as follows.

    1. (a)

      When 50% of the lease duration has expired, the client sends a request to the DHCP server, asking to renew and extend the current lease. The client sends a request directly to the DHCP server and can re-send it up to 3 times, at 4 s, 8 s and 16 s respectively.

    2. (b)

      If a server responds a DHCP Offer message to renew the client’s current lease, the client renews the lease with the information provided by the server and continues to work.

      If the client does not get a response from the original server half way through its lease duration, the client broadcasts a DHCP Request at 87.5% of the lease term, and any DHCP server can respond. This process is called rebinding.

    3. (c)

      If the lease is terminated and there is no connection to the server, the client must immediately stop using its leased IP address. The client then performs the same process as during its initial startup to obtain a new IP address lease.

Fig. 11.3
figure 3

DHCP lease renewal

Full size image

11.3 DHCP Service Configuration

As shown in Fig. 11.4, a company has three departments; the network of the sales department uses network segment 192.168.1.0/24, the network of the marketing department uses network segment 192.168.2.0/24, and the network of the R&D department uses network segment 172.16.5.0/24. Now you have to configure router AR1 as a DHCP server to assign IP addresses to the computers in these three departments.

Fig. 11.4
figure 4

DHCP network topology

Full size image

Create an address pool vlan1 for the sales department on AR1, vlan1 is the name of the address pool, and the name can be specified as you like.

[AR1]dhcp enable --Enable the global DHCP service [AR1]ip pool vlan1 --Create an address pool for VLAN 1 [AR1-ip-pool-vlan1]network 192.168.1.0 mask 24 --Specify the network segment of the address pool [AR1-ip-pool-vlan1]gateway-list 192.168.1.1 --Specify the gateway of the address pool [AR1-ip-pool-vlan1]dns-list 8.8.8.8 --Specify the DNS server [AR1-ip-pool-vlan1]dns-list 222.222.222.222 --Specify the second DNS server [AR1-ip-pool-vlan1]lease day 0 hour 8 minute 0 --Address lease, the time the client is allowed to use [AR1-ip-pool-vlan1]excluded-ip-address 192.168.1.1 192.168.1.10 --Specify the excluded address range Error:The gateway cannot be excluded. --Gateway cannot be excluded [AR1-ip-pool-vlan1]excluded-ip-address 192.168.1.2 192.168.1.10 --Specify the excluded address range [AR1-ip-pool-vlan1]excluded-ip-address 192.168.1.50 192.168.1.60 --Specify the excluded address range [AR1-ip-pool-vlan1]display this --Display the address pool configuration [V200R003C00] # ip pool vlan1 gateway-list 192.168.1.1 network 192.168.1.0 mask 255.255.255.0 excluded-ip-address 192.168.1.2 192.168.1.10 excluded-ip-address 192.168.1.50 192.168.1.60 lease day 0 hour 8 minute 0 dns-list 8.8.8.8 222.222.222.222 # Return

Configure the Vlanif 1 interface to select addresses from the global address pool. The vlan1 address pool created above is a global address pool.

[AR1]interface Vlanif 1 [AR1-Vlanif1]dhcp select global

A network segment is only able to create one address pool. If some addresses in the network segment are already occupied, they shall be excluded from the pool to avoid conflicts between the addresses assigned by the DHCP and other computers. The IP address and other configuration information assigned to the client by DHCP has a time limit (lease duration). If computers in the network changes frequently, the lease duration should be set shorter; and if the computers in the network are relatively stable, the lease duration should be set longer. Students in the School of Software are likely to change classrooms every two hours for lectures, so the lease duration can be set to 2 hours. Normally, the client will automatically find the DHCP server to renew the lease after half of the lease duration expires. If the duration expires and the client does not find the DHCP server to renew the lease, the DHCP server assumes the client is no longer in the network and its IP address will be retrieved and can be assigned to other computers later.

Create an address pool for the marketing department.

[AR1]ip pool vlan2 [AR1-ip-pool-vlan2]network 192.168.2.0 mask 24 [AR1-ip-pool-vlan2]gateway-list 192.168.2.1 [AR1-ip-pool-vlan2]dns-list 114.114.114.114 [AR1-ip-pool-vlan2]lease day 0 hour 2 minute 0 [AR1-ip-pool-vlan2]quit

Configure interface Vlanif 2 to select addresses from the global address pool.

[AR1]interface Vlanif 2 [AR1-Vlanif2]dhcp select global

Enter “display ip pool” to display the defined address pool.

<AR1>display ip pool ---------------------------------------------------------------- Pool-name : vlan1 Pool-No : 0 Position : Local Status : Unlocked Gateway-0 : 192.168.1.1 Mask : 255.255.255.0 VPN instance : -- ---------------------------------------------------------------- Pool-name : vlan2 Pool-No : 1 Position : Local Status : Unlocked Gateway-0 : 192.168.2.1 Mask : 255.255.255.0 VPN instance : -- IP address Statistic Total :506 Used :4 Idle :482 Expired :0 Conflict :0 Disable :20

Run the packet capture tool on Windows 10 and set the mode to obtain an IP address automatically to obtain IP addresses so that the packets the DHCP client uses to request an IP address can be captured. As shown in Fig. 11.5, you can see the four packets interacting between DHCP client and DHCP server, which is the working process of DHCP protocol.

Fig. 11.5
figure 5

The working process of DHCP protocol

Full size image

Enter “display ip pool name vlan1 used” to display the address lease usage of address pool vlan1. The two addresses that have been assigned to the computers are highlighted in bold below.

<AR1>display ip pool name vlan1 used    Pool-name     : vlan1  Pool-No       : 0  Lease         : 0 Days 8 Hours 0 Minutes  Domain-name   : -  DNS-server0   : 8.8.8.8           DNS-server1   : 222.222.222.222   NBNS-server0  : -                 Netbios-type  : -                 Position      : Local           Status           : Unlocked  Gateway-0     : 192.168.1.1       Mask          : 255.255.255.0  VPN instance  : -- ----------------------------------------------------------------          Start          End      Total   Used   Idle(Expired)   Conflict  Disable ----------------------------------------------------------------      192.168.1.1   192.168.1.254   253      2         231(0)         0        20 ----------------------------------------------------------------  Network section :  ---------------------------------------------------------------  Index        IP          MAC             Lease    Status   ---------------------------------------------------------------    252   192.168.1.253    5489-9851-4a95       335    Used   --Lease, with client MAC address    253   192.168.1.254    5489-9831-72f6       344     Used   --Lease, with client MAC address ---------------------------------------------------------------

11.4 Assign Addresses to Directly Connected Network Segments Using Interface Address Pool

The above operation configures the Huawei router as a DHCP server, creates an address pool for one network segment, and also assigns a network segment and subnet mask to the address pool. If the router assigns addresses for directly connected network segments, it is not necessary to create address pools. As the router port has been configured with address and subnet mask, you can use the network segment where the port is located as the network segment and subnet mask for the address pool.

As shown in Fig. 11.6, router AR1 is connected to two network segments 192.168.1.0/24 and 192.168.2.0/24. It is required to configure router AR1 to assign IP addresses to these two network segments.

Fig. 11.6
figure 6

Topology for assigning addresses to directly connected network segments using interface address pools

Full size image

Configure the addresses of interfaces GigabitEthernet 0/0/0 and GigabitEthernet 0/0/1 for AR1.

[AR1]interface GigabitEthernet 0/0/0 [AR1-GigabitEthernet0/0/0]ip address 192.168.1.1 24 [AR1-GigabitEthernet0/0/0]quit [AR1]interface GigabitEthernet 0/0/1 [AR1-GigabitEthernet0/0/1]ip address 192.168.2.1 24 [AR1-GigabitEthernet0/0/1]

Enable DHCP service and configure interface GigabitEthernet 0/0/0 to select addresses from the interface address pool.

[AR1]dhcp enable                                    --Enable global DHCP service [AR1]interface GigabitEthernet 0/0/0 [AR1-GigabitEthernet0/0/0]dhcp select interface     --Select an address from the interface address pool [AR1-GigabitEthernet0/0/0]dhcp server dns-list 114.114.114.114 [AR1-GigabitEthernet0/0/0]dhcp server ?             --You can view all configurations  dns-list             Configure DNS servers  domain-name          Configure domain name   excluded-ip-address  Mark disable IP addresses  ……  lease                Configure the lease of the IP pool [AR1-GigabitEthernet0/0/0]dhcp server excluded-ip-address 192.168.1.2 192.168.1.20     --Exclude the address

Configure interface GigabitEthernet 0/0/1 to select addresses from the interface address pool.

[AR1]interface GigabitEthernet 0/0/1     [AR1-GigabitEthernet0/0/1]dhcp select interface  [AR1-GigabitEthernet0/0/1]dhcp server dns-list 8.8.8.8     [AR1-GigabitEthernet0/0/1]dhcp server lease day 0 hour 4 minute 0

11.5 DHCP Relay

11.5.1 Principles of DHCP Relay

The previous part talks about DHCP server assigning IP addresses to directly connected network segments. DHCP server can also assign IP addresses to non-directly connected network segments. As shown in Fig. 11.7, AR1 is configured as a DHCP server to assign IP addresses to the R&D department. This requires enabling DHCP relay on interface Vlanif 1 of router AR2.

Fig. 11.7
figure 7

DHCP relay illustration

Full size image

The principles of DHCP relay are explained below.

  1. 1.

    When the DHCP client starts and performs DHCP initialization, it sends a DHCP Discover request message in the local network.

  2. 2.

    If a DHCP server exists in the local network, DHCP configuration can be directly performed without DHCP relay.

  3. 3.

    If there is no DHCP server in the local network, after receiving the broadcast message, the network device with DHCP relay function connected to this local network will process it appropriately and forward it to the DHCP server on the other network specified. As shown in Fig. 11.7, the DHCP relay forwards the DHCP request packet whose destination address is the IP address of the DHCP server, and the source address is the IP address of interface Vlanif 1 of AR2. DHCP is able to determine which network segment this request is from based on the source address.

  4. 4.

    DHCP server configures correspondingly according to the information provided by DHCP client, and sends the configuration information to DHCP client through DHCP relay to complete the dynamic configuration of DHCP client.

    In fact, several interaction processes like this are required from the beginning to the final completion of the configuration. The DHCP relay device modifies the corresponding fields in the DHCP message, changes the DHCP broadcast packets to unicast packets, and is responsible for the conversion between the server and the client.

11.5.2 Configure DHCP Relay for Cross-Network Segment Address Assignment

According to Fig. 11.7, the network environment is set up and the address pool remoteNet is created on router AR1 so as to assign addresses to the computers in the R&D department. The network of the R&D department is not directly connected to router AR1. The router isolates broadcasts, so AR1 cannot receive the DHCP discovery packets sent by the computers in the R&D department. This requires configuring interface Vlanif 1 of router AR2 to enable the DHCP relay function, which converts the received DHCP discovery packets into directed DHCP discovery packets with a destination address of 10.2.2.1 and a source address of 172.16.5.1, which is the address of the interface Vlanif 1. Once router AR1 receives such a packet, it knows that this is a request from network segment 172.16.5.0/24, so it selects an IP address from the address pool remoteNet for PC5. The prerequisite for completing this experiment is to ensure that these networks are unimpeded.

The following creates the address pool remoteNet on AR1 for the network of the R&D department. Gateways must be set for the address pool of the remote network segment.

[AR1]ip pool remoteNet [AR1-ip-pool-remoteNet]network 172.16.5.0 mask 24 [AR1-ip-pool-remoteNet]gateway-list 172.16.5.1           --Gateway must be set [AR1-ip-pool-remoteNet]dns-list 8.8.8.8     [AR1-ip-pool-remoteNet]lease day 0 hour 2 minute 0 [AR1-ip-pool-remoteNet]quit

Configure interface GE0/0/1 of AR1 to select an address from the global address pool.

[AR1]interface GigabitEthernet 0/0/1 [AR1-GigabitEthernet0/0/1]dhcp select global  [AR1-GigabitEthernet0/0/1]quit

Enable the DHCP function on router AR2, configure interface Vlanif 1 of router AR2, enable the DHCP relay function, and specify the address of the DHCP server.

[AR2]dhcp enable --Enable DHCP [AR2]interface Vlanif 1 [AR2-Vlanif1]dhcp select relay  --Enable DHCP relay on the interface [AR2-Vlanif1]dhcp relay server-ip 10.2.2.1 --Specify the address of the DHCP server

Set the address of PC5 to be dynamically assigned by DHCP, enter “ipconfig” to check the obtained IP address and verify the cross-network segment assignment. If it is unsuccessful, check the routing table on routers AR1 and AR2 to make sure the network is unobstructed for DHCP to assign IP addresses across network segments.

PC>ipconfig Link local IPv6 address...........: fe80::5689:98ff:fe61:65d IPv6 address......................: :: / 128 IPv6 gateway......................: :: IPv4 address......................: 172.16.5.254 Subnet mask.......................: 255.255.255.0 Gateway...........................: 172.16.5.1 Physical address..................: 54-89-98-61-06-5D DNS server........................: 8.8.8.8

11.6 Exercises

  1. 1.

    (Multi-selection) After deploying a DHCP server in the network, the administrator finds that some hosts obtain addresses that are not specified by the DHCP server. What are the possible reasons for this? ( )

    1. A.

      There is a more efficient DHCP server in the network

    2. B.

      Some hosts cannot communicate with the DHCP server normally, and the client system of these hosts automatically generates addresses in the range of 169.254.0.0

    3. C.

      Some hosts cannot communicate with the DHCP server normally, and the client system of these hosts automatically generates addresses in the range of 127.254.0.0

    4. D.

      The address pool of the DHCP server has been fully assigned

  2. 2.

    When the administrator configures the DHCP server, which of the following commands configures the shortest lease duration? ( )

    1. A.

      DHCP select

    2. B.

      Lease day 1

    3. C.

      Lease 24

    4. D.

      Lease 0

  3. 3.

    When the host reboots after obtaining an IP address from DHCP server A, which of the following messages will be sent to DHCP server A? ( )

    1. A.

      DHCP Discover

    2. B.

      DHCP Request

    3. C.

      DHCP Offer

    4. D.

      DHCP ACK

  4. 4.

    As shown in Fig. 11.8, which configuration needs to be done on Router RB to enable DHCP service on Router RA and create an address pool for network segment 192.168.3.0/24 so that PC2 can obtain an IP address from Router RA? ( )

    1. A.

      [RB]dhcp enable

      [RB]interface GigabitEthernet 0/0/0

      [RB-GigabitEthernet 0/0/0]dhcp select global

    2. B.

      [RB]dhcp enable

      [RB]interface GigabitEthernet 0/0/0

      [RB-GigabitEthernet 0/0/0]dhcp select relay

      [RB-GigabitEthernet 0/0/0]dhcp relay server-ip 192.168.2.1

    3. C.

      [RB]dhcp enable

      [RB]interface GigabitEthernet 0/0/1

      [RB-GigabitEthernet 0/0/0]dhcp select relay

      [RB-GigabitEthernet 0/0/0]dhcp relay server-ip 192.168.2.1

    4. D.

      [RB]interface GigabitEthernet 0/0/0

      [RB-GigabitEthernet 0/0/0]dhcp select relay

      [RB-GigabitEthernet 0/0/0]dhcp relay server-ip 192.168.2.1

  5. 5.

    (Multi-selection) What are the advantages of using DHCP to assign IP addresses? ( )

    1. A.

      IP addresses can be reused

    2. B.

      IP address conflicts can be avoided

    3. C.

      The workload is huge and it is difficult to manage

    4. D.

      When the configuration information changes (such as DNS), only the administrator needs to modify it on the DHCP server, which is convenient for unified management

  6. 6.

    What kind of DHCP message does a DHCP client send when it wants to leave the network? ( )

    1. A.

      DHCP Discover

    2. B.

      DHCP Release

    3. C.

      DHCP Request

    4. D.

      DHCP ACK

  7. 7.

    The priority of DHCP protocol interface address pool is higher than that of global address pool. This statement is ( ).

    1. A.

      Correct

    2. B.

      Incorrect

Fig. 11.8
figure 8

Communication illustration

Full size image