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NE20E-S2 V800R011C10 Configuration Guide - IP Services 02
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DNS Configuration

DNS Configuration

This chapter describes how to configure the domain name system (DNS) for network devices to communicate using domain names.

Overview of DNS

Domain Name System (DNS) is a distributed database for TCP/IP applications that provides conversion between domain names and IP addresses.

DNS uses a hierarchical naming method to specify a meaningful name for each device on the network and uses a resolver to establish mappings between IP addresses and domain names. DNS allows users to use meaningful and easy-to-memorize domain names instead of IP addresses to identify devices.

Limitations for DNS

Limitations

N/A

Configuring DNS Client

This section describes how to configure DNS and establish mappings between domain names and IP addresses, so that a device can communicate with other devices using domain names.

Usage Scenario

If you want to use meaningful and easy-to-memorize domain names to access other devices, configure DNS. DNS entries record the mappings between domain names and IP addresses. In Figure 6-1, the DNS client and client program are on the same device.
  • If you seldom use domain names to visit other devices or no DNS server is available, configure static DNS on the DNS client. To configure static DNS, you must know the mappings between domain names and IP addresses. If a mapping changes, you must manually modify the DNS entry on the DNS client.
  • If you want to use domain names to visit many devices and DNS servers are available, configure dynamic DNS on the DNS client. Dynamic DNS requires DNS servers.
Figure 6-1 Networking diagram for typical domain name resolution

Pre-configuration Tasks

Before configuring DNS, complete the following tasks:

  • Configuring a route between the DNS client and server, so that the DNS client and server can communicate

  • Configuring DNS servers

Procedure

  • Configure static DNS.

    1. Run system-view

      The system view is displayed.

    2. Run ip host [ vpn-instance vpn-name ]

      The mapping between the domain name and IPv4 address of the host is configured.

    3. Run commit

      The configuration is committed.

  • Configure dynamic DNS.

    1. Run system-view

      The system view is displayed.

    2. Run dns resolve

      Dynamic DNS is enabled.

    3. Run dns server ip-address [ vpn-instance vpn-name ]

      A DNS server is specified.

    4. (Optional) Run dns server source-ip source-ip-address [ vpn-instance vpn-name ]

      An IP address is specified for the DNS client to communicate with the DNS server. Using a specified source address ensures the security of communication between the DNS client and DNS server.

    5. Run dns domain domain-name [ vpn-instance vpn-name ]

      A domain name suffix is added.

    6. (Optional) Run dns timeout interval-time

      A DNS query response timeout period is configured.

    7. (Optional) Run dns try times

      The number of retransmission times for DNS query packets is configured.

    8. Run commit

      The configuration is committed.

    To configure multiple DNS servers, repeatedly perform Step 3. To configure multiple domain name suffixes, repeatedly perform Step 5.

Verifying the Configuration of a DNS Client

After configuring a DNS client, verify the configuration.

  • Run the display ip host command to view static DNS entries, including mappings between domain names and IP addresses.

  • Run the display dns server command to view the IP addresses of all configured DNS servers.

  • Run the display dns domain command to view the domain name suffix list.

  • Run the display dns dynamic-host command to view dynamic DNS entries stored in the cache.

Maintaining DNS

This chapter describes how to maintain DNS, which includes clearing dynamic DNS entries and monitoring the DNS running status.

Clearing Dynamic DNS Entries

This section describes how to clear dynamic DNS entries using a reset command.

Context

The dynamic DNS entries cannot be restored after they are cleared. Exercise caution when running the reset command.

Procedure

  1. After confirming the dynamic DNS entries to be deleted from the cache, run the reset dns dynamic-host [ vpn-instance vpn-name ] command in the user view.

Monitoring the DNS Running Status

This section describes how to monitor the DNS running status.

Context

In routine maintenance, you can run the following commands in all views to check the running status of DNS.

Procedure

  • Run the display ip host [ vpn-instance vpn-name ] command to check information about the static domain name resolution table.
  • Run the display dns server(IPv4) [ vpn-instance vpn-name ] command to check DNS server configurations.
  • Run the display dns domain(IPv4) [ vpn-instance vpn-name ] command to check domain name suffixes.
  • Run the display dns dynamic-host [ vpn-instance vpn-name ] command to check information about dynamic DNS entries in the cache.

Configuration Examples for DNS

Each configuration example consists of the networking requirements, configuration roadmap, configuration procedures, and configuration files.

Example for Configuring Static DNS

This section describes how to configure static DNS.

Networking Requirements

As shown in Figure 6-2, Device A frequently uses the domain name "host.com" to visit the host. To improve the efficiency of domain name resolution, you can establish a static mapping between the domain name "host.com" and IP address 10.100.1.2 in the static domain name resolution table of Device A.

Figure 6-2 Configuring static DNS

Configuration Roadmap

The configuration roadmap is as follows:

  • Establish a static mapping between the domain name "host.com" and IP address 10.100.1.2 on Device A.

Data Preparation

To complete the configuration, you need the following data:

  • IP addresses of Device A and the host

  • Domain name of the host

Procedure

  1. Configure a static mapping between the domain name "host.com" and IP address 10.100.1.2.

    <HUAWEI> system-view
    [~HUAWEI]sysname DeviceA
    [*HUAWEI]commit
    [~DeviceA] ip host host.com 10.100.1.2
    [*DeviceA] commit

  2. Verify the configuration.

    # Run the ping host.com command on Device A. The host can be pinged. The destination IP address for the ping operation is 10.100.1.2.
    <DeviceA> ping host.com
      ping host.com (10.100.1.2):56 data bytes, press CTRL_C to break
     Reply from 10.100.1.2: bytes=56 Sequence=1 ttl=128 time=1 ms
     Reply from 10.100.1.2: bytes=56 Sequence=2 ttl=128 time=4 ms
     Reply from 10.100.1.2: bytes=56 Sequence=3 ttl=128 time=3 ms
     Reply from 10.100.1.2: bytes=56 Sequence=4 ttl=128 time=2 ms
     Reply from 10.100.1.2: bytes=56 Sequence=5 ttl=128 time=3 ms

    --- host.com ping statistics ---
     5 packet(s) transmitted
     5 packet(s) received
     0.00% packet loss
     round-trip min/avg/max = 1/2/4 ms
    # Run the display ip host command on Device A to check static DNS entry information, including mappings between domain names and IP addresses.
    <DeviceA> display ip host
    Host                 Age        Flags  Address
host.com             0          static 10.100.1.2

Configuration Files

  • Device A configuration file

    #
 sysname DeviceA
#
 ip host host.com 10.100.1.2
#
return

Example for Configuring Dynamic DNS Client

This section describes how to configure dynamic DNS.

Networking Requirements

As shown in Figure 6-3, Device A serves as the DNS client. With the help of the DNS server, Device A can use the domain name "huawei.com" to access the host with IP address 10.2.1.3/16.

Figure 6-3 Networking diagram for dynamic DNS

Interfaces 1 through 2in this example are GE 0/1/0, GE 0/1/1 respectively.



Configuration Roadmap

The configuration roadmap is as follows:

  1. Enable dynamic DNS.

  2. Configure the IP address of the DNS server.

  3. Configure a domain name suffix.

Data Preparation

To complete the configuration, you need the following data:

  • Domain names of Device B and Device C

  • IP address of the DNS server

  • Domain name suffixes

Procedure

  1. Configure Device A.

    # Configure dynamic DNS entries.

    <HUAWEI> system-view
    [~HUAWEI]sysname DeviceA
    [*HUAWEI]commit

    # Enable dynamic DNS.

    [~DeviceA] dns resolve

    # Configure the IP address of the DNS server.

    [*DeviceA] dns server 10.3.1.2

    # Configure a domain name suffix "net".

    [*DeviceA] dns domain net

    # Configure a domain name suffix "com".

    [*DeviceA] dns domain com
    [*DeviceA] commit
    [~DeviceA] quit

    To implement domain name resolution, you must configure a route between Device A and the DNS server for them to communicate. For details about how to configure a route, see NE20EUniversal Service Router Configuration Guide - IP Routing.

  2. Verify the configuration.

    # Run the ping huawei command on Device A. The host with domain name "huawei.com" can be pinged. The destination IP address for the ping operation is 10.2.1.3.

    <DeviceA> ping huawei.com
      PING huawei.com (10.2.1.3): 56  data bytes, press CTRL_C to break
        Reply from 10.2.1.3: bytes=56 Sequence=1 ttl=126 time=6 ms
        Reply from 10.2.1.3: bytes=56 Sequence=2 ttl=126 time=4 ms
        Reply from 10.2.1.3: bytes=56 Sequence=3 ttl=126 time=4 ms
        Reply from 10.2.1.3: bytes=56 Sequence=4 ttl=126 time=4 ms
        Reply from 10.2.1.3: bytes=56 Sequence=5 ttl=126 time=4 ms

      --- huawei.com ping statistics ---
        5 packet(s) transmitted
        5 packet(s) received
        0.00% packet loss
        round-trip min/avg/max = 4/4/6 ms

    # Run the display dns dynamic-host command on Device A. Dynamic DNS entry information stored in the cache is displayed.

    <DeviceA> display dns dynamic-host
    No  Domain Name           IpAddress            TTL       Alias
    1   huawei.com            10.2.1.3             3579

    TTL indicates how long a DNS entry can exist, in seconds.

Configuration Files

  • Configuration file of Device A

    #
     sysname DeviceA
    #
     dns resolve
     dns server 10.3.1.2
     dns domain net
     dns domain com
    #
    interface GigabitEthernet0/1/0
     undo shutdown
     ip address 1.1.1.2 255.255.0.0
    #
    rip 1
     network 1.0.0.0
    #
    return

  • Configuration file of Device B

    #
     sysname DeviceB
    #
    interface GigabitEthernet0/1/0
     undo shutdown
     ip address 2.1.1.1 255.255.0.0
    #
    interface GigabitEthernet0/1/1
     undo shutdown
     ip address 1.1.1.1 255.255.0.0
    #
    interface LoopBack0
     ip address 4.1.1.1 255.255.255.255
    #
    rip 1
     network 2.0.0.0
    network 1.0.0.0
     network 4.0.0.0
    #
    return

  • Configuration file of Device C

    #
     sysname DeviceC
    #
    interface GigabitEthernet0/1/0
     undo shutdown
     ip address 2.1.1.2 255.255.0.0
    #
    interface GigabitEthernet0/1/1
     undo shutdown
     ip address 3.1.1.1 255.255.0.0
    #
    interface LoopBack0
     ip address 4.1.1.2 255.255.255.255
    #
    rip 1
     network 2.0.0.0
     network 3.0.0.0
    network 4.0.0.0
    #
    return
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Updated: 2020-02-07

Document ID: EDOC1100125470

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