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Example for Configuring a DHCP Relay Agent (Connected to a DHCP Server over a GRE Tunnel)

Networking Requirements

In Figure 1, an enterprise deploys its headquarters and branch in different areas. To enable the headquarters and branch to communicate through the Internet, a Generic Routing Encapsulation (GRE) tunnel needs to be deployed. To facilitate unified management, a DHCP server needs to be configured on Switch_1 in the headquarters to assign IP addresses to the terminals in the headquarters and branch. The network segments 10.1.1.0/24 and 10.2.1.0/24 are planned for the headquarters and branch, respectively.

Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731S-H, S5731-S, S5731S-S, S6720-HI, S5732-H, S6730-H, S6730S-H, S6730-S, S6730S-S, S6720-EI, and S6720S-EI support GRE.

Figure 1 Networking diagram for configuring a DHCP server to allocate IP addresses to clients through a GRE tunnel

Configuration Roadmap

The configuration roadmap is as follows:

  1. Run OSPF between Switch_1, Switch_2, and Switch_3 to ensure their reachability.

  2. On Switch_1 and Switch_3, configure tunnel interfaces and create a GRE tunnel.

  3. Configure Switch_1 as a DHCP server based on a global address pool so that the DHCP server can assign IP addresses from the global address pool to the terminals in the headquarters and branch.

  4. Configure Switch_3 as a DHCP relay and to function as the branch's gateway to forward DHCP messages between the terminals and DHCP server.

Huawei S series switch functions as a DHCP server (Switch_1) in this example.

Configure the interface link types and VLANs on LSW_1 and LSW_2 to implement Layer 2 communication.

Procedure

  1. Configure an IP address for each physical interface on Switch_1 through Switch_3.

    # Configure Switch_1.

    <HUAWEI> system-view
[HUAWEI] sysname Switch_1
[Switch_1] vlan batch 10 30
[Switch_1] interface gigabitethernet 0/0/1
[Switch_1-GigabitEthernet0/0/1] port link-type trunk
[Switch_1-GigabitEthernet0/0/1] port trunk allow-pass vlan 10
[Switch_1-GigabitEthernet0/0/1] quit
[Switch_1] interface gigabitethernet 0/0/2
[Switch_1-GigabitEthernet0/0/2] port link-type trunk
[Switch_1-GigabitEthernet0/0/2] port trunk allow-pass vlan 30
[Switch_1-GigabitEthernet0/0/2] quit
[Switch_1] interface vlanif 10
[Switch_1-Vlanif10] ip address 192.168.20.1 24
[Switch_1-Vlanif10] quit
[Switch_1] interface vlanif 30
[Switch_1-Vlanif30] ip address 10.1.1.1 24
[Switch_1-Vlanif30] quit

    # Configure Switch_2.

    <HUAWEI> system-view
[HUAWEI] sysname Switch_2
[Switch_2] vlan batch 10 20
[Switch_2] interface gigabitethernet 0/0/1
[Switch_2-GigabitEthernet0/0/1] port link-type trunk
[Switch_2-GigabitEthernet0/0/1] port trunk allow-pass vlan 10
[Switch_2-GigabitEthernet0/0/1] quit
[Switch_2] interface gigabitethernet 0/0/2
[Switch_2-GigabitEthernet0/0/2] port link-type trunk
[Switch_2-GigabitEthernet0/0/2] port trunk allow-pass vlan 20
[Switch_2-GigabitEthernet0/0/2] quit
[Switch_2] interface vlanif 10
[Switch_2-Vlanif10] ip address 192.168.20.2 24
[Switch_2-Vlanif10] quit
[Switch_2] interface vlanif 20
[Switch_2-Vlanif20] ip address 192.168.30.1 24
[Switch_2-Vlanif20] quit

    # Configure Switch_3.

    <HUAWEI> system-view
[HUAWEI] sysname Switch_3
[Switch_3] vlan batch 20 30
[Switch_3] interface gigabitethernet 0/0/1
[Switch_3-GigabitEthernet0/0/1] port link-type trunk
[Switch_3-GigabitEthernet0/0/1] port trunk allow-pass vlan 20
[Switch_3-GigabitEthernet0/0/1] quit
[Switch_3] interface gigabitethernet 0/0/2
[Switch_3-GigabitEthernet0/0/2] port link-type trunk
[Switch_3-GigabitEthernet0/0/2] port trunk allow-pass vlan 30
[Switch_3-GigabitEthernet0/0/2] quit
[Switch_3] interface vlanif 20
[Switch_3-Vlanif20] ip address 192.168.30.2 24
[Switch_3-Vlanif20] quit
[Switch_3] interface vlanif 30
[Switch_3-Vlanif30] ip address 10.2.1.1 24
[Switch_3-Vlanif30] quit

  2. Run OSPF between Switch_1, Switch_2, and Switch_3.

    # Configure Switch_1.

    [Switch_1] ospf 1
[Switch_1-ospf-1] area 0
[Switch_1-ospf-1-area-0.0.0.0] network 192.168.20.0 0.0.0.255
[Switch_1-ospf-1-area-0.0.0.0] quit
[Switch_1-ospf-1] quit

    # Configure Switch_2.

    [Switch_2] ospf 1
[Switch_2-ospf-1] area 0
[Switch_2-ospf-1-area-0.0.0.0] network 192.168.20.0 0.0.0.255
[Switch_2-ospf-1-area-0.0.0.0] network 192.168.30.0 0.0.0.255
[Switch_2-ospf-1-area-0.0.0.0] quit
[Switch_2-ospf-1] quit

    # Configure Switch_3.

    [Switch_3] ospf 1
[Switch_3-ospf-1] area 0
[Switch_3-ospf-1-area-0.0.0.0] network 192.168.30.0 0.0.0.255
[Switch_3-ospf-1-area-0.0.0.0] quit
[Switch_3-ospf-1] quit

  3. Configure tunnel interfaces.

    # Configure Switch_1.

    [Switch_1] interface tunnel 1
[Switch_1-Tunnel1] tunnel-protocol gre
[Switch_1-Tunnel1] ip address 192.168.40.1 24
[Switch_1-Tunnel1] source 192.168.20.1
[Switch_1-Tunnel1] destination 192.168.30.2
[Switch_1-Tunnel1] quit

    # Configure Switch_3.

    [Switch_3] interface tunnel 1
[Switch_3-Tunnel1] tunnel-protocol gre
[Switch_3-Tunnel1] ip address 192.168.40.2 24
[Switch_3-Tunnel1] source 192.168.30.2
[Switch_3-Tunnel1] destination 192.168.20.1
[Switch_3-Tunnel1] quit

  4. Configure Switch_1 as a DHCP server.

    # Enable DHCP. By default, the service is disabled.

    [Switch_1] dhcp enable

    # Create a global address pool and configure related parameters.

    [Switch_1] ip pool pool1
[Switch_1-ip-pool-pool1] network 10.2.1.0 mask 255.255.255.0
[Switch_1-ip-pool-pool1] gateway-list 10.2.1.1
[Switch_1-ip-pool-pool1] quit
[Switch_1] ip pool pool2
[Switch_1-ip-pool-pool2] network 10.1.1.0 mask 255.255.255.0
[Switch_1-ip-pool-pool2] gateway-list 10.1.1.1
[Switch_1-ip-pool-pool2] quit
    # Configure the terminals connected to VLANIF30 to obtain IP addresses from the global address pool.
    [Switch_1] interface vlanif 30
[Switch_1-Vlanif30] dhcp select global
[Switch_1-Vlanif30] quit
    # Configure a static route to the network segment of the terminals in the branch.
    [Switch_1] ip route-static 10.2.1.0 255.255.255.0 tunnel 1

  5. Configure the DHCP relay function on Switch_3.

    # Enable DHCP. By default, the service is disabled.

    [Switch_3] dhcp enable
    # Configure the DHCP relay function on VLANIF 30 and specifies the DHCP server address for the relay.
    [Switch_3] interface vlanif 30
[Switch_3-Vlanif30] dhcp select relay 
[Switch_3-Vlanif30] dhcp relay server-ip 10.1.1.1
[Switch_3-Vlanif30] quit
    # Configure a static route to the network segment of the server.
    [Switch_3] ip route-static 10.1.1.0 255.255.255.0 tunnel 1

  6. Configure each terminal (using a PC running Windows 7 as an example) to automatically obtain an IP address.

    # Right-click Network and choose Properties to display the Network and Sharing Center window.

    # Click Local Area Connection to display the Local Area Connection Status window.

    # Click Properties to display the Local Area Connection Properties window.

    # Select Internet Protocol Version 4 (TCP/IPv4) and click Properties to display the Internet Protocol Version 4 (TCP/IPv4) Properties window.

    # Select Obtain an IP address automatically and click OK.

  7. Verify the configuration.

    # Run the display dhcp relay interface vlanif 30 command on Switch_3 to check the DHCP relay configuration.

    [Switch_3] display dhcp relay interface vlanif 30
 DHCP relay agent running information of interface Vlanif30 :
 Server IP address [00] : 10.1.1.1
 Gateway address in use : 10.2.1.1

    # Run the display ip pool command on Switch_1 to check the IP address allocation of pool1 and pool2. The headquarters in this example has 100 terminals while the branch has 50.

    [Switch_1] display ip pool name pool1
  Pool-name        : pool1
  Pool-No          : 0
  Lease            : 1 Days 0 Hours 0 Minutes
  Domain-name      : -
  DNS-server0      : -
  NBNS-server0     : -
  Netbios-type     : -
  Position         : Local
  Status           : Unlocked
  Gateway-0        : 10.2.1.1
  Network          : 10.2.1.0
  Mask             : 255.255.255.0
  VPN instance     : --
  Logging          : Disable
  Conflicted address recycle interval: -
  Address Statistic: Total       :253       Used        :50
  Idle        :203       Expired     :0
  Conflict    :0         Disabled     :0

 -------------------------------------------------------------------------------
  Network section
         Start           End       Total    Used Idle(Expired) Conflict Disabled
 -------------------------------------------------------------------------------
        10.2.1.1      10.2.1.254     253      50        203(0)       0     0
 -------------------------------------------------------------------------------
    [Switch_1] display ip pool name pool2 
  Pool-name        : pool2
  Pool-No          : 1
  Lease            : 1 Days 0 Hours 0 Minutes
  Domain-name      : -
  DNS-server0      : -
  NBNS-server0     : -
  Netbios-type     : -
  Position         : Local
  Status           : Unlocked
  Gateway-0        : 10.1.1.1
  Network          : 10.1.1.0
  Mask             : 255.255.255.0
  VPN instance     : --
  Logging          : Disable
  Conflicted address recycle interval: -
  Address Statistic: Total       :253       Used        :50
  Idle        :203       Expired     :0
  Conflict    :0         Disabled     :0

 -------------------------------------------------------------------------------
  Network section
         Start           End       Total    Used Idle(Expired) Conflict Disabled
 -------------------------------------------------------------------------------
        10.1.1.1      10.1.1.254     253     100        153(0)       0     0
 -------------------------------------------------------------------------------

Configuration Files

  • Switch_1 configuration file

    #
sysname Switch_1
#
vlan batch 10 30
#
dhcp enable
# 
ip pool pool1
 gateway-list 10.2.1.1
 network 10.2.1.0 mask 255.255.255.0
# 
ip pool pool2
 gateway-list 10.1.1.1
 network 10.1.1.0 mask 255.255.255.0
# 
interface Vlanif10
 ip address 192.168.20.1 255.255.255.0
#
interface Vlanif30
 ip address 10.1.1.1 255.255.255.0
 dhcp select global
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 10
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 30
#
interface Tunnel1
 ip address 192.168.40.1 255.255.255.0
 tunnel-protocol gre
 source 192.168.20.1
 destination 192.168.30.2
#
ospf 1
 area 0.0.0.0
  network 192.168.20.0 0.0.0.255
#
ip route-static 10.2.1.0 255.255.255.0 Tunnel1
#
return

  • Switch_2 configuration file

    #
sysname Switch_2
#
vlan batch 10 20
#
interface Vlanif10
 ip address 192.168.20.2 255.255.255.0
#
interface Vlanif20
 ip address 192.168.30.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 10
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 20
#
ospf 1
 area 0.0.0.0
  network 192.168.20.0 0.0.0.255
  network 192.168.30.0 0.0.0.255
#
return

  • Switch_3 configuration file

    #
sysname Switch_3
#
vlan batch 20 30
#
dhcp enable
# 
interface Vlanif20
 ip address 192.168.30.2 255.255.255.0
#
interface Vlanif30
 ip address 10.2.1.1 255.255.255.0
 dhcp select relay
 dhcp relay server-ip 10.1.1.1  
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 20
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 30
#
interface Tunnel1
 ip address 192.168.40.2 255.255.255.0
 tunnel-protocol gre
 source 192.168.30.2
 destination 192.168.20.1
#
ospf 1
 area 0.0.0.0
  network 192.168.30.0 0.0.0.255
#
ip route-static 10.1.1.0 255.255.255.0 Tunnel1
#
return
Parent Topic: Configuration Examples for DHCP
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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