H3C S12500R Switch Router Series
GRE Tunneling Between DHCP Relay and DHCP Server Configuration Examples

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The information in this document is subject to change without notice.

 

Contents

Introduction· 1

Prerequisites· 1

Restrictions and guidelines· 1

Example: Interconnecting DHCP relay and DHCP server with GRE tunnels· 2

Network configuration· 2

Analysis· 3

Applicable hardware and software versions· 3

Restrictions and guidelines· 3

Procedures· 3

Configuring Device A· 4

Configuring Device B· 5

Configuring Device C· 6

Configuring Switch A· 8

Configuring Switch B· 8

Verifying the configuration· 9

Configuration file· 10

Device A· 10

Device B· 11

Device C· 11

Switch A· 13

Switch B· 13

Related documentation· 13

 

Introduction

When the DHCP client and the DHCP server are located on different physical networks, the client can obtain IP addresses and other configuration information from the server through DHCP relay.

DHCP relay simplifies and facilitates network management. With this feature, you can achieve centralized DHCP server configuration and management by configuring the DHCP server function on devices at the core layer or configuring dedicated DHCP servers in the DHCP server area. You do not need to configure the DHCP server function on each device (user gateway) at the convergence layer.

When the DHCP relay and the DHCP server are in different areas, you can interconnect them with VPN tunnels (such as GRE and MPLS VPN tunnels) across the WAN.

This document introduces a configuration example of interconnecting DHCP relay and DHCP server with GRE tunnels.

Prerequisites

The configuration examples were created and verified in a lab environment, and all the devices were started with the factory default configuration. When you are working on a live network, make sure you understand the potential impact of every command on your network. If you have configured the devices before performing this configuration task, make sure that the existing configuration does not conflict with the configuration in the following example.

The following information is provided based on the assumption that you have basic knowledge of DHCP, OSPF, and GRE.

Restrictions and guidelines

By default, interfaces on the device are disabled (in ADM or Administratively Down state). To have an interface operate, you must use the undo shutdown command to enable that interface.

Some physical interfaces in this example must operate in bridge (Layer 2) mode. By default, the physical interfaces on the device operate in routed (Layer 3) mode. To change the link mode of a physical interface, use the port link-mode command.

Example: Interconnecting DHCP relay and DHCP server with GRE tunnels

Network configuration

As shown in the following figure, Device A is the headquarters gateway of an organization and Device C is the branch gateway. Device A, Device B, and Device C are interconnected over IPv4 networks. Specific network requirements are as follows:

·     The headquarters and the branch can access each other through GRE tunnels

·     Device A acts as the DHCP server and Device C acts as the DHCP relay. Device A can assign IP addresses to endpoints at the branch and the headquarters.

·     Device A, Device B, and Device C run OSPF to ensure that they can reach each other.

Figure 1 Network diagram

 

Device	Interface	IP address
Device A	Vlan-int10	192.168.10.1/24
	Vlan-int20	192.168.20.1/24
	Tunnel 1	192.168.100.1/24
Device B	Vlan-int20	192.168.20.2./24
	Vlan-int30	192.168.30.1/24
Device C	Vlan-int30	192.168.30.2/24
	Vlan-int10	192.168.40.1/24
	Tunnel 1	192.168.100.2/24

‌

Analysis

1.     Run OSPF on Device A, Device B, and Device C to ensure that they can reach each other.

2.     Configure tunnel interfaces on Device A and Device C, and then configure a GRE tunnel to connect the two devices.

3.     Enable the DHCP server function on Device A, so it can assign IP addresses from the global address pool to endpoints at the headquarters and the branch.

4.     Configure the DHCP relay function on Device C, so endpoints at the branch can exchange DHCP messages with the DHCP server for IP address acquisition.

5.     Configure static routes destined for the headquarters network and the branch network, because only Device A, Device B, and Device C run OSPF.

Applicable hardware and software versions

The following matrix shows the hardware and software versions to which this configuration example is applicable:

 

Hardware	Software version
S12500R switch series	Release 5210 and later

 

Restrictions and guidelines

·     Both ends of the GRE tunnel must be configured with source and destination addresses. The source address and destination address configured on the local end must be the same as the destination address and source address configured on the remote end, respectively.

·     Encapsulated packets cannot be forwarded twice at Layer 3 based on destination address and routing table. To resolve this issue, send encapsulated packets to the service loopback group, which will then return those packets to the forwarding module for Layer 3 forwarding. Therefore, to achieve tunnel packet reception and transmission, you need to create a tunnel-type service loopback group.

Procedures

The following configuration steps assume that all device interfaces are routed ports by default.

Configuring Device A

Configuring VLANs and assigning IP addresses to VLAN interfaces

<DeviceA> system-view

[DeviceA] vlan 10 20

[DeviceA] interface vlan-interface 10

[DeviceA-Vlan-interface10] ip address 192.168.10.1 24

[DeviceA-Vlan-interface10] quit

[DeviceA] interface vlan-interface 20

[DeviceA-Vlan-interface20] ip address 192.168.20.1 24

[DeviceA-Vlan-interface20] quit

[DeviceA] interface hundredgige 1/0/1

[DeviceA-HundredGigE1/0/1] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceA-HundredGigE1/0/1] port link-type trunk

[DeviceA-HundredGigE1/0/1] port trunk permit vlan 10

[DeviceA-HundredGigE1/0/1] quit

[DeviceA] interface hundredgige 1/0/2

[DeviceA-HundredGigE1/0/2] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceA-HundredGigE1/0/2] port link-type trunk

[DeviceA-HundredGigE1/0/2] port trunk permit vlan 20

[DeviceA-HundredGigE1/0/2] quit

Enabling OSPF

# Configure a unique global router ID for Device A.

 

NOTE: Devices in the same AS must use different global router Ids. To ensure that the router ID of a router is unique in the AS, specify the IP address of an interface on that router as the router ID.

 

[DeviceA] router id 192.168.10.1

# Configure a network for an OSPF area and enable OSPF on the interfaces attached to the specified network.

[DeviceA] ospf 1

[DeviceA-ospf-1] area 0

[DeviceA-ospf-1-area-0.0.0.0] network 192.168.20.0 0.0.0.255

[DeviceA-ospf-1-area-0.0.0.0] quit

[DeviceA-ospf-1] quit

Configuring GRE tunnels

# Create service loopback group 1 and configure its service type as tunnel.

[DeviceA] service-loopback group 1 type tunnel

# Add HundredGigE 1/0/3 into service loopback group 1.

[DeviceA] interface hundredgige 1/0/3

[DeviceA-HundredGigE1/0/3] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceA-HundredGigE1/0/3] port service-loopback group 1

All configurations on the interface will be lost. Continue?[Y/N]:y

[DeviceA-HundredGigE1/0/3] quit

# Create tunnel interface Tunnel1 and specify it tunnel mode as GRE over IPv4.

[DeviceA]interface Tunnel 1 mode gre

# Configure an IP address for tunnel interface Tunnel1

[DeviceA-Tunnel1] ip address 192.168.100.1 24

# Specify a source address for the GRE tunnel.

[DeviceA-Tunnel1] source 192.168.20.1

# Specify a destination address for the GRE tunnel.

[DeviceA-Tunnel1] destination 192.168.30.2

[DeviceA-Tunnel1] quit

Configuring Device A as the DHCP server

# Enable VLAN-interface 10 to operate in DHCP server mode.

[DeviceA] interface vlan-interface 10

[DeviceA-Vlan-interface10] dhcp select server

[DeviceA-Vlan-interface10] quit

# Configure DHCP address pool 1 for IP address assignment to endpoints at the branch.

[DeviceA] dhcp server ip-pool 1

[DeviceA-dhcp-pool-1] network 192.168.40.0 24

[DeviceA-dhcp-pool-1] gateway-list 192.168.40.1

[DeviceA-dhcp-pool-1] quit

# Configure DHCP address pool 2 for IP address assignment to endpoints at the headquarters.

[DeviceA] dhcp server ip-pool 2

[DeviceA-dhcp-pool-2] network 192.168.10.0 24

[DeviceA-dhcp-pool-2] gateway-list 192.168.10.1

[DeviceA-dhcp-pool-2] quit

# Enable DHCP.

[DeviceA] dhcp enable

Configuring a static route destined for the branch network

[DeviceA] ip route-static 192.168.40.0 24 Tunnel 1

Configuring Device B

Configuring VLANs and assigning IP addresses to VLAN interfaces

<DeviceB> system-view

[DeviceB] vlan 20 30

[DeviceB] interface Vlan-interface 20

[DeviceB-Vlan-interface20] ip address 192.168.20.2 24

[DeviceB-Vlan-interface20] quit

[DeviceB] interface Vlan-interface 30

[DeviceB-Vlan-interface30] ip address 192.168.30.1 24

[DeviceB-Vlan-interface30] quit

[DeviceB] interface hundredgige 1/0/1

[DeviceB-HundredGigE1/0/1] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceB-HundredGigE1/0/1] port link-type trunk

[DeviceB-HundredGigE1/0/1] port trunk permit vlan 20

[DeviceB-HundredGigE1/0/1] quit

[DeviceB] interface hundredgige 1/0/2

[DeviceB-HundredGigE1/0/2] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceB-HundredGigE1/0/2] port trunk permit vlan 30

[DeviceB-HundredGigE1/0/2] quit

Enabling OSPF

# Configure a unique global router ID for Device B.

[DeviceB] router id 192.168.30.1

# Configure networks for an OSPF area and enable OSPF on the interfaces attached to the specified networks.

[DeviceB] ospf 1

[DeviceB-ospf-1] area 0

[DeviceB-ospf-1-area-0.0.0.0] network 192.168.20.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] network 192.168.30.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] quit

[DeviceB-ospf-1] quit

Configuring Device C

Configuring VLANs and assigning IP addresses to VLAN interfaces

<DeviceC> system-view

[DeviceC] vlan 10 30

[DeviceC] interface Vlan-interface 10

[DeviceC-Vlan-interface10] ip address 192.168.40.1 24

[DeviceC-Vlan-interface10] quit

[DeviceC] interface Vlan-interface 30

[DeviceC-Vlan-interface30] ip address 192.168.30.2 24

[DeviceC-Vlan-interface30] quit

[DeviceC] interface hundredgige 1/0/1

[DeviceC-HundredGigE1/0/1] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceC-HundredGigE1/0/1] port link-type trunk

[DeviceC-HundredGigE1/0/1] port trunk permit vlan 30

[DeviceC-HundredGigE1/0/1] quit

[DeviceC] interface hundredgige 1/0/2

[DeviceC-HundredGigE1/0/2] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceC-HundredGigE1/0/2] port link-type trunk

[DeviceC-HundredGigE1/0/2] port trunk permit vlan 10

[DeviceC-HundredGigE1/0/2] quit

Enabling OSPF

# Configure a unique global router ID for Device C.

[DeviceC] router id 192.168.40.1

# Configure a network for an OSPF area and enable OSPF on the interfaces attached to the specified network.

[DeviceC] ospf 1

[DeviceC-ospf-1] area 0

[DeviceC-ospf-1-area-0.0.0.0] network 192.168.30.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] quit

[DeviceC-ospf-1] quit

Configuring GRE tunnels

# Create service loopback group 1 and configure its service type as tunnel.

[DeviceC] service-loopback group 1 type tunnel

# Add HundredGigE 1/0/3 into service loopback group 1.

[DeviceC] interface hundredgige 1/0/3

[DeviceC-HundredGigE1/0/3] port link-mode bridge

The configuration of the interface will be restored to the default. Continue? [Y/N]:y

[DeviceC-HundredGigE1/0/3] port service-loopback group 1

All configurations on the interface will be lost. Continue?[Y/N]:y

[DeviceC-HundredGigE1/0/3] quit

# Create tunnel interface Tunnel1 and specify it tunnel mode as GRE over IPv4.

[DeviceC] interface Tunnel 1 mode gre

# Configure an IP address for tunnel interface Tunnel1

[DeviceC-Tunnel1] ip address 192.168.100.2 24

# Specify a source address for the GRE tunnel.

[DeviceC-Tunnel1] source 192.168.30.2

# Specify a destination address for the GRE tunnel.

[DeviceC-Tunnel1] destination 192.168.20.1

[DeviceC-Tunnel1] quit

Configuring Device B as the DHCP relay

# Enable VLAN-interface 10 to operate in DHCP relay mode.

[DeviceC] interface vlan-interface 10

[DeviceC-Vlan-interface10] dhcp select relay

# Specify DHCP server address 192.168.10.1 on VLAN-interface 10.

[DeviceC-Vlan-interface10] dhcp relay server-address 192.168.10.1

[DeviceC-Vlan-interface10] quit

# Enable DHCP.

[DeviceC] dhcp enable

# Enable recording client information in relay entries.

[DeviceC] dhcp relay client-information record

Configuring a static route destined for the headquarters network.

[DeviceC] ip route-static 192.168.10.0 24 Tunnel 1

Configuring Switch A

# Create VLAN 10.

<SwitchA> system-view

[SwitchA] vlan 10

[SwitchA-vlan10] quit

# Configure the endpoint-facing interface. In this example, HundredGigE 1/0/1 that connects Switch A to Host A is used.

[SwitchA] interface hundredgige 1/0/1

[SwitchA-HundredGigE1/0/1] port access vlan 10

[SwitchA-HundredGigE1/0/1] quit

# Configure the gateway-facing interface. In this example, HundredGigE 1/0/2 that connects Switch A to the headquarters gateway (Device A) is used.

[SwitchA]interface hundredgige 1/0/2

[SwitchA-HundredGigE1/0/2] port link-type trunk

[SwitchA-HundredGigE1/0/2] port trunk permit vlan 10

[SwitchA-HundredGigE1/0/2] quit

Configuring Switch B

# Create VLAN 10.

<SwitchB> system-view

[SwitchB] vlan 10

[SwitchB-vlan10] quit

# Configure the endpoint-facing interface. In this example, HundredGigE 1/0/1 that connects Switch B to Host B is used.

[SwitchB] interface hundredgige 1/0/1

[SwitchB-HundredGigE1/0/1] port access vlan 10

[SwitchB-HundredGigE1/0/1] quit

# Configure the gateway-facing interface. In this example, HundredGigE 1/0/2 that connects Switch B to the branch gateway (Device C) is used.

[SwitchB]interface hundredgige 1/0/2

[SwitchB-HundredGigE1/0/2] port link-type trunk

[SwitchB-HundredGigE1/0/2] port trunk permit vlan 10

[SwitchB-HundredGigE1/0/2] quit

Verifying the configuration

# View the IP addresses assigned by Device A.

<DeviceA> display dhcp server ip-in-use

IP address       Client-identifier/    Lease expiration      Type

                 Hardware address

192.168.10.2     0037-3866-302e-3137-  Oct  8 10:46:47 2023  Auto(C)

                 3461-2e30-3430-362d-

                 4745-302f-302f-31

192.168.40.2     0037-3866-302e-3161-  Oct  8 11:02:24 AM 2023  Auto(C)

                 3138-2e30-3530-362d-

                 4745-302f-302f-31

# View the relay entries on Device C.

<DeviceC> display dhcp relay client-information

Total number of client-information items: 1

Total number of dynamic items: 1

Total number of temporary items: 0

IP address       MAC address      Type        Interface            VPN name

192.168.40.2     78f0-1a18-0506   Dynamic     Vlan10               N/A

# Verify that users at the headquarters can access those at the branch.

[HostA] ping 192.168.40.2

Ping 192.168.40.2 (192.168.40.2): 56 data bytes, press CTRL+C to break

56 bytes from 192.168.40.2: icmp_seq=0 ttl=253 time=4.000 ms

56 bytes from 192.168.40.2: icmp_seq=1 ttl=253 time=3.000 ms

56 bytes from 192.168.40.2: icmp_seq=2 ttl=253 time=2.000 ms

56 bytes from 192.168.40.2: icmp_seq=3 ttl=253 time=3.000 ms

56 bytes from 192.168.40.2: icmp_seq=4 ttl=253 time=2.000 ms

 

--- Ping statistics for 192.168.40.2 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 2.000/2.800/4.000/0.748 ms

# Verify that users at the branch can access those at the headquarters.

[HostB] ping 192.168.10.2

Ping 192.168.10.2 (192.168.10.2): 56 data bytes, press CTRL+C to break

56 bytes from 192.168.10.2: icmp_seq=0 ttl=253 time=4.000 ms

56 bytes from 192.168.10.2: icmp_seq=1 ttl=253 time=2.000 ms

56 bytes from 192.168.10.2: icmp_seq=2 ttl=253 time=3.000 ms

56 bytes from 192.168.10.2: icmp_seq=3 ttl=253 time=2.000 ms

56 bytes from 192.168.10.2: icmp_seq=4 ttl=253 time=4.000 ms

 

--- Ping statistics for 192.168.10.2 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 2.000/3.000/4.000/0.894 ms

Configuration file

Device A

#

 service-loopback group 1 type tunnel

#

 router id 192.168.10.1

#

ospf 1

 area 0.0.0.0

  network 192.168.20.0 0.0.0.255

#

 dhcp enable

#

vlan 1

#

vlan 10

#

vlan 20

#

dhcp server ip-pool 1

 gateway-list 192.168.40.1

 network 192.168.40.0 mask 255.255.255.0

#

dhcp server ip-pool 2

 gateway-list 192.168.10.1

 network 192.168.10.0 mask 255.255.255.0

#

interface Vlan-interface10

 ip address 192.168.10.1 255.255.255.0

#

interface Vlan-interface20

 ip address 192.168.20.1 255.255.255.0

#

interface HundredGigE1/0/1

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 10

#

interface HundredGigE1/0/2

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 20

#

interface HundredGigE1/0/3

 port link-mode bridge

 port service-loopback group 1

#

interface Tunnel1 mode gre

 ip address 192.168.100.1 255.255.255.0

 source 192.168.20.1

 destination 192.168.30.2

#

 ip route-static 192.168.40.0 24 Tunnel1

#

Device B

#

 router id 192.168.30.1

#

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

#

vlan 1

#

vlan 20

#

vlan 30

#

interface Vlan-interface20

 ip address 192.168.20.2 255.255.255.0

#

interface Vlan-interface30

 ip address 192.168.30.1 255.255.255.0

#

interface HundredGigE1/0/1

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 20

#

interface HundredGigE1/0/2

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 30

#

Device C

#

 service-loopback group 1 type tunnel

#

 router id 192.168.40.1

#

ospf 1

 area 0.0.0.0

  network 192.168.30.0 0.0.0.255

#

 dhcp enable

 dhcp relay client-information record

#

vlan 1

#

vlan 10

#

vlan 30

#

interface Vlan-interface10

 ip address 192.168.40.1 255.255.255.0

 dhcp select relay

 dhcp relay server-address 192.168.10.1

#

interface Vlan-interface30

 ip address 192.168.30.2 255.255.255.0

#

interface HundredGigE1/0/1

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 30

#

interface HundredGigE1/0/2

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 10

#

interface HundredGigE1/0/3

 port link-mode bridge

 port service-loopback group 1

#

interface Tunnel1 mode gre

 ip address 192.168.100.2 255.255.255.0

 source 192.168.30.2

 destination 192.168.20.1

#

 ip route-static 192.168.10.0 24 Tunnel1

#

Switch A

#

vlan 1

#

vlan 10

#

interface HundredGigE1/0/1

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 10

#

interface HundredGigE1/0/2

 port link-mode bridge

 port access vlan 10

#

Switch B

#

vlan 1

#

vlan 10

#

interface HundredGigE1/0/1

 port link-mode bridge

 port link-type trunk

 port trunk permit vlan 1 10

#

interface HundredGigE1/0/2

 port link-mode bridge

 port access vlan 10

#

Related documentation

·     Layer 3—IP Services Configuration Guide in H3C S12500R Switch Router Series Configuration Guides-R52xx

·     Layer 3—IP Services Command Reference in H3C S12500R Switch Router Series Command References-R52xx

·     Layer 3—IP Services Configuration Guide in H3C S12500R-48Y8C&S12500R-48C6D Switch Router Configuration Guides-R52xx

·     Layer 3—IP Services Command Reference in H3C S12500R-48Y8C&S12500R-48C6D Switch Router Command References-R52xx