Example for Configuring Routed Proxy ARP

Overview

When an enterprise network is divided into subnets, two subnets may belong to the same network segment but different physical networks. These two subnets are isolated by the switch. You can modify the routing information about the hosts on the network, so that the data packets destined for other subnets are sent to the gateway connected to different subnets and then forwarded by the gateway to the destination. However, to implement this solution, you must configure routes for all hosts on the subnets. This complicates management and maintenance.

Deploying routed proxy ARP on the gateway can effectively solve the management and maintenance problems in subnet division. Routed proxy ARP allows the communication between the hosts whose IP addresses belong to the same network segment but different physical networks. In addition, the default gateway does not need to be configured on the hosts, facilitating management and maintenance.

Configuration Notes

After routed proxy ARP is enabled on the device, reduce the aging time of ARP entries on hosts. In this way, the invalid ARP entries do not take effect as soon as possible, reducing the number of packets that are sent to but cannot be forwarded by the switch.

Table 7-1 Applicable product models and versions

Series	Product Model	Software Version
S1700	S1720GFR	V200R006C10, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S1720GW and S1720GWR	V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S1720GW-E and S1720GWR-E	V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S1720X and S1720X-E	V200R011C00, V200R011C10, V200R012C00
S2700	S2700EI	V100R006C05
	S2710SI	V100R006C05
	S2720EI	V200R006C10, V200R009C00, V200R010C00, V200R011C10, V200R012C00
	S2750EI	V200R005C00SPC300, V200R006C00, V200R007C00, V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
S3700	S3700SI and S3700EI	V100R006C05
S3700	S3700HI	V200R001C00
S5700	S5700LI	V200R005C00SPC300, V200R006C00, V200R007C00, V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5700S-LI	V200R005C00SPC300, V200R006C00, V200R007C00, V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5700SI	V200R001C00, V200R002C00, V200R003C00, V200R005C00
	S5700EI	V200R001(C00&C01), V200R002C00, V200R003C00, V200R005(C00&C01&C02&C03)
	S5700HI	V200R001(C00&C01), V200R002C00, V200R003C00, V200R005(C00SPC500&C01&C02)
	S5710-C-LI	V200R001C00
	S5710-X-LI	V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5710EI	V200R001C00, V200R002C00, V200R003C00, V200R005(C00&C02)
	S5710HI	V200R003C00, V200R005(C00&C02&C03)
	S5720LI and S5720S-LI	V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5720SI and S5720S-SI	V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5720I-SI	V200R012C00
	S5720EI	V200R007C00, V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5720HI	V200R006C00, V200R007(C00&C10), V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S5730HI	V200R012C00
	S5730SI	V200R011C10, V200R012C00
	S5730S-EI	V200R011C10, V200R012C00
S6700	S6700EI	V200R001(C00&C01), V200R002C00, V200R003C00, V200R005(C00&C01&C02)
	S6720LI and S6720S-LI	V200R011C00, V200R011C10, V200R012C00
	S6720SI and S6720S-SI	V200R011C00, V200R011C10, V200R012C00
	S6720EI	V200R008C00, V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S6720S-EI	V200R009C00, V200R010C00, V200R011C00, V200R011C10, V200R012C00
	S6720HI	V200R012C00
S7700	S7703, S7706, and S7712	V200R001(C00&C01), V200R002C00, V200R003C00, V200R005C00, V200R006C00, V200R007C00, V200R008C00, V200R009C00, V200R010C00, V200R011C10, V200R012C00
S9700	S9703, S9706, and S9712	V200R001(C00&C01), V200R002C00, V200R003C00, V200R005C00, V200R006C00, V200R007(C00&C10), V200R008C00, V200R009C00, V200R010C00, V200R011C10, V200R012C00

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NOTE:

For details about software mappings, visit Hardware Query Tool and search for the desired product model.

Networking Requirements

As shown in Figure 7-2, branch A and branch B of the enterprise are located in different cities and their host IP addresses belong to the same network segment 172.16.0.0/16. There are reachable routes between Switch_1 connected to branch A and Switch_2 connected to branch B. Branch A and branch B belong to different broadcast domains; therefore, they cannot communicate on a LAN. Hosts in the branches are not configured with default gateway addresses, so they cannot communicate across network segments. The enterprise requires that branch A and branch B communicate without changing the host configurations.

Figure 7-2 Networking diagram for configuring routed proxy ARP
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Configuration Roadmap

The configuration roadmap is as follows:

Add the interface connecting Switch_1 and branch A to VLAN 10 and add the interface connecting Switch_2 and branch B to VLAN 20.
Enable routed proxy ARP on VLANIF interfaces of branch A and branch B to allow the two branches to communicate.

Procedure

Create VLANs, add interfaces to VLANs, and configure IP addresses for the interfaces.

# Configure Switch_1.

<HUAWEI> system-view
[HUAWEI] sysname Switch_1
[Switch_1] vlan batch 10
[Switch_1] interface gigabitethernet 1/0/1
[Switch_1-GigabitEthernet1/0/1] port link-type access
[Switch_1-GigabitEthernet1/0/1] port default vlan 10
[Switch_1-GigabitEthernet1/0/1] quit
[Switch_1] interface vlanif 10
[Switch_1-Vlanif10] ip address 172.16.1.1 24

# Configure Switch_2.

<HUAWEI> system-view
[HUAWEI] sysname Switch_2
[Switch_2] vlan batch 20
[Switch_2] interface gigabitethernet 1/0/1
[Switch_2-GigabitEthernet1/0/1] port link-type access
[Switch_2-GigabitEthernet1/0/1] port default vlan 20
[Switch_2-GigabitEthernet1/0/1] quit
[Switch_2] interface vlanif 20
[Switch_2-Vlanif20] ip address 172.16.2.1 24

Configure routed proxy ARP.

# Configure Switch_1.

[Switch_1-Vlanif10] arp-proxy enable  //Configure routed proxy ARP
[Switch_1-Vlanif10] quit

# Configure Switch_2.

[Switch_2-Vlanif20] arp-proxy enable  //Configure routed proxy ARP
[Switch_2-Vlanif20] quit

Verify the configuration.

# Check ARP entries of VLANIF 10 on Switch_1. The command output shows the MAC address mapping the IP address of VLANIF 10.

[Switch_1] display arp interface vlanif 10
IP ADDRESS      MAC ADDRESS     EXPIRE(M) TYPE        INTERFACE   VPN-INSTANCE                                                      
                                          VLAN/CEVLAN                                                                               
------------------------------------------------------------------------------                                                      
172.16.1.1      101b-5441-5bf6            I -         Vlanif10                                                                     
------------------------------------------------------------------------------                                                      
Total:1         Dynamic:0       Static:0     Interface:1

# Select Host_1 (using Windows 7 as an example) at 172.16.1.2/16 in branch A and select Host_2 at 172.16.2.2/16 in branch B. Ping the IP address of Host_2 on Host_1. The ping operation is successful.

C:\Documents and Settings\Administrator> ping 172.16.2.2
Pinging 172.16.2.2 with 32 bytes of data:
Reply from 172.16.2.2: bytes=32 time<1ms TTL=128
Reply from 172.16.2.2: bytes=32 time<1ms TTL=128
Reply from 172.16.2.2: bytes=32 time<1ms TTL=128
Reply from 172.16.2.2: bytes=32 time<1ms TTL=128

Ping statistics for 172.16.2.2:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

# Check the ARP table on Host_1. The command output shows that the MAC address mapping the IP address of Host_2 is the MAC address of VLANIF 10 on Switch_1, indicating that Host_1 and Host_2 can communicate with each other through ARP proxy.

C:\Documents and Settings\Administrator> arp -a
Interface: 172.16.1.2 --- 0xd
  Internet Address      Physical Address      Type
  172.16.2.2            101b-5441-5bf6        dynamic
...

Configuration Files

Switch_1 configuration file

#
sysname Switch_1
#
vlan batch 10
#
interface Vlanif10
 ip address 172.16.1.1 255.255.255.0
 arp-proxy enable
#
interface GigabitEthernet1/0/1
 port link-type access
 port default vlan 10
#
return

Switch_2 configuration file

#
sysname Switch_2
#
vlan batch 20
#
interface Vlanif20
 ip address 172.16.2.1 255.255.255.0
 arp-proxy enable
#
interface GigabitEthernet1/0/1
 port link-type access
 port default vlan 20
#
return

Example for Configuring Routed Proxy ARP