2-2
You can solve the problem by enabling proxy ARP on Switch. After that, Switch can reply to the ARP
request from Host A with the MAC address of VLAN-interface 1, and forward packets sent from Host A
to Host B. In this case, Switch seems to be a proxy of Host B.
A main advantage of proxy ARP is that it is added on a single router without disturbing routing tables of
other routers in the network. Proxy ARP acts as the gateway for IP hosts that are not configured with a
default gateway or do not have routing capability.
Local Proxy ARP
As shown in Figure 2-2, Host A and Host B belong to VLAN 2, but are isolated at Layer 2. Host A
connects to GigabitEthernet 1/0/3 while Host B connects to GigabitEthernet 1/0/1. Enable local proxy
ARP on Switch to allow Layer 3 communication between the two hosts.
Figure 2-2 Application environment of local proxy ARP
Switch
Vlan-int2
192.168.10.100/24
Switch
GE1/0/3
GE1/0/1
GE1/0/2
Host A
192.168.10.99/24
Host B
192.168.10.200/24
VLAN 2
port-isolate group
In one of the following cases, you need to enable local proxy ARP:
z Hosts connecting to different isolated Layer 2 ports in the same VLAN need to communicate at
Layer 3.
z If an isolate-user-vlan is configured, hosts in different secondary VLANs of the isolate-user-vlan
need to communicate at Layer 3.
Enabling Proxy ARP
Follow these steps to enable proxy ARP in VLAN interface view:
To do… Use the command… Remarks
Enter system view
system-view
—
Enter interface view
interface interface-type interface-number
Required
Enable proxy ARP
proxy-arp enable
Required
Disabled by default.
Follow these steps to enable local proxy ARP in VLAN interface view:
To do… Use the command… Remarks
Enter system view
system-view
—
Enter interface view
interface interface-type interface-number
Required
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