Figure 3-12
Networking diagram of Layer 3 communications between different sub-
VLANs based on Proxy ARP
VLAN 3
VLAN 2
Super VLAN 10
VLANIF10: 10.1.1.1/24
Host A
10.1.1.2/24
Host B
10.1.1.3/24
Eth2/0/1
Eth2/0/2
Suppose that the ARP table of Host A has no corresponding entry of Host B, and the gateway
is enabled with the Proxy ARP between sub-VLANs. Then the communication process
between Host A in VLAN 2 and Host B in VLAN 3 is shown as below:
1.
After comparing the IP address of Host B 10.1.1.3 with its IP address, Host A finds
that both IP addresses are in the same network segment 10.1.1.0/24, and its ARP table
has no corresponding entry of Host B.
2.
Host A initiates an ARP broadcast to request for the MAC address of Host B.
3.
Host is not in the broadcast domain of VLAN 2, and cannot receive the ARP request.
4.
The gateway is enabled with the Proxy ARP between sub-VLANs. Therefore, after
receiving the ARP request from Host A, the gateway finds that the IP address of
Host B 10.1.1.3 is the IP address of a directly-connected interface. Then the gateway
initiates an ARP broadcast to all the other sub-VLAN interfaces to request for the
MAC address of Host B.
5.
After receiving the ARP request, Host B offers an ARP response.
6.
After receiving the ARP response from Host B, the gateway replies its MAC address
to Host A.
7.
The ARP tables in both the gateway and Host A have the corresponding entries of
Host B.
8.
To send packets to Host B, Host A first sends packets to the gateway, and then the
gateway performs the Layer 3 forwarding.
The process that Host B sends packets to Host A is just the same, and is not mentioned
here.
l
Layer 2 Communications Between a Sub-VLAN and an External Network
, in the Layer 2 VLAN communications based on ports, the
received or sent frames are not tagged with the super-VLAN ID.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
3 VLAN Configuration
Issue 01 (2014-11-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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