Huawei AR530 Series - Page 93

l Sub-interface
As shown in Figure 3-8, DeviceA is a Layer 3 switch supporting sub-interface, and
DeviceB is a Layer 2 switch. LANs are connected using the switched Ethernet interface on
DeviceB and the routed Ethernet interface on DeviceA. User hosts are assigned to VLAN2
and VLAN3. To implement inter-VLAN communication, configure as follows:
– On DeviceA, create two sub-interfaces Port1.1 and Port2.1 on the Ethernet interface
connecting to DeviceB, and configure 802.1Q encapsulation on sub-interfaces
corresponding to VLAN2 and VLAN3.
– Configure IP addresses for sub-interfaces.
– Set types of Ethernet interfaces connecting DeviceB and DeviceA to Trunk or
Hybrid, to allow VLAN2 and VLAN3 frames.
– Set the default gateway address to the IP address of the sub-interface mapping the VLAN
to which the user host belongs.
Figure 3-8 Inter-VLAN communication using sub-interfaces
DeviceB
VLAN2
VLAN3
VLAN Trunk
Port1.1
Access port
DeviceA
Host A Host DHost C
Host B
Port2.1
Host A communicates with host C as follows:
1. Host A checks the IP address of host C and determines that host C is in another VLAN.
2. Host A sends an ARP request packet to DeviceA to request DeviceA's MAC address.
3. After receiving the ARP request packet, DeviceA returns an ARP reply packet in
which the source MAC address is the MAC address of the sub-interface mapping
VLAN2.
4. Host A obtains DeviceA's MAC address.
5. Host A sends a packet whose destination MAC address is the MAC address of the
sub-interface and destination IP address is host C's IP address to DeviceA.
6. After receiving the packet, DeviceA forwards the packet and detects that the route to
host C is a direct route. The packet is forwarded by the sub-interface mapping VLAN3.
7. Functioning as the gateway of hosts in VLAN3, DeviceA broadcasts an ARP packet
requesting host C's MAC address.
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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