21
S
HARED
VLAN C
ONFIGURATION
Shared VLAN
Overview
Shared VLAN is special VLAN which is created based on I/O Modules of the device.
It is designed to avoid packet broadcast in the applications of selective QinQ.
Generation of Shared
VLAN
Like a QinQ-enabled port, a port with the selective QinQ enabled also learns the
source MAC addresses of user packets to the MAC address table of the default
VLAN of the port. However, the port with selective QinQ enabled can insert an
outer VLAN tag besides the default VLAN tag to the packets. Thus, when packets
from the service provider to customers are forwarded, broadcast arises because
each of these packets fails to find its destination MAC address in the MAC table of
its outer VLAN.
Figure 48
Learn MAC addresses of selective QinQ frames
As shown in Figure 48, when user packets are received, the default VLAN of the
incoming port is VLAN 2, and the incoming port is specified to receive packets of
VLAN 3, with outer tag of VLAN 4. When a packet is received, its source MAC
address MAC-A is learned into the MAC address table of the default VLAN (VLAN
2) of the port.
When a response packet is returned to the device from VLAN 4 of the service
provider network, the device will search the outgoing port for MAC-A in the MAC
address table of VLAN 4. However, because the corresponding entry is not learned
into the MAC address table of VLAN 4, this packet is considered to be a unicast
packet with unknown destination MAC address. As a result, this packet will be
broadcast to all the ports in VLAN 4, which wastes the network resources and
endangers the network.
The problem above can be solved by using the shared VLAN feature, which
summarizes the MAC address tables of all the VLANs. The switch can find the
outgoing port for a packet according to the MAC address table of the shared
VLAN and unicast the packet.
VLAN3
MAC-A
VLAN4
MAC-A
PVID=2
Private
Network
Public
Network
Private
Network
Public
Network
PVID=2
VLAN4
MAC-A
Receives the data that the
private network sends to the
service provider
ÿ
s network
Receives the data that the
service provider
ÿ
s network
sends to the private network
Summary of Contents for Switch 7757
Page 32: ...32 CHAPTER 1 CLI OVERVIEW...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION...
Page 126: ...126 CHAPTER 14 SUPER VLAN...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION...
Page 718: ...718 CHAPTER 63 CLUSTER...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING...