AT-S63 Management Software Features Guide
Section VI: Virtual LANs
311
The community characteristic of egress ports relieves you from having to
map each address to its corresponding egress port. You only need to be
sure that all the egress ports in a MAC address-based VLAN are assigned
to at least one address.
It is also important to note that a MAC address must be assigned at least
one egress port to be considered a member of a MAC address-based
VLAN. VLAN membership of packets from a source MAC address not
assigned any egress ports is determined by the PVID of the port where the
packets are received.
Because egress ports are considered as a community within a VLAN, you
can simplify the mappings by assigning all of the egress ports to just one
MAC address and, for the rest of the addresses, assigning just one port.
This will make it easier to add or delete MAC addresses or egress ports
from a VLAN. Here is how the example might look.
A switch can support more than one MAC-address VLAN at a time and a
port can be an egress member of more than one VLAN. While this can
prove useful in some situations, it can also result in VLAN leakage where
the traffic of one VLAN crosses the boundary into other VLANs.
The problem arises in the case of unknown unicast traffic. If the switch
receives a packet from a member of a MAC address-based VLAN with an
unknown destination address, it floods the packet on all egress ports of the
VLAN. If the VLAN contains a port that is also serving as an egress port of
another VLAN, the node connected to the port receives the flooded
packets, even if it does not belong to the same VLAN as the node that
generated the packet.
Here’s an example. Assume that Port 4 on a switch has been designated
an egress port of three MAC address-based VLANs. Any unknown unicast
traffic that the switch receives that belongs to any of the VLANs will be
flooded out Port 4, even if there are no active members of that particular
VLAN on the port. This means that whatever device is connected to the
port receives the flooded traffic of all three VLANs.
Table 90. Revised Example of Mappings of MAC Addresses to Egress Ports
MAC Address
End Node
Egress Port
00:30:84:54:1A:45
Workstation 1 (Port 1)
1-6
00:30:84:C3:5A:11
Workstation 2 (Port 2)
1
00:30:84:22:67:17
Workstation 3 (Port 3)
1
00:30:84:78:75:1C
Workstation 4 (Port 4)
1
00:30:79:7A:11:10
Server (Port 5)
1
00:30:42:53:10:3A
Printer (Port 6)
1
Summary of Contents for AT-S63
Page 14: ...Figures 14 ...
Page 18: ...Tables 18 ...
Page 28: ...28 Section I Basic Operations ...
Page 58: ...Chapter 1 Overview 58 ...
Page 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Page 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Page 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Page 116: ...116 Section II Advanced Operations ...
Page 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Page 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Page 196: ...196 Section III Snooping Protocols ...
Page 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Page 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Page 218: ...218 Section IV SNMPv3 ...
Page 234: ...234 Section V Spanning Tree Protocols ...
Page 268: ...268 Section VI Virtual LANs ...
Page 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Page 320: ...320 Section VII Internet Protocol Routing ...
Page 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Page 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Page 372: ...372 Section VIII Port Security ...
Page 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Page 404: ...404 Section IX Management Security ...
Page 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Page 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Page 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Page 532: ...Appendix D MIB Objects 532 ...