Chapter 28: MAC Address-based VLANs
310
Section VI: Virtual LANs
Egress Ports
Implementing a MAC address-based VLAN involves more than entering
the MAC addresses of the end nodes that are members of the VLAN. You
must also designate the egress ports on the switch for the packets from
the nodes. The egress ports define the limits of flooding of packets when a
port receives a unicast packet with an unknown destination address (that
is, an address that has not been learned by the MAC address table).
Without knowing the egress ports, the switch would be forced to flood the
packets on all switch ports, and that could result in a security violation
where end nodes receive packets from other nodes that are in different
VLANs.
Table 89 illustrates a simple example of the mapping of addresses to
egress ports for a MAC address-based VLAN of 6 nodes. The example
consists of four workstations, a printer, and a server. For instance,
Workstation 1 is connected to port 1 on the switch and is mapped to
egress ports 5 for the server and 6 for the printer.
Obviously, mapping source MAC addresses to egress ports can become
cumbersome if you are dealing with a MAC address-based VLAN that
encompasses a large number of ports and nodes. Fortunately, the egress
ports of a VLAN are considered as a community and, as such, need only
be designated as an egress port of one address in the VLAN to be
considered an egress port of all the addresses.
For instance, referring to the previous example, if workstation 1 sends a
packet containing an unknown destination MAC address, the switch does
not flood the packet to just ports 5 and 6, even though those are the
designated egress ports for packets from workstation 1. Rather, it floods it
out all egress ports assigned to all the MAC addresses of the VLAN,
except, of course, the port where the packet was received. In the example
the switch would flood the packet out ports 2 through 6.
Table 89. Mappings of MAC Addresses to Egress Ports Example
MAC address
End Node
Switch Egress
Port
00:30:84:54:1A:45
Workstation 1 (Port 1)
5, 6
00:30:84:C3:5A:11
Workstation 2 (Port 2)
5, 6
00:30:84:22:67:17
Workstation 3 (Port 3)
5, 6
00:30:84:78:75:1C
Workstation 4 (Port 4)
5, 6
00:30:79:7A:11:10
Server (Port 5)
1-4
00:30:42:53:10:3A
Printer (Port 6)
1-4
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 ...