Cisco BPX 8650, Руководство по установке и настройке

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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 1 The BPX Switch: Functional Overview
BPX Switch Operation
Virtual Trunking
Virtual trunking provides the ability to define multiple trunks within a single physical trunk port
interface. Virtual trunking benefits include the following:
•
Reduced cost by configuring the virtual trunks supplied by the public carrier for as much bandwidth
as needed instead of at full T3, E3, or OC-3 bandwidths.
•
Utilization of the full mesh capability of the public carrier to reduce the number of leased lines
needed between nodes in the Cisco WAN switching networks.
•
Choice of keeping existing leased lines between nodes, but using virtual trunks for backup.
• Ability to connect BNI or BXM trunk interfaces to a public network using standard ATM UNI cell
format.
•
Virtual trunking is provisioned through either a Public ATM Cloud or a Cisco WAN switching ATM
cloud.
A virtual trunk may be defined as a “trunk over a public ATM service.” The trunk really doesn’t exist as
a physical line in the network. Rather, an additional level of reference, called a
virtual trunk number ,
is used to differentiate the virtual trunks found within a physical trunk port.
Figure 1-8 shows four Cisco WAN switching networks, each connected to a Public ATM Network
through a physical line. The Public ATM Network is shown linking all four of these subnetworks to every
other one with a full meshed network of virtual trunks. In this example, each physical line is configured
with three virtual trunks.
Figure 1-8 Virtual Trunking Example
Cisco
sub-network
Cisco
sub-network
Cisco
sub-network
Cisco
sub-network
Public ATM
Network
ATM-UNI ATM-UNI
ATM-UNI ATM-UNI
Virtual trunk
Leased line
H8227
Leased line
(backup)