Cisco BPX 8600 Series, Руководство по установке и настройке

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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001
Chapter 25 Configuring BXM Virtual Trunks
Overview
passed transparently through to the other end. The VCI bits within the header are passed transparently
through the entire cloud (see Figure 25-1). The virtual path ID (VPI) is provided by the ATM cloud
administrator (for example, service provider).
The BXM card’s physical trunk interface to the ATM cloud is a standard ATM UNI or NNI interface at
the cloud’s access point. The administrator of the ATM cloud (such as, Service Provider) specifies
whether the interface is UNI or NNI, and also provides the VPI to be used by a virtual trunk across the
cloud. Specifying an NNI cell interface provides 4 more bits of VPI addressing space.
There are two general types of virtual trunks:
•
AutoRoute Virtual Trunks
These are PVP or SPVP connections that carry AutoRoute PVC connections.
• VSI Virtual Trunks
These are PVP or SPVP connections that carry MPLS or PNNI connections. VSI Virtual Trunks
and MPLS Virtual Trunks differ in a number of ways including the way in which their endpoints
are configured.
Typical ATM Hybrid Network with Virtual Trunks
With the BPX switch, you can set up virtual networks with either the Broadband Network Interface
(BNI) card or with the BXM card. The virtual trunks originate and terminate on:
•
BXMs to BXMs;
or
• BXMs to UXMs (IGX switch);
or
• BNIs to BNIs
•
But not
BNIs to BXMs or UXMs.
When the Cisco network port is a BXM accessing a port in the Public ATM network, the Public ATM
port may be a UNI or NNI port on a BXM or other standards-compliant UNI or NNI port.
When the Cisco network port is a BNI accessing a port in the Public ATM network, the Public ATM
port must be a port on a BPX.
Figure 25-1 shows three Cisco WAN switching networks, each connected to a Public ATM Network via
a physical line. The Public ATM Network is shown linking all three of these subnetworks to every other
one with a full meshed network of virtual trunks. In this example, each physical line is configured with
two virtual trunks.