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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.10, Part Number 78-11603-01 Rev. D0, July 2001
Chapter 24 Configuring BXM Virtual Trunks
Overview
Note A virtual trunk cannot be used as a feeder trunk. Feeder connections cannot be terminated
on a virtual trunk.
This syntax describes a virtual trunk:
UXM/BXM:slot.port.vtrunk
slot = slot number (1–32) Keep in mind that on the BPX slots 7 and 8 are reserved for BCCs and slot
and 15 is reserved for the ASM card.
port = port number (1–16)
vtrunk = virtual trunk number (1–31 on BXM) (1–15 on UXM)
Card Capacities
These three principles define card capacities for virtual trunking:
• The maximum number of virtual trunks that may be configured per card equals the number of
virtual interfaces (VIs).
• Valid virtual trunk numbers are 1 through 31 per port.
• The maximum number of virtual trunks is limited to the number of virtual interfaces (VIs) available
on the card and each logical trunk (physical or virtual) utilizes one VI.
For example, the BXM supports 31 virtual interfaces and therefore up to 31 virtual trunks may be
defined within one port.
Thus maximum capacities are:
• Each BPX node can have a combined maximum of 64 logical (physical and virtual) trunks per node.
• Each IGX node can have a combined maximum of 32 logical (physical and virtual) trunks per node.
• A BNI-T3 or E3 line can support up to 32 virtual trunks on one or both physical ports.
• A BNI-OC-3 line can support up to 11 virtual trunks.
• A BXM card can support up to 31 virtual trunks.
• A UXM card can support up to 15 virtual trunks.
Trunk Redundancy
Trunk redundancy refers to one of two features:
• SONET Automatic Protection Switching (APS)
With Release 9.2, APS line redundancy is supported. APS line redundancy is available only on
BXM SONET trunks and is compatible with virtual trunks. The trunk port supporting virtual trunks
may have APS line redundancy configured in the same way it would be configured for a physical
Table 24-1 Virtual Trunk Criteria
Number of VIs Max LCNs Default LCNs
BXM 31 32000 16320