Cisco BPX 8650, Installation And Configuration Manual

Page: 430 / 606

24-4
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 24 Configuring BXM Virtual Trunks
How Virtual Trunking Works
How Virtual Trunking Works
The following is the syntax to describe a virtual trunk:
slot.port.vtrunk
The virtual trunk parameters are described in Table 24-1.
In general, the maximum number of virtual trunks that is configured per card equals the number of
virtual interfaces (VIs) provided by the card and how many are available for use. Each port, trunk or
virtual trunk interface requires the use of one VI. For example, the BXM supports 31 virtual interfaces;
therefore, up to a combination of 31 ports, trunks, and virtual trunks are configured on one BXM card.
Note A virtual trunk cannot be used as a feeder trunk. Feeder connections cannot be terminated on a virtual
trunk.
In Figure 24-2, three virtual trunks 4.1.1, 4.1.2, and 4.1.3 are shown configured on a physical trunk that
connects to the port 4.1 interface of a BXM. Also, a single trunk is shown configured on port 4.2 of the
BXM. In this example, four VIs are used, one each for virtual trunks 4.1, 4.2, and 4.3, and one for
physical trunk 4.2.
Figure 24-2 Virtual and Physical Trunks on a BXM
Each logical trunk, either physical or virtual, is assigned a virtual interface when it is activated.
A BXM card has 31 possible egress virtual interfaces. Each of these interfaces in turn has 16 Qbins
assigned to it.
In the example in Figure 24-3, port 1 has three virtual trunks (4.1.1, 4.1.2, and 4.1.3), each of which is
automatically assigned a virtual interface (VI) with the VI’s associated 16 Qbins. Port 2 is shown with
a single physical trunk (4.2) and is assigned a single VI.
Table 24-1 Virtual Trunk Parameters
Parameter Description
slot Specifies the slot number as 1 to 6 or 9 to 14. BPX slots 7 and 8 are
reserved for the BCC. Slot 15 is reserved for the ASM card.
port Specifies the port number to be 1 to 12. The port number depends on
the type of card.
vtrunk Specifies the virtual trunk number to be 1 to 31, on BXM, 1 to 32 on
BNI T3/E3, or 1 to 11 on BNI OC-3/STM1.
17720
Multiple logical trunks (virtual trunks)
Single logical trunk (physical trunk)
4.1.1
4.1.2
4.1.3
4.2