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Network design
292 Avaya Application Solutions IP Telephony Deployment Guide
Trunk configuration
A trunk port on an Ethernet switch is one that is capable of forwarding Ethernet frames on
multiple VLANs through the mechanism of VLAN tagging. IEEE 802.1Q specifies the standard
method for VLAN tagging. Cisco also uses a proprietary method called ISL. Avaya products do
not interoperate with ISL.
A trunk link is a connection between two devices across trunk ports. This connection can be
between a router and a switch, between two switches, or between a switch and an IP
Telephone. Some form of trunking or forwarding multiple VLANs must be enabled to permit the
IP Telephone and the attached personal computer to appear on separate VLANs. The
commands in Table 51
enable trunking.
Note that Cisco and Avaya can remove VLANs from a trunk port. This is a highly desirable
feature because only two VLANs at most should appear on a trunk port that is connected to an
IP Telephone. That is, broadcasts from nonessential VLANs should not be permitted to bog
down the link to the IP Telephone.
VLAN binding feature (C360)
The default behavior of trunking is to permit all VLANs. In addition, the port does not need to be
a trunk at all to forward multiple VLANs.
To enable VLAN binding:
1. Verify that the port is configured with the desired port VLAN or native VLAN.
2. Add additional VLANs with one of the following VLAN-binding-mode options:
Static option
a. Put the port in bind-to-static mode by typing set port vlan-binding-mode <mod/port>
static.
b. Statically add another VLAN in addition to the port VLAN or the native VLAN by typing
set port static-vlan <mod/port> <vid>.
Configured option
c. Add a VLAN to the configured VLAN list by typing set vlan <id>.
d. Type show vlan to see entire list.
Table 51: Administration commands for VLAN trunking
Avaya C360 Cisco CatOS
set trunk <mod/port> dot1q
By default, all VLANs (1 to 3071)
are enabled on the trunk port.
VLANs can be specified using
VLAN binding commands.
set trunk <mod/port> nonegotiate dot1q
By default, all VLANs (1 to1005) are enabled
on the trunk port. VLANs can be selectively
removed with the command clear trunk
<mod/port> <vid>.