Access Vlans - Cisco 7604-RSP720C-R Configuration Manual

Chapter 3 Configuring Layer 2 Interfaces
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m
method allows packets that are encapsulated for several different VLANs to traverse the same port and
maintain traffic separation between the VLANs. Also, the encapsulated VLAN tag allows the trunk to
move traffic end-to-end through the network on the same VLAN.
Figure 3-2 Header Without and With 802.1Q Tag
Start
Preamble Frame
(7 - bytes) Delimiter
(1 - byte)
Dest.
Start
MAC
Preamble Frame
Address
(7-bytes) Delimiter
(6-bytes) (6-bytes)
(1-byte)

Access VLANs

If you assign an access VLAN that is also a primary VLAN for a private VLAN, all access ports with
Note
that access VLAN will also receive all the broadcast traffic for the primary VLAN in the private VLAN
mode.
See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x, for
Note
complete information on private VLANs.
When you configure a port in access mode, you can specify which VLAN will carry the traffic for that
interface. If you do not configure the VLAN for a port in access mode, or an access port, the interface
carries traffic for the default VLAN (VLAN1).
You can change the access port membership in a VLAN by specifying the new VLAN. You must create
the VLAN before you can assign it as an access VLAN for an access port. If you change the access
VLAN on an access port to a VLAN that is not yet created, the system shuts that access port down.
If an access port receives a packet with an 802.1Q tag in the header other than the access VLAN value,
that port drops the packet without learning its MAC source address.
OL-23435-03
Dest. Source
Length
MAC MAC
/ Type
Address Address
(2 -
(6 - (6 -
bytes)
bytes) bytes)
Source
Length/Type
MAC
= 802.1Q
Address
Tag Type
(2-byte)
3 bits = User Priority field
1 bit = Canonical Format Identifier (CFI)
12 bits – VLAN Identifier (VLAN ID)
Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x
MAC Client Data
(0 - n bytes)
Length
Tag
MAC Client
/Type
Control
Data
(2-
Information
(0-n bytes)
(2-bytes) bytes)
Information About Access and Trunk Interfaces
Frame
Pad
Check
(0 - p
Sequence
bytes)
(4 - bytes)
Frame
Pad
Check
(0-p
Sequence
bytes)
(4-bytes)
3-5