Users Guide

144 Network Administration: VLAN
FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Dell Astute\User
Guide\Dell_Astute_Network_Admin_VLAN.fm
DELL CONFIDENTIAL – PRELIMINARY 8/9/16 - FOR PROOF ONLY
Frame Flow
Figure 9-1 describes the flow of VLAN frames from the Ingress port to the
Egress port:
Figure 9-1. Frame Flow Through a VLAN
When a frame is received, it must be assigned a VLAN. VLAN assignment is
accomplished by the following steps:
1
If the frame contains a VLAN tag, that tag is used, otherwise the frame is
classified by the port's default VLAN (PVID), if it is defined.
2 After classification, the frame may pass (if enabled) through ingress
filtering, where the frame is dropped if the frame's VLAN ID is not one of
the VLANs to which the ingress port belongs.
3 A forwarding decision is made, as a function of the VLAN ID and the
destination MAC address.
4 The egress rules define whether the frame is to be sent as tagged or
untagged.
Special-case VLANs
VLAN#1 and VLAN#4095 are special-case VLANs:
• VLAN — Defined as the default VLAN. This means that if the VLAN,
whose VID is the current port's PVID, is deleted from the port (or from the
system), that port's PVID is set to 1. VLAN#1 cannot be deleted from the
system.
•
VLAN4095 — Defined (according to standard and industry practice) as
the discard VLAN. A frame classified to this VLAN is silently dropped.
Ingress Egress
VLAN
Classification
Ingr ess
Filtering
Egress
Filtering
Progress
Forwarding
Decision
Filtering
Database
Received
Frame
Transmitted
Frame
Ingress Egress
VLAN
Classification
Ingr ess
Filtering
VLAN
Classification
Ingr ess
Filtering
Egress
Filtering
Progress
Forwarding
Decision
Filtering
Database
Received
Frame
Transmitted
Frame