Chapter 3: System planning
Data network planning
Page
3-42
This is the Translation Bridging feature, which you can enable in the General page of the Configuration web
page in the AP. When this feature is disabled, the setting of the Send Untranslated ARP parameter has no
effect, because all packets are forwarded untranslated (with the source MAC address intact). See
on Page
Engineering VLANs
The radios support VLAN functionality as defined in the 802.1Q (Virtual LANs) specification, except for
the following aspects of that specification:
•
Protocols:
o
Generic Attribute Registration Protocol (GARP) GARV
o
Spanning Tree Protocol (STP)
o
Multiple Spanning Tree Protocol (MSTP)
o
GARP Multicast Registration Protocol (GMRP)
•
Embedded source routing (ERIF) in the 802.1Q header
•
Multicast pruning
•
Flooding unknown unicast frames in the downlink
As an additional exception, the AP/BHM does not flood downward the unknown unicast frames to the
SM/BHS.
A VLAN configuration in Layer 2 establishes a logical group within the network. Each computer in the
VLAN, regardless of initial or eventual physical location, has access to the same data. For the network
operator, this provides flexibility in network segmentation, simpler management, and enhanced security.
Special case VLAN numbers
This system handles special case VLAN numbers according to IEEE specifications:
Table 88 Special case VLAN IDs
VLAN Number
Purpose
Usage Constraint
0
These packets have 802.1p priority, but are
otherwise handled as untagged.
Must not be used as a
management VLAN.
1
Although not noted as special case by IEEE
specifications, these packets identify traffic that
was untagged upon ingress into the SM and
must remain untagged upon egress. This policy
is hard-coded in the AP.
Must not be used for
system VLAN traffic.
4095
This VLAN is reserved for internal use.
Must not be used at all.
SM membership in VLANs
With the supported VLAN functionality, the radios determine bridge forwarding on the basis of not only
the destination MAC address, but also the VLAN ID of the destination. This provides flexibility in how
SMs are used:
