Hierarchical Design 25
The Access Layer
The access layer, shown in Figure 1-11, is the point at which local end users are allowed into
the network. This layer may also use access lists or filters to further optimize the needs of a
particular set of users. The access layer connects a group of LANs and workstations. The access
layer can be compared to a road or street on which houses reside. The access layer allows for
network segmentation based on logical needs, and it isolates broadcast traffic between
workgroups and LANs. User traffic and services should be connected at the access layer.
Figure 1-11
Access Layer
Access router functions include the following:
·
Extended media filtering
·
Segmentation into networks or subnetworks
·
Proxy services
·
Naming services
·
Broadcast forwarding
·
Router discovery and hot standby
·
Connectivity on demand
·
Connection to multicast networks
R1
R3
R2
To distribution
layer
Workgroups
Hub
VLAN A VLAN B
87200333.book Page 25 Wednesday, August 22, 2001 2:18 PM