DRAG DROP
Drag the network characteristic on the left to appropriate Access-Distribution block design on the right.
Answer: 
Explanation:
Layer 2 loop-free design: In this design, the access switches use Layer 2 switching.
The links between the access and distribution layers are configured as Layer 2 trunks.
The link between the distribution switches is configured as a Layer 3 routed link. An
EtherChannel is typically used for this link to increase availability. In this design, there are no
Layer 2 loops in the access-distribution block, which means that the Spanning Tree Protocol is not
involved in network convergence and load balancing.
All the ports are in the spanning-tree Forwarding state. Load balancing of the traffic from the
access to the distribution layer is based on the First Hop Router Protocol (FHRP) that is used in
this design. Reconvergence time in the case of failure is driven primarily by FHRP reconvergence.
A limitation of this solution is that it is optimal for networks where each access layer VLAN can be
constrained to a single access switch.
Stretching VLANs across multiple access switches is not recommended in this design.
Layer 2 looped design: The Layer 2 looped design also uses Layer 2 switching on the access
layer, and the links between the access and distribution switches are also configured as Layer 2
trunks. However, unlike the Layer 2 loop-free design, the link between the distribution switches is
configured here as a Layer 2 trunk. This configuration introduces a Layer 2 loop between the
distribution switches and the access switches. To eliminate this loop from the topology, the
Spanning Tree Protocol blocks one of the uplinks from the access switch to the distribution
switches. This design is recommended for networks that require an extension of VLANs across
multiple access switches. A drawback is that network convergence in the case of failure is now
dependent on spanning-tree convergence that is combined with FHRP convergence. Another
downside is limited load balancing. PVST root election tuning can be used to balance traffic on a
VLAN-by-VLAN basis. However, within each VLAN, spanning tree always blocks one of the
access switch uplinks.Layer 3 routed design: The Layer 3 routed design uses Layer 3 routing on the access switches.
All links between switches are configured as Layer 3 routed links. The advantage of this design is
that it eliminates the Spanning Tree Protocol from the interswitch links. It is still enabled on edge
ports to protect against user-induced loops, but it does not play a role in the network
reconvergence in the access-distribution block. FHRPs are also eliminated from the design,
because the default gateway for the end hosts now resides on the access switch instead of on the
distribution switch.
Network reconvergence behavior is determined solely by the routing protocol being used. Like the
Layer 2 loop-free design, the Layer 3 routed design constrains VLANs to a single access switch.
Also, this design does not allow VLANs to be extended across multiple access switches, and it
requires more sophisticated hardware for the access switches.
Because the Spanning Tree Protocol recogni7cs the EtherChannel link as a single logical link,
spanning tree is effectively removed from the network topology. Like the layer 2 loop-free design,
spanning tree is still enabled to guard against loops that are caused by miswiring or other human
errors. It no longer plays a role in network convergence, how-ever. A primary advantage of designs
that are based on the MEC is that all links between the access and distribution layers are used in
forwarding. Traffic is load balanced across the links through the EtherChannel hashing
mechanisms.
Another advantage is that this design allows VLANs to extend across multiple access switches if
necessary, without introducing Layer 2 loops into the topology.
