When deploying the Campus Infrastructure module, adopting best
practice recommendations at the access layer means providing a highly available
and deterministic Layer 2 network. It is generally assumed that High
Availability in the Access layer will be accomplished through the
implementation of link redundancy between access and distribution layers with
the STP protocol managing the use of those links. Redundant links to individual
user devices is not typical.
These are best practices to follow when
establishing highly available access Layer devices.
- Limit VLANs to a single access switch or switch stack. Spanning VLANs
across switches may be necessary in some instances but should be avoided if at
all possible.
- Leave the Spanning Tree Protocol active if there are no redundant Layer 2
links in the network. This will guard against the attachment of rogue switches.
- Rapid spanning tree is preferred to keep convergence times to 1-2
seconds.
- Setting trunks permanently on, to avoid auto-negotiation and security
issues.
- If two different version of Cisco software exist at either end of a trunk
link ensure that trunk parameters and manually set to match on another.
- VTP can be disabled or run in transparent mode only
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NOTE:
Consider using multilayer switches and routing at the access layer to
avoid the use of spanning tree and minimize convergence time.
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