Describing High Availability in Multilayer Switching
High availability: core layer best practices

These best practices are recommended for optimum core layer convergence.

  • Build triangles, not squares, to take advantage of equal-cost redundant paths for the best deterministic convergence.
  • Design the core layer as a high-speed, Layer 3 switching environment utilizing only hardware-accelerated services. Layer 3 core designs are superior to Layer 2 and other alternatives because they provide:
    • Faster convergence around a link or node failure.
    • Increased scalability because neighbor relationships and meshing are reduced.
    • More efficient bandwidth utilization.
  • When considering high availability in the core, it is assumed that point-to-point links such direct Ethernet links exist between the core and distribution and between core devices. Link up or down topology changes can be propagated almost immediately. With topologies that rely on indirect notification and timer-based detection such as SONET, convergence is non-deterministic and convergence is measured in seconds

Lab Activity

e-Lab Activity: Improving Availability in Multilayer Switched Networks

In this lab, the student will configure HSRP, observe its behavior and troubleshoot if necessary.