Eaps design

In your opinion, how many nodes can I use in single domain, about 20 still will be ok? I knoiw that in theory eaps doesn't have limnitations.


3 replies

Userlevel 6
Pawel, EAPS does not impose a limitation in the number of nodes in a ring, but there are two factors that you should bear in mind:

  1. EAPS, being a ring topology, will survive to ONE failure. If a second failure occurs, you will lose connectivity. The larger the number of nodes (and links), the higher the probability of having two or more failures.
  2. When a failure is detected (or cleared) the Master switch will send a "Flush-FDB" message through the control vlan. When a Transit node receives this message it flushes its MAC table to relearn the new topology, and retransmits the message to the next switch in the ring. If you have a lot of switches in the ring, the time it takes for the ring to re-converge (that is, the time it takes for all the switches to flush their FDB and re-learn the topology) grows.
For me, the first factor is the most important, but the second should be considered if you need really fast convergence times.
Userlevel 6
We try to keep ours to ten or less for reason number one... Our core which is 12 switches is the exception because several of the nodes are a pair of 8900's setting side by side... At 80 to 90 k mac tables with about 2500 active tag ids on 25 or 30 EAPS rings in the core we still get sub 150ms fail over... flaps hurt though
Userlevel 5
Hi Pawel,
Here is one interesting discussing about EAPS design.

Best regards,