Let say we have three EX 4200 switches: SW1, SW2,SW3, we want to use " Dynamic Installation method" to configure them in a chasis mode.
We cable VCP ports in daaisy chained ring toplogy. We set up SW1 and SW2 priority as 255, while SW3 has a default priority of 128.
We power SW1 first then SW2 and finally SW3. They assume following roles:
SW2--Back up RE
Let say we power down SW1, Sw2 assume master and SW3 BACK UP RE role now, next we power on SW1. What role SW1 ,SW2 and SW3 assume ?
MASTER ELECTION CRITERIA:
The algorithm proceeds from the top condition downward until the stated condition is satisfied:
This is my hunch based on the above:
When SW1 powers up and join the Chasis, SW3 will assume LINE CARD ROLE because it has the lowest priority of 128.
SW1 and SW2 have the same priority of 255 so 2nd criteria is used i.e who has the more time in the chasis, since SW1 just joins Chasis therefore SW2 remains Master and SW1 assumes BACK UP RE role.
Am I correct?
Thanks and have a nice weekend!!
Yes, but as I stated previously a small amount of one-time config work to pre-provision the VC, will save you from guessing. Turning on GRES, NSB, NSR who cares is some SW preempts to re-takeover Master, network will run as if nothing changed. With pre-provision (again I think best practice recommendation) you'll always know which SW are RE's and which are line cards.
Dynamic protects better against double-fault of both RE SW's, but likelihood of this happen is VERY remote.