Online Insertion & Removal
OIR is a feature of the 6500 allowing hot swapping most line cards without first powering down the chassis. The advantage of this is that one may perform an in-service upgrade. However, before attempting this, it is important to understand the process of OIR and how it may still require a reload.
To prevent bus errors, the chassis has three pins in each slot which correspond with the line card. Upon insertion, the longest of these makes first contact and stalls the bus (to avoid corruption). As the line card is pushed in further, the middle pin makes the data connection. Finally, the shortest pin removes the bus stall and allows the chassis to continue operation.
However, if any part of this operation is skipped, errors will occur (resulting in a stalled bus and ultimately a chassis reload). Common problems include:
- Line cards being inserted incorrectly (and thus making contact with only the stall and data pins and thus not releasing the bus)
- Line cards being inserted too quickly (and thus the stall removal signal is not received)
- Line cards being inserted too slowly (and thus the bus is stalled for too long and forces a reload).
Read more about this topic: Catalyst 6500
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