Catalyst 3750 and RPS 675 behavior

[timwaitepcle]

I have a LAN which incorporates three 3750-24TS-E and two 3750G-24TS-E switches, each connected to its own dedicated RPS 675.

If AC power is lost to the switches they failover to the RPS, as expected. The RPSs and the switches properly indicate (via their respective front panels) that they're running on RPS-supplied DC.

My problem is in restoring AC to the switches and resetting each RPS to indicate that its respective switch is using AC power.

I can reset the non-G switches and RPSs by taking the RPS offline and then bringing it back online; both the RPS's and switch's lights indicate AC power and no reboot is performed.

On the G switches, however, I cannot reset the indicators WITHOUT a reboot. I bring the G switch's RPS offline and when I bring it back online the respective switch reboots.

Why the different behavior between switches within the same family? It's not a crippling issue, but since these switches handle critical traffic, it is very inconvenient.

Is there another way to reset the switches to resotre AC power and reset the respective panel indicator lights without a switch reboot?

Lastly, I cannot find in the switch logs anything which indicates when a switch has failed-over to the RPS. I can get an SNMP notification, but there is nothing in the logs (or at least I can't find it and I willingly admit to being somewhat of a Cisco neophyte). Is there some way to turn that logging on so that power failures are logged?

Thanks in advance,

-Tim

[alagrawa]

Hi Tim,

Thanks for writing in.

Unfortunately we're hitting a hw limitation. What you are experiencing is expected behavior with the RPS300 and RPS675. PS switchover causes 3550/3750 to reboot. This is covered in bug CSCdx81023 and is applicable to RPS 675 also.

I am copying and pasting the release notes from the bug

[Symptom]

Some switches will reboot in the following senario :

1. An RPS300 backs up a switch which loses its internal power supply.

2. The switch's power supply is then restored ( AC is restored, etc.).

3. The RPS300 still continues to back up the switch with the restored AC because they both have switching power supplies and the RPS300 dominates.

4. Then, the RPS300 is backed off by pressing the mode button.

5. Some switches will reboot and some will not reboot. It all depends on how quickly the switch's

internal power supply ramps up to take over. Some will not ramp up quickly enough and the +12V

internal voltage will dip momentarily below +10V, which causes a reboot.

[Work around]

There are no fixes since it is not possible to redesign all the old legacy swtiches supported by the

RPS300. The only solution would have been to have switch internal DC-to-DC converters that functioned at +9V or less.

This issue can occur with non-G switches also. Hence there is no way to switch the PS from the rps to the switch PS without ensuring that the switch will not reboot. UPS may be the answer.

Could not find information regarding the logs for PS fail over events.

Hope this helps.

regards

-Alok