Cisco POE switch port flaps

270 pts.
Tags:
Cisco
IP phones
PoE
Switches
I have a Cisco PoE switch flapping 3 of my 12 ports providing power to connected 3com hubs. The configuration is the same for all switch ports and is set at defaults. debugging poe events outputs the following which seems to indicate the switch is probing for an IP phone.

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I would suggest disabling POE on these ports going to the 3com hubs. This will help with the switch power budget. To disable POE try the following steps:

Step 1
configure terminal – Enter global configuration mode.

Step 2
interface interface-id - Enter interface configuration mode for the physical interface to be configured.

Step 3
power inline {auto | never} -Configure PoE on the interface:
**Enter auto (the default) to set the interface to automatically detect if a connected device requires power and to supply power to the device if enough power is available.
**Enter never to disable power detection and supply for the interface.

Step 4
end – Return to privileged EXEC mode.

Step 5
show power inline [interface-id | module switch-number] – Display PoE status for a switch or switch stack, for the specified interface, or for a specified stack member.

Step 6
copy running-config startup-config – (Optional) Save your entries in the configuration file.

**************************************************

We power the 3com hubs from the switchport so disabling the PoE is not an option. Are you suggesting that the switch does not have power budget to supply power to all 12 ports?

Discuss This Question: 4  Replies

 
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  • Peterp
    For some reason I could not paste the logs when I created the question so here they are. Sep 25 10:37:20.354 EDT: ILP Start PHY Cisco IP phone detection ( Fa0/17 ) Okay Sep 25 10:37:20.390 EDT: ILP State_Machine( Fa0/17 ): State= ILP_LINK_UP_S, Event= PHY_LINK_DOWN_EV Sep 25 10:37:20.390 EDT: ****Power controller address 0x24**** Sep 25 10:37:20.394 EDT: Reg 0x0 = 8 Sep 25 10:37:20.394 EDT: Reg 0x1 = E6 Sep 25 10:37:20.394 EDT: Reg 0x2 = 0 Sep 25 10:37:20.394 EDT: Reg 0x4 = F Sep 25 10:37:20.394 EDT: Reg 0x10 = DD Sep 25 10:37:20.394 EDT: Reg 0x12 = FF Sep 25 10:37:20.398 EDT: Reg 0x13 = 0 Sep 25 10:37:20.398 EDT: Reg 0x14 = D Sep 25 10:37:20.398 EDT: Reg 0x17 = 80 Sep 25 10:37:20.398 EDT: ************************************* Sep 25 10:37:20.398 EDT: ILP uses Link Disconnect( Fa0/17 ): state= ILP_LINK_UP_S, event= PHY_LINK_DOWN_EV Sep 25 10:37:20.398 EDT: ILP Power Off at ( Fa0/17 ) Okay Sep 25 10:37:20.402 EDT: ILP After Power Off at ( Fa0/17 ), port re-config Okay Sep 25 10:37:20.402 EDT: ILP Power Off at ( Fa0/17 ) Okay Sep 25 10:37:20.406 EDT: ILP After Power Off at ( Fa0/17 ), port re-config Okay Sep 25 10:37:20.406 EDT: ILP Power Accounting RELEASE_PWR ( Fa0/17 ) Okay, pwr_used= 165000 Sep 25 10:37:20.746 EDT: ILP State_Machine( Fa0/17 ): State= ILP_DETECTING_S, Event= TWTI_PWR_GOOD_EV Sep 25 10:37:20.750 EDT: ****Power controller address 0x24**** Sep 25 10:37:20.750 EDT: Reg 0x0 = 8 Sep 25 10:37:20.750 EDT: Reg 0x1 = E6 Sep 25 10:37:20.750 EDT: Reg 0x2 = 0 Sep 25 10:37:20.750 EDT: Reg 0x4 = F Sep 25 10:37:20.750 EDT: Reg 0x10 = DD Sep 25 10:37:20.754 EDT: Reg 0x12 = FF Sep 25 10:37:20.754 EDT: Reg 0x13 = 0 Sep 25 10:37:20.754 EDT: Reg 0x14 = D Sep 25 10:37:20.754 EDT: Reg 0x17 = 80 Sep 25 10:37:20.754 EDT: ************************************* Sep 25 10:37:20.754 EDT: ILP uses Link Disconnect( Fa0/17 ): state= ILP_DETECTING_S, event= TWTI_PWR_GOOD_EV Sep 25 10:37:20.754 EDT: ILP Power Accounting REQ_PWR ( Fa0/17 ) Okay Sep 25 10:37:21.354 EDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/17, changed state to down Sep 25 10:37:22.390 EDT: %LINK-3-UPDOWN: Interface FastEthernet0/17, changed state to down Sep 25 10:37:22.790 EDT: ILP State_Machine( Fa0/17 ): State= ILP_PWR_GOOD_USE_LINK_DISC_S, Event= PHY_LINK_UP_EV Sep 25 10:37:22.790 EDT: ****Power controller address 0x24**** Sep 25 10:37:22.790 EDT: Reg 0x0 = 8 Sep 25 10:37:22.790 EDT: Reg 0x1 = E6 Sep 25 10:37:22.790 EDT: Reg 0x2 = 0 Sep 25 10:37:22.794 EDT: Reg 0x4 = F Sep 25 10:37:22.794 EDT: Reg 0x10 = DD Sep 25 10:37:22.794 EDT: Reg 0x12 = FF Sep 25 10:37:22.794 EDT: Reg 0x13 = 0 Sep 25 10:37:22.794 EDT: Reg 0x14 = D Sep 25 10:37:22.794 EDT: Reg 0x17 = 80 Sep 25 10:37:22.794 EDT: ************************************* Sep 25 10:37:22.798 EDT: ILP uses Link Disconnect( Fa0/17 ): state= ILP_PWR_GOOD_USE_LINK_DISC_S, event= PHY_LINK_UP_EV Sep 25 10:37:26.818 EDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/17, changed state to up ****************************************************************************************
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  • Labnuke99
    Yes, it is likely that the Cisco switch does not have enough power for the 3com devices. Is there a reason you are unable to have a power brick for the 3com hubs? The typical Cisco POE port provides 15.4 Watts of power.
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  • Peterp
    we didn't order the 3com hubs with the power brick and they are a temporary solution we have to work with for a few more weeks so I don't think we'll bother to get any. the switch is providing the power to all 12 of my 3coms. See output below. It is just that occasionally the same 3 ports fa0/11,15,17 will drop. We might get one or two drops a day or no drops in a day. so the issue is intermittent. But it only happens to these 3 ports and many times it happens to all 3 at the same time. CSWT24F#sh power inline Interface Admin Oper Power Device (Watts) ---------- ----- ---------- ------- ------------------- Fa0/1 auto on 15.0 unknown Fa0/2 auto off 0 n/a Fa0/3 auto on 15.0 unknown Fa0/4 auto off 0 n/a Fa0/5 auto off 0 n/a Fa0/6 auto off 0 n/a Fa0/7 auto off 0 n/a Fa0/8 auto off 0 n/a Fa0/9 auto off 0 n/a Fa0/10 auto on 15.0 unknown Fa0/11 auto on 15.0 unknown Fa0/12 auto off 0 n/a Fa0/13 auto on 15.0 unknown Fa0/14 auto off 0 n/a Fa0/15 auto on 15.0 unknown Fa0/16 auto off 0 n/a Fa0/17 auto on 15.0 unknown Fa0/18 auto off 0 n/a Fa0/19 auto on 15.0 unknown Interface Admin Oper Power Device (Watts) ---------- ----- ---------- ------- ------------------- Fa0/20 auto on 15.0 unknown Fa0/21 auto on 15.0 unknown Fa0/22 auto on 15.0 unknown Fa0/23 auto off 0 n/a Fa0/24 auto on 15.0 unknown
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  • Labnuke99
    What is on ports 11,15, 17? Are these uplinks to 3 of the hubs? Sounds like maybe the hubs are cycling power or something and taking a surge causing the ports to exceed the power budget.
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