ip phone power

[kevinzike]

Cisco IP phone will not power up on an active data line?

How to troubleshoot?

[William Bell]

1. Ensure that you are plugging into a switch that supports power over ethernet.

2. Ensure that the PoE standard supported by the switch is also supported by the phone. Basically, you need to ensure that if you are using Cisco pre-standard PoE that the phone supports this. On the other hand, if your phone supports IEEE 802.3af (or at) then make sure your switch supports the appropriate standard.  IOW, make sure they are compatible.

3. Ensure that the interface is configured appopriately. Compare it to a known good. On Cisco IOS: show runn

4. Check the interface to see if it is in err-disabled mode. On Cisco IOS: show interface status

5. Ensure that there is adequate power available to power the network port. For some Cisco switches you will not be able to provide power to all ports. Depends on what you bought, if you added the appropriate power supply, etc. On Cisco IOS: show power inline

HTH.

Regards,
Bill

[Will Pettit]

what model of phone and switch is it?

As above, some of the newer phones require a different PoE type. E.G. a 7937 phone won't work on a 3550 switch but will on a 3750 switch.

[Ven Taylor]

The simplest way to check is to go to the switch and type "show power inline".

If the port you're connecting the phone to is providing power, it will tell you.

Some of the earlier model switches don't provide PoE on EVERY port.  If you don't have enough remaining power, new phones won't power up.

Prior to our IP phone rollout, we had to replace all of our older model switches for this very reason.

Here's an excerpt from one of my switches:

Switch>show power inline
Available:370.0(w)  Used:117.0(w)  Remaining:253.0(w)

Interface Admin  Oper       Power   Device              Class Max
                            (Watts)                           
--------- ------ ---------- ------- ------------------- ----- ----
Gi0/1     auto   off        0.0     n/a                 n/a   15.4
Gi0/2     auto   off        0.0     n/a                 n/a   15.4
Gi0/3     auto   off        0.0     n/a                 n/a   15.4
Gi0/4     auto   off        0.0     n/a                 n/a   15.4
Gi0/5     auto   on         6.3     IP Phone 7942       2     15.4
Gi0/6     auto   off        0.0     n/a                 n/a   15.4
Gi0/7     auto   on         6.3     IP Phone 7942       2     15.4
Gi0/8     auto   off        0.0     n/a                 n/a   15.4
Gi0/9     auto   off        0.0     n/a                 n/a   15.4
Gi0/10    auto   off        0.0     n/a                 n/a   15.4
Gi0/11    auto   off        0.0     n/a                 n/a   15.4
Gi0/12    auto   on         12.0    IP Phone 7965       3     15.4
Gi0/13    auto   off        0.0     n/a                 n/a   15.4
Gi0/14    auto   off        0.0     n/a                 n/a   15.4
Gi0/15    auto   off        0.0     n/a                 n/a   15.4
Gi0/16    auto   off        0.0     n/a                 n/a   15.4
Gi0/17    auto   off        0.0     n/a                 n/a   15.4
Gi0/18    auto   off        0.0     n/a                 n/a   15.4
Gi0/19    auto   on         15.4    Ieee PD             0     15.4
Gi0/20    auto   on         15.4    Ieee PD             0     15.4
Gi0/21    auto   on         15.4    Ieee PD             0     15.4
Gi0/22    auto   on         15.4    Ieee PD             0     15.4
Gi0/23    auto   on         15.4    Ieee PD             0     15.4
Gi0/24    auto   on         15.4    Ieee PD             0     15.4

Hope this helps!

Ven Taylor