3

I have a computer1 connected to ip phone which is connected to an HP J9625A switch like this:

switch <-> ip_phone <-> computer1

l have been continuously receiving snmp traps close to 10000 traps with the following traps on computer2:

port 4 is now off-line

port 4 is Blocked By STP

I noticed in the snmp trap event screen that there were no "port 4 is now on-line" entry. Testing the connection from the switch port 4 to the ip phone with a cable tester indicates that a problem exists with the connection. Yet I do not understand why STP would block this port.

3
  • If you somehow have a loop, then STP will recognize that, and it should block the port.
    – Ron Maupin
    Oct 11 '16 at 15:39
  • Ports are blocked until they switch to the forwarding state. This is normal behavior.
    – Ron Trunk
    Oct 11 '16 at 16:41
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 15 '17 at 4:24
4

These are normal log messages for a port bouncing on a HP Procurve/Aruba switch. The normal sequence of events for a port (connected to a non-STP edge host as most IP phones are) coming on-line and then off-line is:

  1. Port is Blocked by STP
  2. Port is now on-line
  3. Port is now off-line

The port enters STP blocked when it is first brought up. There is a 3 second delay before the port can be brought on-line. This is due to the auto-edge feature, which waits 3 seconds and if it doesn't receive any STP BPDUs, it decides the port is an STP edge port and brings it on-line without waiting for the normal STP timers. When the port goes down, we see the off-line message. In your case I guess the port isn't staying up for 3 seconds, so you only see messages 1 & 3.

If you want, you can set the port to admin-edge-port, which may bring it on-line without the 3 second delay, but this isn't really going to help due to the cabling fault. You need to troubleshoot the cabling fault. The messages are normal and don't indicate any STP issues.

1

There are two possibilities:

A) Because the cable tester indicates a problem, the port is flapping all the time causing the switch so send traps en masse. Have a look at the port's uptime.

B) By definition an edge port has no other bridges attached to it. But the phone has a switch built in and therefore counts as a bridge. There may be a software feature that is triggered whenever more than one MAC address is learned on the edge port.

1
  • If you want to look up the definition of an edge port: IEEE 802.1Q-2014 on page 434 or IEEE 802.1D-2004 on page 151. Oct 11 '16 at 18:07

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