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DHCP Sensor - Could not open UDP Port 68. Please make sure this port is not in use. (code: PE091)

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Hello,

i have installed PRTG 12.3.4.2994 on a Windows 7 machine (VM on ESXi Host). Configured a DHCP Sensor on the Probe Device, but the sensor doesn't work. Error: Could not open UDP Port 68. Please make sure this port is not in use. (code: PE091)

But my DHCP server is working correctly in my network and there a enough IP's free.

On both machines (PRTG and DHCP server) the firewall is off. i played with the timeout setting is 10, 20 and 200 seconds, but no luck.

deleted the sensor and added a new with the correct network interface of the PRTG server, no luck.

regards

dhcp pe091 udp-68

Created on Oct 29, 2012 2:55:30 PM by  dvi (-2) 1



14 Replies

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Hello,

the error means that PRTG cannot use the DHCP port on the machine it is running on to send out a DHCP-request. Please check with netstat what other application is blocking the port.

best regards.

Created on Oct 29, 2012 5:58:49 PM by  Torsten Lindner [Paessler Support]



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Hi,

on the PRTG server no entry found for Port UDP 68. On the DHCP server UDP 68 is showing his own server IP.

On the PRTG server I have 2 network interface configured as packet sniffer interfaces.

is this a problem? netstat showes me not a entry for the udp 68 port on these both NIC's

only these:

UDP 169.254.80.159:137 *:*

UDP 169.254.80.159:138 *:*

UDP 169.254.80.159:1900 *:*

UDP 169.254.80.159:56373 *:*

UDP 169.254.213.199:137 *:*

UDP 169.254.213.199:138 *:*

UDP 169.254.213.199:1900 *:*

UDP 169.254.213.199:56372 *:*

regards

Created on Oct 30, 2012 11:13:19 AM by  dvi (-2) 1



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Does restarting the PRTG Probe Service help then?

Created on Oct 30, 2012 12:10:28 PM by  Torsten Lindner [Paessler Support]



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Not really, after restarting the Probe Service i have now the error: No data yet. trying repeatedly "check now" but no luck.

Created on Oct 30, 2012 12:30:37 PM by  dvi (-2) 1



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Now is have the same error message: Error: Could not open UDP Port 68. Please make sure this port is not in use. (code: PE091)

Created on Oct 30, 2012 12:38:57 PM by  dvi (-2) 1



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The error means that PRTG cannot listen on UDP port 68 (on the machine where PRTG is installed), maybe this is blocked by the firewall or similar. In anyway, if PRTG cannot listen on this port, it can't use the DHCP-Sensor. This needs to be possible.

Created on Oct 31, 2012 1:52:45 PM by  Torsten Lindner [Paessler Support]



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The Firewall is off. there is no other security software installed , like a Antivirus or Internet Security Suite. When i check with wireshark and filter the result with (bootp.option.type == 53) i can't see any package no DHCP Discover, Offer, Request, ....

any idea?

Created on Nov 30, 2012 10:56:24 AM by  dvi (-2) 1



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Hi Paessler, we have the same problem here. DHCP Sensors throw the UDP Port error periodically on all our (3) probes. Netstat does not show any service blocking port 68. Any insights on your side?

Regards

Matin Schiemann

Created on May 6, 2014 8:51:11 AM by  kbb (0)



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Hello, which exact version of PRTG are you running? How long does the error on the sensors persist? Does it resolve itself, or do you need to add the sensor(s) anew? Or maybe restart the Probe Service?

Created on May 7, 2014 11:33:34 AM by  Torsten Lindner [Paessler Support]



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Hi Paessler, sorry for the delayed answer. We do still experience this problem periodically on all our 4 probes with DHCP sensors. We are running prtg latest stable. All probes are win 7 with no firewall or other blocking software. netstat shows the connection to our prtg core server only.

The problem occurs about 5-10 times a day on each of our probes. The dhcp sensors check server ip and resultstring. Interval is 5 minutes.

Would you like me to open a support issue? Our license is 1000 sensors.

Kind regards

Matin Schiemann

Created on Jul 12, 2014 4:30:35 AM by  matin (0) 1



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How many DHCP - Sensors do you have per Probe Device?

Created on Jul 14, 2014 9:12:45 AM by  Torsten Lindner [Paessler Support]



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We have one DHCP sensor per probe device.

Created on Aug 26, 2014 4:30:36 AM by  matin (0) 1



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We only have one DHCP sensor per probe device.

Created on Aug 26, 2014 4:41:01 AM by  matin (0) 1



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I'm afraid such sporadic errors are very hard to catch and may not be caught here. Please try working around the issue, with using latencies on potential triggers, that allow for at least another scan after the error.

Created on Aug 27, 2014 3:07:10 PM by  Torsten Lindner [Paessler Support]



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