Category Archives: Computer

Extend snmpd to add detailed CPU statistics, per cpu

I needed to export detailed CPU statistics from Linux servers using SNMP. While UCD-SNMP-MIB export some detailed stats, it only does it for the whole system. I may have missed something easier though :-) So here is a BASH script, … Continue reading

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Unetlab: create a QEMU image

So you have your Unified Networking Lab (UNL) server running and you want to use arbitrary QEMU images with it. Here is how to create one. All UNL data is stored under /opt/unetlab , images are stored under /opt/unetlab/addons and … Continue reading

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Cisco IOS PPTP server : PPP: Packet throttled, Dropping packet

If you get the following message on your Cisco router when you connect a VPN client using PPTP *Mar 17 16:43:02.371: Vi5 PPP: Control packet rate limit 10 reached *Mar 17 16:43:02.371: Vi5 PPP: Entering block state for 30 seconds … Continue reading

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Microsoft Windows 7 PPTP issues: spurious ICMP protocol-unreachable sent

I was recently confronted to a strange issue with a PPTP VPN connection to a central site. Some users could connect and some others could not. They all used Windows 7 with SP1, configured the same way, and all computers … Continue reading

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Ubuntu 14.04 and USB to Serial ch341 (chinese device from Ebay)

You can find pretty cheap USB to Serial devices on Ebay. I bought one and received a device using a chip ch341. Unfortunately, the drive is bugged in Ubuntu 12.04 and 14.04. Fortunately, there is patch to fix it. Here … Continue reading

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Update GNS3 server on GNS3 IOU VM

GNS3 Sourceforge account provides an OVA image ready to run gns3-server for those who want to use Cisco IOS on Unix images . However, at the time of this writing, the gns3-server version is outdated (1.3.3). The client must have … Continue reading

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Migrate Debian 6+ to another server with minimal downtime

Recently I had to migrate services from a running Debian server to another one, with minimal downtime of services. I usually do this to P2V or V2V Linux systems, as this allows me to resize the new virtual machine to … Continue reading

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SNOM phones and presence monitoring

If you have issues with your SNOM phones and presence monitoring (the little LEDs that display when another extension is ringing or busy), then maybe this will help. We had this problem at work. When we checked the SIP traces, … Continue reading

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Nagios and LSI RAID cards

To monitor the status of a LSI RAID card, say for example a Dell PERC card, you will need to install NRPE, sudo, mpt-status and check_mpt.sh . Install sudo and NRPE via your package manager. You can grab mpt-status via … Continue reading

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VMware and Windows poor TCP performance

I have had a strange issue lately with Windows servers on VMware vSphere 5.1 hosts. Throughput of TCP connections between some virtual machines were very very slow, barely 10 mbit/s . The behavior was easily reproducible : just start an … Continue reading

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