tag:blogger.com,1999:blog-3423420718518803005Mon, 09 Sep 2024 21:39:13 +0000LinuxNetworkingCiscoGeneralLoadbalancingdebianCentOSsshwiresharkclientdesktopdnsgnomeinstalljessieBGPEXFreeDesktop.orgHP-UXIS-ISJuniperJuniper ethernetJunosconsoleconversationsddnseditcapemailencryptionerroresxievolutionexchangef5 pluginfreeBSDgzrecovergzrtinodeskdekeepalivemacosmenuoffice365ospfpcapqnapsearchsearch-domainsearchdomainserialtcppreptcpreplaytcprewritetoolstunnelvim-cmdvirtualizationwheezyYAIJ - Yet another IT journalhttp://yy27.blogspot.com/noreply@blogger.com (Valentin)Blogger30125tag:blogger.com,1999:blog-3423420718518803005.post-5658993758642774749Wed, 26 Jul 2017 09:55:00 +00002017-07-26T12:53:17.442+02:00f5 pluginwiresharkThe documentation I could find on F5 devcentral about installing the f5 wireshark plugin goes about compiling wireshark from sources, patching the code to include the f5 plugin, etc. After downloading the 2.2.0 version I could see that the plugin is already in binary format, namely f5ethtrailer.so (this goes for all platforms, except windows where this is a dll file). To install the plugin in http://yy27.blogspot.com/2017/07/install-f5-f5ethtrailerso-wireshark.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-5748665156305134470Tue, 18 Jul 2017 23:44:00 +00002017-07-19T01:51:30.838+02:00errorEXfreeBSDinodesJuniperJunosGot into an issue a couple of days ago on a Junos EX virtual chassis where the following was being reporded > show system snapshot media internal member 0 fpc0: -------------------------------------------------------------------------- error: Could not create temporary directory The command tries to create a temporary directory into the /tmp filesystem and it fails. Going to the shell prompt http://yy27.blogspot.com/2017/07/juniper-ex-error-could-not-create.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-6902301838189392621Wed, 14 Jun 2017 09:22:00 +00002023-09-29T09:34:04.642+02:00dnsGeneralmacossearch-domainsearchdomainI recently started using a Mac laptop (with MacOS Sierra) for work and one thing soon saw was that the search-domains were not appended when trying to use utilities such as ping or ssh (tough the configuration in the network preferences lists domain.com in the list of search-domains). So, saying I have host1.domain.com using the following: ping host1 would not resolve host1 (no search-domain http://yy27.blogspot.com/2017/06/macos-append-search-domain.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-3685451414647879651Mon, 16 Jan 2017 12:57:00 +00002017-06-14T11:23:28.786+02:00ddnsdnsGeneralLinuxqnapI was looking recently to allow remote access into my home QNAP NAS from remote locations. My IP address at home is dynamic so I needed a DDNS provider and some port forwarding on the home router. My setup at home is simple. My internet connection is over a DSL line. I have a DSL router from the ISP serving as an Wifi access point for my devices at home. It also has 4 ethernet ports and to one ofhttp://yy27.blogspot.com/2017/01/ddns-and-qnap.htmlnoreply@blogger.com (Valentin)4tag:blogger.com,1999:blog-3423420718518803005.post-8881515963155335592Sun, 08 Jan 2017 19:51:00 +00002017-01-08T22:22:46.548+01:00IS-ISNetworkingGeneral: - routing protocol for ISO CLNP (Connectionless Network Protocol) - NET (Network Entity Title) required by configuration (L3 address) Has different formats. One practical is below:    Area (1-13 bytes)| System ID (6 bytes) | Selector (1 byte) (eg. 47.000|1921.6810.0001|00)    Selector is 00 in a NET. The NET must begin with one octet (eg 47) and end with one octed (http://yy27.blogspot.com/2017/01/general-routing-protocol-for-iso-clnp.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-204458963994991255Tue, 03 Jan 2017 22:47:00 +00002017-01-03T23:47:23.631+01:00BGPNetworkingNeighbor states: Idle: all connections are refused Connect: wait for TCP to establish Active: initiates the TCP connections OpenSent: Local waits for Open message from peer. After receiving open, if no errors BGP sends keepalive OpenConfirm: BGP waits for keepalive or notification Established: Can exchange update, notification and keepalive Message types: Open: sent when TCP 3way is complete. http://yy27.blogspot.com/2017/01/bgp-notes.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-7582787694251865746Tue, 03 Jan 2017 16:10:00 +00002017-01-03T23:49:05.459+01:00NetworkingospfPacket types: Hello (type1): used to discover neighbors, build and maintain adjacencies DBD(type2): database description packets. These are a summary of the topological database. Detects MTU mismatches (fragmentation is not allowed). Have bits I (start of DBD), M (more ackets DB), MS(master/slave used to decides who starts sending DBD first) LSR(type3): link state request. Request specific link http://yy27.blogspot.com/2017/01/ospf-notes.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-5088100233971606566Wed, 14 Dec 2016 13:09:00 +00002016-12-15T14:02:00.840+01:00debiandesktopLinuxsearchI have just tried Catfish for local files search. I am using it (at time of writing version 1.2.2) with Debian Jessie  and Xfce desktop. Every time I opened catfish I was prompted to update the database as it was never updated. I was updating this with administrative rights, but after closing and opening the application the same message was displayed. From the message prompthttp://yy27.blogspot.com/2016/12/catfish-fails-to-update-database-in.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-3826122661186439683Fri, 11 Dec 2015 16:24:00 +00002015-12-11T17:30:10.637+01:00esxiLinuxsshvim-cmdvirtualizationOne of the ways to manage ESXi virtual machines is through vim-cmd commands. You can look at a quick tutorial of the command here. Let's say there are a multitude of ESXi servers in your environment and you'd like to manage some virtual machines through cli. One way to do this is to run vim-cmd commands over ssh. For example, I have 2 ESXis named in the example esxi1 and esxi2. On both of them Ihttp://yy27.blogspot.com/2015/12/cli-remote-management-of-esxi-virtual.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-7877509838846573288Thu, 13 Aug 2015 10:05:00 +00002015-12-10T16:34:17.924+01:00editcapJuniper ethernetpcapwireshark When capturing packets on a Junos device, the output packet capture will include a Juniper ethernet header. Example of such capture: tcpdump -c1 -nvvr capture.pcap reading from file JTAC.pcap, link-type JUNIPER_ETHER (Juniper Ethernet) 14:58:06.569634  Juniper PCAP Flags [Ext], PCAP Extension(s) total length 16    Device Media Type Extension TLV #3, length 1, value Ethernet http://yy27.blogspot.com/2015/08/how-to-remove-juniper-ethernet.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-903007266561309081Thu, 14 May 2015 13:48:00 +00002015-12-10T16:39:05.668+01:00gzrecovergzrtLinuxtools A tool to recover gzip corrupted compressed files is gzrecover. This comes with in the recovery toolkit package gzrt. $gzip -d compressed_file.gz gzip: compressed_file.gz: unexpected end of file $file compressed_file.gz compressed_file.gz: gzip compressed data, from Unix $gzrecover compressed_file.gz $ls compressed_file* compressed_file.gz compressed_file.recovered http://yy27.blogspot.com/2015/05/recovering-corrupted-gzip-files-gzip.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-4012764929809482401Tue, 12 May 2015 14:03:00 +00002015-12-10T17:19:35.199+01:00clientdebianencryptionLinuxNetworkingsshtunnel SSH tunnels allow you to forward a local TCP port to a remote machine and vice versa. The tunnel option is available in many ssh clients. I will give the example here on how to create SSH tunnels with putty and the openssh-client. I will consider in the below that we want to access the SERVER on port 80 (http server). Scenario 1. SSH tunnel setup with local port forwarding. The http://yy27.blogspot.com/2015/05/ssh-tunnels-set-up-and-port-forwarding.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-7489154983391870170Thu, 07 May 2015 13:15:00 +00002015-12-10T17:23:33.766+01:00desktopFreeDesktop.orggnomeinstalljessiekdeLinuxmenu Users can create shortcuts for an application to appear in menus, desktop,  etc. by creating a .desktop file. This desktop file contains a listings of configuration for the application. In order for your desktop environment to "see" this file, this .desktop file will have to be placed either in /usr/share/applications - for system wide applications - or in ~/.local/share/applications - if http://yy27.blogspot.com/2015/05/linux-add-menu-and-desktop-entry-for.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-2778710014109456434Fri, 01 May 2015 11:59:00 +00002015-12-10T17:32:02.687+01:00clientdebianemailevolutionexchangegnomejessieLinuxoffice365 Evolution is a personal information management application that provides integrated mail, calendaring and address book functionality. To connect to office365 exchange you will need the evolution program and the evolution-ews plugin. Installation: % sudo apt-get install evolution evolution-ews Account setup: 1. Obtain the information about your domain's office365 servers. To find http://yy27.blogspot.com/2015/05/connect-evolution-email-client-to.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-7941632984548306269Wed, 11 Feb 2015 21:24:00 +00002015-12-10T17:39:13.484+01:00consoledebianinstallLinuxserialwheezy I wanted to install Debian wheezy on a machine without a video card and no CDROM. I had a 1GB USB and I tried initially the easy way, as described in https://www.debian.org/releases/stable/amd64/ch04s03.html.en#usb-copy-isohybrid by just copying the cd image to my /dev/sda (USB stick) but I did not got any output on the console. I copied the iso file to another linux machine, mounted it as a http://yy27.blogspot.com/2015/02/installing-debian-wheezy-from-usb-over.htmlnoreply@blogger.com (Valentin)1tag:blogger.com,1999:blog-3423420718518803005.post-1825996534869466738Tue, 03 Feb 2015 18:39:00 +00002015-02-03T19:39:13.062+01:00conversationsNetworkingwireshark Among other very useful and interesting things that wireshark can show in a packet capture, it can also display the top traffic conversations based on various criteria such as IP addresses, L2 ethernet addresses, IPv6 address or L4 information. The conversation list is available from the Statistics -> Conversations menu. Below an example taken showing the top bps rate (B->A http://yy27.blogspot.com/2015/02/how-to-identify-top-traffic-speakers.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-5113988452531988006Mon, 02 Feb 2015 15:34:00 +00002015-12-10T17:54:05.288+01:00CentOSkeepaliveLinuxssh The SSH connection can be kept alive either with SSH keepalive packets (encrypted) or with TCP keepalive packets. This allows also to detect hanging sessions and disconnect the hanging client/server when a connection has become inactive. On a open SSH server, to control the SSH keepalive packets the parameters are: ClientAliveCountMax 3 (default) ClientAliveInterval 0 (default) - means the SSH http://yy27.blogspot.com/2015/02/open-ssh-keepalive.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-8766689685001433553Thu, 29 Jan 2015 08:57:00 +00002015-12-11T12:25:31.555+01:00LinuxNetworkingtcppreptcpreplaytcprewrite Tcpreplay is a suite of tools that allows editing and replaying previously captured traffic in libpcap format. This can come handy in many situations, one common use is traffic pattern based behavior re-creation in a lab environment. Tcpreplay suite comes with the following tools: tcpprep - multi-pass pcap file pre-processor which determines packets as client or server and creates cache http://yy27.blogspot.com/2015/01/replaying-packets-with-tcpreplay.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-8004796910516161718Wed, 22 Jul 2009 15:27:00 +00002015-12-11T14:21:40.129+01:00CiscoLoadbalancingNetworkingThe scope of this post is to show how to delete archived files on a Cisco CSS11501. In order to delete other files (core dumps, logs, etc) the procedure is similar, you just need to know what you want to delete. In order to manipulate the files we need to go to debug mode: CSS11501# llama Then the ap_file command provides the "File commands using Complete pathnames". To delete the http://yy27.blogspot.com/2009/07/how-to-delete-files-from-css11501.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-5155514605582756995Sat, 30 May 2009 00:33:00 +00002015-12-11T15:14:49.402+01:00CentOSGeneralLinux mdadm is a tool for managing, creating and reporting on Linux software RAID arrays. I will describe some tips which I found useful at the moment. Improve RAID1 re-sync time with write-intent bitmap The RAID driver writes out periodically bitmap information recording which areas of the RAID component have been modified since the RAID array was last in sync. If, for example one of two members ofhttp://yy27.blogspot.com/2009/05/mdadm-tips-on-linux-software-raid.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-9088490872251062762Mon, 04 May 2009 15:17:00 +00002015-12-11T15:19:10.326+01:00CiscoLoadbalancingNetworking Few days ago I had to reconfigure a running CSS 11501 loadbalancer from an existing configuration in which traffic initiated from some services running in one VLAN towards any destination was source NAT-ed to a selective NAT which was based on the destination IP address. What I wanted to do is almost exactly to what is described in this official Cisco document with the difference that I had morehttp://yy27.blogspot.com/2009/05/css11500-source-groups-and-acl.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-7804423228612111307Mon, 16 Mar 2009 13:30:00 +00002015-12-11T15:25:48.689+01:00CiscoLoadbalancingNetworking In the picture illustrated in which two Cisco CSS 11501 Loadbalancers were providing a redundant setup with fate sharing, the route from the "Servers" networks towards the client network was provided through an IP setup on a redundant interface shared by the 2 Loadbalancers. The VRRP announcements for the virtual routers holding redundant interfaces on vlans A,B between the two loadbalancers http://yy27.blogspot.com/2009/03/vrrp-mastermaster-issue-on-css-11501.htmlnoreply@blogger.com (Valentin)2tag:blogger.com,1999:blog-3423420718518803005.post-8777273492690920699Sun, 22 Feb 2009 16:05:00 +00002015-12-11T15:30:26.575+01:00HP-UX For HP-UX (click here for latest release) you can tune the UDP local ephemeral port range separately from the TCP local ephemeral port range. In a previous post it was shown how to alter/view the ephemeral port range for a Linux system. To follow up the example from my Linux post in order to set on HP-UX the local port range from 15000 till 61000 we can use the ndd utility for the change on http://yy27.blogspot.com/2009/02/hp-ux-ephemeral-port-range-for-tcpudp.htmlnoreply@blogger.com (Valentin)0tag:blogger.com,1999:blog-3423420718518803005.post-8924451560649413942Thu, 05 Feb 2009 23:08:00 +00002015-12-11T15:32:32.883+01:00GeneralLinux The range of ephemeral ports a client program can use (unless otherwise specified by the program) on modern Linux OS distributions by default is from 32768 till 61000 (for systems with more than 128 MB RAM) and from 1024 till 4999 (or even less) for systems with less than 128MB of RAM. This range is defined in the kernel parameter /proc/sys/net/ipv4/ip_local_port_range and it affects both TCP ashttp://yy27.blogspot.com/2009/02/linux-ephemeral-port-range-for-tcpudp.htmlnoreply@blogger.com (Valentin)1tag:blogger.com,1999:blog-3423420718518803005.post-2447821491853446048Tue, 03 Feb 2009 11:21:00 +00002015-02-02T20:59:47.764+01:00CiscoLoadbalancingNetworking By default the Cisco CSS 11501 series loadbalancers will create an implicit internal service to check the availability of the gateways for its static defined routes. This internal service monitors the availability of the route which goes through a specific gateway by sending ICMP keepalives to that gateway. In that way if the internal service is in "Alive" state, the route for which the internalhttp://yy27.blogspot.com/2009/02/cisco-css-11500-series-internal.htmlnoreply@blogger.com (Valentin)0