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September 15 2011

Ali Abbas » Linux Kernel Route Cache

To understand the importance of the routing cache, it is important to keep in mind and visualize the 3 main routing hash tables in use in the kernel for routing decisions… the Route Cache (what we will be discussing), the Route Policy Database and the Route Table. It is also in this order that the network subsystem queries the tables to make a forwarding decision. To display the “Route Cache”, one could simply issue the “ip route show cache” command.

September 14 2011

intrace - intrace - Traceroute-like application piggybacking on existing TCP connections - Google Project Hosting

InTrace is a traceroute-like application that enables users to enumerate IP hops exploiting existing TCP connections, both initiated from local network (local system) or from remote hosts. It could be useful for network reconnaissance and firewall bypassing.
Sponsored post
Reposted bySchrammelhammelMrCoffeinmybetterworldkonikonikonikonikoniambassadorofdumbgroeschtlNaitliszpikkumyygittimmoejeschge

September 09 2011

Network lab with User Mode Linux | Vincent Bernat

All those tools are a great way to setup your network lab. Look at them! If you want to setup a virtual network lab for educational purpose, one of those should fit your purpose. However, none of those solution were a perfect match for me. I did not want to maintain some root filesystem. I wanted my lab to start in a few seconds. I wanted to keep all configuration files (including the ones for the virtual hosts) into one subdirectory of my home and be able to modify them while the lab was running. I also wanted to be able to plug some Cisco router using Dynamips/Dynagen.

None of the listed solution above matched all those criteria. Therefore, I setup my own lab script with User Mode Linux. This is not a complete solution, but is more like a home-made solution to match one particular need. You cannot use the final result without tweaking it. Again, look at the other solutions first.

Network lab: site to site VPN | Vincent Bernat

The goal of this lab is to setup a site-to-site IPsec VPN. This lab is similar to my first lab using UML. The major differences are:

We only setup one VPN instead of two.
Static routing is used in place of BGP for inter-site routing. Moreover, BIRD is used as a routing daemon.
VPN are using an external network for Internet access.
Both internal network and external network are redundant using one OSPF instance each.

August 29 2011

July 20 2011

How to kill a TCP connection using netstat

You cannot kill a TCP connection using netstat utility. netstat is use for

Display network connections
Routing tables
Interface statistics
Masquerade connections
Multicast memberships
And much more

However Linux support two other commands or utility that can be used to kill a TCP connection.

June 20 2011

May 26 2011

April 13 2011

Keeping Topology Drawings Clean - Packet Life

People often try to cram too much information onto a network topology drawing, which results in cluttered diagrams that are difficult to follow. While it is commendable to want to convey every detail of a network's architecture, these details can be arranged in two categories: things that go on a topology drawing, and things that go on a spreadsheet. The difference between the two can be determined by keeping in mind the purpose of a topology drawing, which is simply to convey how packets flow across a network. Details which aren't needed to support this function belong on a spreadsheet or in some similar database.

April 11 2011

streams - Play with pcap files

streams is a tool for browsing, mining and processing TCP streams in pcap files. It provides a command line prompt for filtering, selecting and dumping reassembled session data. It can further invoke external tools to pipe stream data through.

January 12 2011

Emulating WANs with WANem - Packet Life

I recently noticed someone on Twitter asking for software to emulate WAN connections for lab purposes. WAN emulation introduces artificial delay, bandwidth restrictions, and other impediments for the purpose of benchmarking applications and protocols against real-world conditions. I suggested WANem, having read a bit about it, but realizing that up that point I had never actually used it. What a great topic for a blog article!

November 24 2010

Fallback gateways

Fallback-gw is a little Perl script to be called via cron
that (1) checks availibility of neighbor routers using ping
and (2) activates backup routing on ping failure.

It can be used as a stupid replacement for BGP/OSPF in a multihomed environment.

November 04 2010

CTAN: directory: /tex-archive/macros/latex/contrib/bytefield

The bytefield package helps the user create illustrations for network protocol specifications and anything else that utilizes fields of data. These illustrations show how the bits and bytes are laid out in a packet or in memory.

October 28 2010

September 30 2010

.:: Phrack Magazine ::. Fun with the Spanning Tree Protocol

An idea of 1st group of attacks lies practically ``on the surface''. Essentially the principle of STP allows easily organize Denial of Service (DoS) attack. Really, as defined by standard, on Spanning Tree reconfiguration all ports of involved devices does not transfer user frames. Thus, to drop a network (or at least one of its segments) into unusable state it's enough to master STP-capable device(s) to do infinite reconfiguration. It could be realized by initiating elections of, for example, root bridge, designated bridge or root port - practically any of electional object. ``Fortunately'' STP has no any authentication allowing malicious users easily reach this by sending fake BPDU.

September 12 2010

GNS3 | Graphical Network Simulator

GNS3 is a graphical network simulator that allows simulation of complex networks.

To allow complete simulations, GNS3 is strongly linked with :

* Dynamips, the core program that allows Cisco IOS emulation.
* Dynagen, a text-based front-end for Dynamips.
* Qemu, a generic and open source machine emulator and virtualizer.

GNS3 is an excellent complementary tool to real labs for network engineers, administrators and people wanting to pass certifications such as CCNA, CCNP, CCIP, CCIE, JNCIA, JNCIS, JNCIE.

It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers.

This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X.
Reposted bysicksinopalodefuego

Welcome to GNS3 Vault


Cool Scenarios to get the maximum out of your networking experience ;)

Downloadable topologies that you can use right away with the GNS3 software.

Different levels of difficulty, there's something for everyone...novice, intermediate and expert!

The forum where you can discuss about all the labs.

It's possible to review labs.

You can share your labs with others.
Reposted bysicksin sicksin

Juniper Clue

Have Juniper routers? Have clue or need clue? If so, this site is for you.

Juniper Clue seeks to provide a compendium of useful knowledge, from the field, about Juniper products. This site is neither affiliated with nor endorsed by Juniper Networks. All users are encouraged to contribute by making edits to pages, see Help:Editing for more information.

September 09 2010

Introducing tcprstat, a TCP response time tool | MySQL Performance Blog

In a nutshell, it is a lightweight way to measure response times on a server such as a database, memcached, Apache, and so on. You can use this information for historical metrics, capacity planning, troubleshooting, and monitoring to name just a few.

The tcprstat tool itself is a means of gathering raw statistics, which are suitable for storing and manipulating with other programs and scripts. By default, tcprstat works just like vmstat: it runs once, prints out a line, and exits. You’ll probably want to tell it to run forever, and continue to print out more lines. Each line contains a timestamp and information about the response time of the requests within that time period. Here “response time” means, for a given TCP connection, the time elapsed from the last inbound packet until the first outbound packet. For many simple protocols such as HTTP and MySQL, this is the moral equivalent of a query’s response time.

September 02 2010


Some of you have noticed that I've started using new icons in my topology drawings lately. I recently discovered a wealth of impressive Visio shapes provided for free by the good folks at VSD Grafx, who do custom Visio shape development. They offer three identical sets of 110 generic network shapes (one set each in blue, green, and grey) of impressive quality. Here are just a handful.


These shapes are 100% vector images, meaning that they scale perfectly to any degree.

Free Visio Icons from VSD Grafx - Packet Life
Reposted bydatenwolffpletz
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