As a network admin, one of your important tasks is to stay on top of the availability and performance of different devices within your network, so you can plan and make the necessary changes or fixes to ensure the smooth functioning of your network as a whole. SNMP is a protocol that greatly eases this […]
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Lets Dive into what an SNMP Trap is and a Small Guide into SNMP and its Components – Find out what they Do and How they Help you Monitor Servers!
What is Netflow ? Lets jump into the Definition, Exporters, Collectors & Analyzers – Lets Learn About What it is! Learn How to Monitor & Manage It!
Simple Network Management Protocol, or SNMP in short, is a protocol used to manage different devices on an IP network. This protocol is mostly used to collect information about managed devices on IP networks and to use that information to change the behavior of these devices. It is also used to identify devices, monitor the […]
Here’s the Best Network Troubleshooting Tools & Software for Diagnosing Network Issues, connectivity problems and much more all for FREE!
Here’s our favorite Network Traffic Generators for Stress Testing Tools and Software for LAN & WAN Bandwidth Generation.
Here’s the Top Alternatives to Traceroute for Network Connectivity Troubleshooting, Hop-by-Hop Analysis and Bandwidth Analysis
Here is a text version of /etc/services that might be useful for determining whether a port is being used by a trojan, etc: TCP and UDP Service Listing
There is some apparent voodoo on what, exactly, is needed to add an IP address to an interface using Red Hat style scripts. We have tested this on Red Hat Enterprise 3 and CentOS 4, and it appears that the convention is quite forgiving. This makes sense, really, since if you hose up these interfaces, […]
If you wish to bring up a Cisco router that has an IP address that conflicts with existing hosts on your network, there are a variety of ways to change it. We just happened to have a crossover network cable sitting on our work bench, and a GNU/Linux host on the LAN with an extra […]
Nmap can be used to fingerprint operating systems. Here is a typical session: [root@srv-1 usr-1]# nmap -O –min_rtt_timeout=6000 10.50.100.1-80 Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2006-05-05 12:49 PDT Interesting ports on 10.50.100.1: (The 1656 ports scanned but not shown below are in state: closed) PORT STATE SERVICE 22/tcp open ssh 111/tcp open rpcbind 6000/tcp […]
Here is a diagram of three servers: What we want to do is create a tunnel with SSH so that 10.50.101.100 can go directly to 10.50.100.72. There is no routing between the networks. The box in between is dual-homed and acting as a security buffer between the 10.50.100 and 10.50.101 networks. After we set up […]
There is a limit on the number of concurrent socket connections that an application can accept in BSD, Windows, and other operating systems. This is set at compile time, but it can be overridden. Here is a discussion of this limitation by Microsoft, and here is further discussion. One application that is sticking this on […]
Here is our subnet reference guide and The Perl script used to generate it If you want an easy to use subnetting calculator, Subnet-Calculator.org is one of the best ones we’ve seen online. Subnet Reference Guide — Value of individual bits in an eight bit byte if true: Bit 7 = 128 Bit 6 = […]
If you have a WAN, then one very important concern should be latency. Latency, in this case, is the time that a package of information takes to reach the other end of the slow link. This package of information could be a DNS query, ping, file, or a transaction in a client/server application. Notice that […]
There are some nasty, nasty SNMP vulnerabilities that have recently been revealed. Many different products are affected. See the CERT Advisory Here. This inspired us to upgrade our Cisco. To upgrade the IOS on your Cisco router, you have a couple of options. You can either upgrade via TFTP, or you can use the console. […]
We picked up a Watchguard Firebox FB-10R from RE-PC (Tukwila) for 15 bucks. There is almost always some kind of auction on Ebay selling a Firebox FB-10. The motherboard on ours, it turns out, was damaged. Now the Firebox FB-10R is just a regular PC clone. It has three 3COM 3C509 NICs in it. We […]
In this story we showed how to upgrade IOS on a Cisco using a TFTP server available from Cisco that ran on Windows. Well, just suppose you wanted to load a new IOS image from a TFTP server on a GNU/Linux box. We will use Red Hat 8.0 to provide a TFTP server. First, install […]