Free network monitor software for linux

Very Simple Network Monitor is a complete rewrite of project PHP Monitoring.
Its by default capable of monitoring via ping, UDP and TCP checks. Has builtin plugin system so customized scripts can be used to monitor whatever you like eg. oracle tablespaces, diskspace whatever; Alarms are also generated via plugins, it has standard EMAIL alarm, but can be customized to have snmp traps, or sms gateways or whatever.
Can store uptime reports in mysql and generated reports and uptimes in % availability per service.
Has one centralised html monitoring page with all alarms together for good overview.
Enhancements:
- reporting bug fixed
- alarm causes nmonitor to be locked bug fixed
- some other minor stuff I cant remember
- removed some typos from INSTALL doc:)

NAT Monitor is a tool to monitor hosts bandwidth usage in a Linux-NAT network.

A daemon collects data and clients display them (currently a GTK app with graph and a text version). It detects new hosts, saves up to 12 hours of data, and has a nice summary statistic.

Sleek Monitor is a combination of basic monitors for:
- OS
- KDE
- Kernel
- CPU & cache
- GPU & GPU Temp
- Memory
- Wired & Wireless networks
- battery with time
- date and calendar

Network Probe and protocol analyzer is the ultimate tool for traffic-level network monitoring, troubleshooting, analysis,
If your network is crawling to a standstill, and you suspect there might be a problem with the network traffic, Network Probe will quickly help you identify what is causing the problem, show you who is generating any troublesome traffic, and where the traffic is being transmitted.
Network Probe will collect traffic statistics for all protocols, hosts, and conversations on your network, and show you all the top talkers and listeners on your network. Hosts generating large amounts of traffic such as music and movie streaming, playing online games, or listening to streaming media are easily identified.
Main features:
- Watch in real time which protocols are used on your network
- Watch in real time which hosts are active on your network and the Internet
- Watch in real time which conversations are taking place on your network and to and from the Internet
- Watch in real time detailed protocol statistics per host
- Watch in real time detailed protocol statistics per conversation
- Watch in real time network card details for your network
- Watch traffic amount of selected entries relative to the total and filtered traffic
- Watch traffic amount over time for any host, conversation, and protocol
- Watch in real time network throughput for the entire network segment
- Inspect detailed logged statistical data from days and weeks earlier
- Filter out and search for selected protocols, hosts, conversations, and network cards
- Sort network traffic by amount of data transmitted or received
- Export network traffic statistics data
- Configure users with restricted access to statistical data
- Password protected login

Network Time Tools (NTT) is a set of network tools designed to provide monitoring of a network and the services on that network, and provide various reports on the hosts/services and optional alerts via email, pager, and cellphones. It also has the capability to send messages on user-specified services to email, pagers and cell phones.
Main features:
- Bandwidth measurement based on time intervals
- Checks Service availibilty on specified Hosts for the following protocols:
- ftp
- ssh
- telnet
- dns
- http ( specific pages )
- www ( simple head )
- pop
- nntp
- imap
- irc
- smtp
- Ability to send alerts based on user specified services to:
- pagers
- cell phones
- email
- A frontend that displays a daily report that can be viewed by a web browser or cell phone.
- views specific servers
- views specific services
- views bandwidth measurements
- view alerts
- Data stored in a Mysql Database
- Easily configurable via an XML config file
- Runs in Daemon or one-shot mode

Nmonitor is a monitoring tool, by default capable of monitoring via ping, UDP and TCP checks.
It has builtin plugin system so customized scripts can be used to monitor whatever you like eg. oracle tablespaces, diskspace whatever.
This tool was written because I needed a very simple network monitor, and thats what it is, dont expect any miracles from this thing.
Enhancements:
- No extra features, just some bugfixes
- reporting bug fixed
- alarm causes nmonitor to be locked bug fixed
- some other minor stuff I cant remember
- removed some typos from INSTALL doc:)

Simple Monitor is a SuperKaramba theme inspired by the simple but effective "Very Simple Monitors" theme by the user humanthing. Some values are not displayed properly though in Very Simple Monitors (network values and IP). This could be because of different setups. My computer is pretty standard so my theme should function properly on most pcs. http://www.kde-look.org/content/show.php?content=48973
I like a tight and clean desktop, so I simplified the idea even more. This theme is showing all basic information, and nothing more.
Main features:
- Processors type
- Processor speed
- Processor load (number and graph, for one proc)
- Processor Temperature
- Amount of ram used / amount of ram
- amount of swap used / amount of swap
- amound of HDD space used / amount of HDD space total (for "/root" and "/home")
- HDD temperatue (for "/hda", I could add another drive if requested)
- Computer name
- Computer ip
- Network load (up- and download, values and graph)
- Amount of transfered data thrue internet (up- and download) since last boot
Enhancements:
- Made the three blocks clickable.
- The CPU block opens Processor information
- The Memory block opens KsysGuard (youll need to have it installed to be able open it, obviously. Its in Kubuntu by default)
- the Network block opens your computers ip settings window
- Added a line for your computers uptime
- Changed font colors to very dark gray and very light gray, instead of black and white, to make it look softer.