iftop

Spec sheet

Purpose

iftop displays current bandwidth usage by pairs of hosts on a network interface.Read 4 Oct 2026 · sources.debian.org

Maker

The manual names Paul Warren as the author.Read 4 Oct 2026 · sources.debian.org

Configuration

iftop can read settings from a configuration file, defaulting to ~/.iftoprc when no alternate file is specified.Read 4 Oct 2026 · sources.debian.org

Filtering

It supports packet filter code and display filters, with display filters affecting what is shown rather than what is captured.Read 4 Oct 2026 · sources.debian.org

Integration

The manual lists tcpdump, pcap, and driftnet as related tools; it does not state integrations with external services.Read 4 Oct 2026 · sources.debian.org

Network support

Configuration options include an IPv4 network boundary and display of link-local IPv6 traffic.Read 4 Oct 2026 · sources.debian.org

Notable limitation

After changing the capture filter, existing display entries may remain for up to 40 seconds because the display reflects a recent capture window.Read 4 Oct 2026 · sources.debian.org

Permissions

iftop must be run with sufficient permissions to monitor all network traffic on the interface.Read 4 Oct 2026 · sources.debian.org

Promiscuous mode

iftop can put the interface into promiscuous mode to capture traffic between other hosts on the same network segment.Read 4 Oct 2026 · sources.debian.org

Security and license

The manual identifies iftop as free software under the GNU General Public License, version 2 or any later version, and provides it without warranty.Read 4 Oct 2026 · sources.debian.org

Terminal output

A text interface without ncurses is available, with options to print a single output after a specified number of seconds and limit the number of lines.Read 4 Oct 2026 · sources.debian.org

Traffic capture

iftop listens on a named interface or, if none is specified, the first interface it finds that looks like an external interface.Read 4 Oct 2026 · sources.debian.org

Traffic views

The display can show host names, port numbers, bandwidth bars, totals, and traffic rates averaged over 2, 10, and 40 seconds.Read 4 Oct 2026 · sources.debian.org

Plans and prices

Every iftop plan and price →

Where Specifiction places it

• Bandwidth Monitoring Software#21 of 337.6