vale(4) a very fast Virtual Local Ethernet using the netmap API


device netmap


is a feature of the netmap(4) module that implements multiple Virtual switches that can be used to interconnect netmap clients, including traffic sources and sinks, packet forwarders, userspace firewalls, and so on.

is implemented completely in software, and is extremely fast. On a modern machine it can move almost 20 Million packets per second (Mpps) per core with small frames, and about 70 Gbit/s with 1500 byte frames.


dynamically creates switches and ports as clients connect to it using the netmap(4) API.

ports are named vale[bdg:][port] where vale is the prefix indicating a VALE switch rather than a standard interface, bdg indicates a specific switch (the colon is a separator), and port indicates a port within the switch. Bridge and port names are arbitrary strings, the only constraint being that the full name must fit within 16 characters.

See netmap(4) for details on the API.


currently supports up to 4 switches, 16 ports per switch, with 1024 buffers per port. These hard limits will be changed to sysctl variables in future releases.


uses the following sysctl variables to control operation:

The maximum number of packets processed internally in each iteration. Defaults to 1024, use lower values to trade latency with throughput.

Set to non-zero values to enable in-kernel diagnostics.


Create one switch, with a traffic generator connected to one port, and a netmap-enabled tcpdump instance on another port:
tcpdump -ni vale-a:1 &
pkt-gen  -i vale-a:0 -f tx &

Create two switches, each connected to two qemu machines on different ports.

qemu -net nic -net netmap,ifname=vale-1:a ... &
qemu -net nic -net netmap,ifname=vale-1:b ... &
qemu -net nic -net netmap,ifname=vale-2:c ... &
qemu -net nic -net netmap,ifname=vale-2:d ... &


An -nosplit The switch was designed and implemented in 2012 by An Luigi Rizzo and An Giuseppe Lettieri at the Universita` di Pisa.

was funded by the European Commission within FP7 Projects CHANGE (257422) and OPENLAB (287581).