bypass4netns.md

---

title: Accelerating rootless networking with bypass4netns
linkTitle: bypass4netns
weight: 2

---

bypass4netns is an experimental accelerator for rootless networking.

On macOS hosts, it is highly recommended to use the vzNAT networking in conjunction to reduce the overhead of Lima's user-mode networking:

limactl start --network vzNAT

To enable bypass4netns, the daemon process (bypass4netnsd) has to be installed in the VM as follows:

lima containerd-rootless-setuptool.sh install-bypass4netnsd

Then run a container with an annotation nerdctl/bypass4netns=true:

# 192.168.64.1 is the IP address of the "bridge100" interface on the macOS host
lima nerdctl run --annotation nerdctl/bypass4netns=true alpine \
  sh -euc 'apk add iperf3 && iperf3 -c 192.168.64.1'

Benchmark result:

Mode	Throughput
Rootless without bypass4netns	2.30 Gbits/sec
Rootless with bypass4netns	86.0 Gbits/sec
Rootful	90.3 Gbits/sec

Benchmarking environment

• Lima version: 2.0.0-alpha.2

  • nerdctl 2.1.6

  • containerd 2.1.4

  • bypass4netns 0.4.2

• Container: Alpine Linux 3.22.2

  • iperf 3.19.1-r0 (apk)

• Guest: Ubuntu 25.04

• Host: macOS 26.0.1

  • iperf 3.19.1 (Homebrew)

• Hardware: MacBook Pro 2024 (M4 Max, 128 GiB)