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Examples

p4net ships eight runnable example topologies under examples/ in the repository. Each one isolates a single capability so the source is easy to read and copy. Run any of them with:

sudo p4net examples/<name>/topology.py

(or sudo python examples/<name>/topology.py if you don't have the console script on PATH).

What's bundled

  • Quick start (port swap) — two hosts on a single switch with a hardcoded port-swap pipeline. The smallest working topology; no runtime table programming needed.
  • L3 forwarding — same two hosts, but the pipeline routes via an ipv4_lpm table that's programmed from Python at startup. ARP is pre-seeded.
  • CPU punt — a one-host topology where every dataplane packet is punted to the controller via the CPU port. Demonstrates <switch> packet send and <switch> packet listen.
  • Dual stack — two hosts each with both IPv4 and IPv6 addresses on the same /24 and /64. Shows the per-interface IPv6 sysctl gating.
  • Asymmetric link — two hosts with per-direction link delay. Demonstrates delay_a_to_b / delay_b_to_a and the resulting one-way RTT asymmetry.
  • IPv6 LPM — two IPv6-only hosts with a 128-bit LPM table programmed at runtime. Shows how <switch> table dump renders IPv6 entries in human form (fd00::1/128) instead of raw bytes.
  • INT (in-band telemetry) — single-switch INT: the pipeline inserts a 14-byte shim header carrying switch identity, ingress timestamp, egress port, queue depth, and the original etherType. A raw-socket listener decodes the shim on the receiver.
  • Multi-hop INT — two switches in series each insert their own shim; the listener decodes the full hop-by-hop stack. Production-style telemetry topology; same P4 binary on both switches, identity supplied by the v1.2 register API.

How they fit together

Example Hosts Switches IPv4 IPv6 Asymmetric CPU punt Runtime tables Telemetry
quick_start 2 1 ✓
l3_forwarding 2 1 ✓ ✓
cpu_punt 1 1 ✓ ✓
dual_stack 2 1 ✓ ✓
asymmetric_link 2 1 ✓ ✓
ipv6_lpm 2 1 ✓ ✓
int 2 1 ✓ ✓ ✓
int_multi_hop 2 2 ✓ ✓ ✓ (×2)

The Tutorial combines every feature in one 4-host, 2-switch program — useful as a kitchen-sink example, but each individual feature is easier to understand in isolation here.