Add iperf3 traffic generator for DC<->Campus gold VRF path

Host containers sit idle otherwise, leaving IPFabric ARP/MAC tables and
Grafana throughput graphs empty until someone manually generates traffic.

Refs #55

scripts/README.md

@@ -133,3 +133,33 @@ default layout.
   data for any VTEP node — likely an Arista internal-vs-front-panel VLAN
   translation gap. Only affects that one decorative tooltip metric, not
   node/link status or traffic coloring. Tracked in #44.
+
+# scripts/generate_traffic.sh
+
+Generates real DC↔Campus traffic over VRF `gold` using `iperf3` (bundled
+in the `network-multitool` image every host container runs), with a live
+bandwidth dashboard. Without this, host containers sit idle and IPFabric
+ARP/MAC tables, Grafana throughput graphs, and the weathermap panel stay
+empty until someone manually generates traffic (see #55).
+
+## Quickstart
+
+```bash
+./scripts/generate_traffic.sh <duration_seconds>
+```
+
+## How it works
+
+- Starts `iperf3 -s` on the DC gold-VRF servers: `dc-server2`
+  (10.34.34.102), `dc-server4` (10.78.78.104).
+- Runs `iperf3 -c` from the paired campus gold-VRF hosts: `campus-host1`
+  → dc-server2, `campus-host2` → dc-server4 — exercising the full
+  DC→Core→Campus stitched EVPN Type-5 path end to end.
+- Redraws a terminal dashboard every second for the run duration: server
+  list, and live Mbits/sec per client session parsed from `iperf3 -i 1`
+  output.
+- On exit (duration end or Ctrl-C), kills the client processes and stops
+  the `iperf3 -s` processes on the DC servers — no leftover state.
+
+`dc-server1`/`dc-server3` (VLAN 40, VRF default, no gateway) are out of
+scope — this script only exercises the routed gold VRF path.