Если сеть traefik-public является attachable

docker run --rm --network traefik-public curlimages/curl -s -o /dev/null -w '%{http_code}\n' -H 'X-Forwarded-For: 1.2.3.4' http://crowdsec_bouncer:8080/api/v1/forwardAuth

docker service create --name curltest --network traefik-public --restart-condition none \
    alpine/curl sh -c "curl -s -o /dev/null -w '%{http_code}\n' -H 'X-Forwarded-For: 1.2.3.4' http://crowdsec_bouncer:8080/api/v1/forwardAuth"
#Ctrl+C
docker service logs curltest
docker service rm curltest