traefik-k8s failed to create loadbalancer on ps6

https://github.com/canonical/charm-integration-testing/actions/runs/14159827785/job/39663776657#step:13:788

Sun, 30 Mar 2025 21:04:00 GMT App Version Status Scale Charm Channel Rev Address Exposed Message
Sun, 30 Mar 2025 21:04:00 GMT alertmanager-k8s 0.27.0 active 1 alertmanager-k8s latest/stable 154 10.152.183.178 no
Sun, 30 Mar 2025 21:04:00 GMT loki-k8s 2.9.6 blocked 1 loki-k8s latest/stable 186 10.152.183.184 no Failed to verify alert rules via http://loki-k8s-0.loki-k8s-endpoints.model-25-03-30-20-48-29.svc.cluster.local:3100/...
Sun, 30 Mar 2025 21:04:00 GMT neighbor 0.40.4 waiting 1 grafana-agent-k8s latest/stable 110 10.152.183.69 no Waiting for TLS certificate.
Sun, 30 Mar 2025 21:04:00 GMT prometheus-k8s 2.52.0 active 1 prometheus-k8s latest/stable 232 10.152.183.61 no
Sun, 30 Mar 2025 21:04:00 GMT target active 1 oathkeeper latest/edge 98 10.152.183.52 no
Sun, 30 Mar 2025 21:04:00 GMT traefik-k8s 2.11.0 blocked 1 traefik-k8s latest/stable 232 10.152.183.47 no Traefik load balancer is unable to obtain an IP or hostname from the cluster.
Sun, 30 Mar 2025 21:04:00 GMT vault-k8s active 1 vault-k8s 1.16/stable 323 10.152.183.87 no

From model-25-03-30-20-48-29/service/describe-traefik-k8s-lb.txt
Warning SyncLoadBalancerFailed 3m37s (x8 over 13m) service-controller Error syncing load balancer: failed to ensure load balancer: error creating LB floatingip: Resource not found: [POST https://neutron.ps6.canonical.com:9696/v2.0/floatingips], error message: {"NeutronError": {"type": "ExternalGatewayForFloatingIPNotFound", "message": "External network 55a01b10-91eb-411e-95c2-24d25f1709ce is not reachable from subnet 0acd8fe0-4e85-4ce0-af8e-c9934f4714bf. Therefore, cannot associate Port deb06841-6d3e-4553-bd10-187a47105602 with a Floating IP.", "detail": ""}}: {"NeutronError": {"type": "ExternalGatewayForFloatingIPNotFound", "message": "External network 55a01b10-91eb-411e-95c2-24d25f1709ce is not reachable from subnet 0acd8fe0-4e85-4ce0-af8e-c9934f4714bf. Therefore, cannot associate Port deb06841-6d3e-4553-bd10-187a47105602 with a Floating IP.", "detail": ""}}

Start with the linked GitHub Actions job and the reported model-25-03-30-20-48-29/service/describe-traefik-k8s-lb.txt output. Trace why the traefik-k8s integration deployment cannot obtain a load-balancer address, then validate the fix by rerunning the affected integration test and confirming the service becomes usable.

Written by the indexing model from the issue text.