TCP port reachability past firewall troubleshooting
TCP-SYN traceroute survives ICMP filtering; nc -zv confirms open port
traceroute -T -p 443 <host>; nc -zv <host> 443
more troubleshooting
all 32 commands →
Bypass DNS with curl --resolve
curl -sv --resolve <host>:443:<ip> https://<host>/healthz
In-cluster DNS smoke test
kubectl run dnsutils --image=tutum/dnsutils -it --rm --restart=Never -- nslookup kubernetes.default
Query CoreDNS directly
dig +short @$(kubectl -n kube-system get svc kube-dns -o jsonpath='{.spec.clusterIP}') <name>.<ns>.svc.cluster.local
Inspect CoreDNS config and logs
kubectl -n kube-system get cm coredns -o yaml; kubectl -n kube-system logs deploy/coredns --tail=50
TLS cipher and protocol enum
nmap --script ssl-enum-ciphers -p 443 <host>