Socket summary stats troubleshooting
One-shot socket totals by state; SYN-SENT pileup hints at SYN drops/firewall
ss -s; ss -tan state syn-sent | wc -l
more troubleshooting
all 32 commands →
Path MTU discovery
tracepath -n <host>; ping -M do -s 1472 -c2 <host>
Confirm egress route and ARP
ip route get <ip>; ip neigh show | grep -E 'FAILED|INCOMPLETE'
TCP port reachability past firewall
traceroute -T -p 443 <host>; nc -zv <host> 443
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