Error map
DNS lookups take 5 seconds (timeout then retry) Networking: Every connection pauses about 5 seconds — resolv.conf nameserver timeout, then fallback to the next DNS server
Networking · layer 2, Network
Centre: this error. First ring: errors it is linked with (10). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (10)
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
DNS not working inside a Kubernetes pod (could not resolve host / nslookup: can't resolve)
Pods can’t resolve service names or external hosts — CoreDNS is down, blocked by NetworkPolicy, or the upstream resolver fails.
Networking: ping — Request timed out / 100% packet loss (host drops or filters ICMP)
No echo reply arrived in time: the host is down, unreachable, or simply ignores ping.
Networking: Sites load slowly or hang for seconds — broken IPv6 (AAAA resolves, IPv6 route missing) falling back to IPv4
The client prefers IPv6, but the IPv6 path is broken, so every connection waits for a timeout before using IPv4.
Networking: nc -vz hangs then times out — firewall silently DROPs packets (REJECT would answer "Connection refused")
A connection attempt gets no answer at all, which points to a firewall dropping the packets rather than a closed port.
Networking: kernel: nf_conntrack: table full, dropping packet — new connections fail on a Linux firewall/NAT host
The connection-tracking table is full, so the kernel drops packets for any new connection.
Networking: dig: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL — resolver failed to answer (DNSSEC validation or upstream failure)
The DNS resolver couldn't get a valid answer, often because DNSSEC signatures are broken or the authoritative servers fail.
Networking: VPN connected but internal names like db.corp.local don't resolve — split DNS / 127.0.0.53 stub resolver not using the VPN DNS
The VPN works by IP, but internal hostnames fail because queries still go to your normal DNS server.
Networking: DNS changed but the domain still resolves to the old IP — TTL and resolver caching ("propagation")
You updated a DNS record, but resolvers and devices keep serving the old answer until its TTL expires.
Networking: dig: status: REFUSED / recursion requested but not available — the DNS server won't resolve queries for you
The DNS server answered, but its policy refuses to look up names for your address.
Two steps away (30)
Error: getaddrinfo ENOTFOUND host / Name or service not known
DNS lookup for the hostname failed — the name is wrong, doesn’t exist, or this machine can’t resolve it.
fatal: unable to access 'https://github.com/…': Could not resolve host: github.com
DNS lookup for the Git host failed from this machine.
java.net.UnknownHostException: api.example.com
DNS resolution failed for the hostname.
net::ERR_NAME_NOT_RESOLVED (This site can't be reached — server IP address could not be found)
DNS couldn’t resolve the hostname in the browser.
cURL error 6: Could not resolve host: api.example.com
PHP cURL couldn’t resolve the hostname via DNS.
ACM certificate stuck in Pending validation
ACM is waiting to see the DNS (or email) validation record — it wasn’t created, was created in the wrong DNS zone, or has a typo.
Cloudflare Error 1020: Access Denied
A Cloudflare firewall/WAF custom rule blocked the request — the visitor’s IP, country, user agent or request pattern matched a bl…
driver failed programming external connectivity on endpoint: iptables: No chain/target/match by that name
Docker’s iptables rules were wiped (firewalld/ufw reload, iptables flush) while Docker was running, so it can’t publish ports.
ssh: connect to host x port 22: Connection timed out
SSH packets get no reply — a firewall/security group drops them, the server is off, or the IP is wrong.
connect: Network is unreachable (ENETUNREACH)
The host has no route to the destination network — no default gateway, interface down, or trying IPv6 without IPv6 connectivity.
ERR_CONNECTION_TIMED_OUT: This site can’t be reached — example.com took too long to respond
The browser waited for the server but got no response — the server is down/unreachable, a firewall drops traffic, or DNS points t…
Chrome: This site can’t be reached — The webpage at https://… might be temporarily down. ERR_ADDRESS_UNREACHABLE
The computer has no route to the server’s IP address — often an IPv6 problem, a wrong local-network address, or a VPN routing iss…
connect: No route to host (EHOSTUNREACH)
The destination host isn’t reachable — it’s down, on another subnet without routing, or a firewall rejects with “host unreachable…
Azure SQL: Cannot open server 'x' requested by the login. Client with IP address 'y' is not allowed to access the server (Error 40615)
The Azure SQL server firewall doesn’t allow your client’s IP address.
SMTP: telnet smtp.example.com 25 — Connection timed out (cloud provider blocks port 25)
Connections from your server to other mail servers on port 25 time out because your cloud host or ISP blocks outbound SMTP to fig…
Networking: `arp -n` shows (incomplete) / Destination Host Unreachable — no ARP reply from the next hop
The machine asked "who has this IP?" and nobody on the local network answered.
Networking: connect: Cannot assign requested address — ephemeral port range exhausted by TIME_WAIT connections
The machine ran out of local ports for new outgoing connections to the same destination.
Networking: NAT gateway ErrorPortAllocation / SNAT port exhaustion — intermittent outbound connection timeouts
Many instances share few public IPs, and the NAT gateway runs out of source ports for outbound connections.
dial tcp: lookup registry-1.docker.io: no such host / Temporary failure in name resolution during docker build
DNS isn’t working for the Docker daemon or inside build containers, so pulls and package downloads fail.
sudo: unable to resolve host <hostname>: Name or service not known
The machine’s hostname isn’t in /etc/hosts (or DNS), so sudo prints this warning — usually after changing the hostname.
Cloudflare Error 523: Origin is unreachable
Cloudflare can’t find a network route to your origin server — the DNS record points to a wrong/unroutable IP or the origin networ…
Networking: Server reachable from the internet but not from inside the LAN via its public IP — NAT loopback / hairpin NAT not working
Devices on your own network can't use the router's public address to reach a server that is also on that network.
Networking: VPN is connected but I can't reach the internal network — missing routes, split tunnel or overlapping subnets
The tunnel is up, but traffic for the office/VPC subnets isn't sent through it or comes back the wrong way.
Networking: Handshake for peer did not complete after 5 seconds, retrying (try 2) — WireGuard tunnel never establishes
The WireGuard peers can't complete the cryptographic handshake, so no traffic flows.
Cloudflare HTTP 530 (with Error 1016 Origin DNS error / 1033 tunnel error)
Cloudflare returns 530 together with a 1xxx error; the 1xxx code (usually 1016 or 1033) tells you the real cause.
Cloudflare Error 1000: DNS points to prohibited IP
A proxied DNS record points at a Cloudflare IP address, creating a loop.
Cloudflare Error 1001: DNS resolution error
Cloudflare received the request but the hostname isn’t set up on Cloudflare (or the domain was just added and not active yet).
Cloudflare Error 1002: DNS points to Prohibited IP / Restricted
A record points to a private, reserved or Cloudflare IP that Cloudflare won’t proxy to.
Cloudflare Error 1003: Direct IP access not allowed
The request went to a Cloudflare IP address directly (or with a Host header for a domain not on Cloudflare).
Cloudflare Error 1004: Host Not Configured to Serve Web Traffic
The DNS record was just created or changed and Cloudflare hasn’t propagated it yet — or Spectrum/non-HTTP ports are involved.
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