Error map
VPN connected but internal subnets unreachable Networking: VPN is connected but I can't reach the internal network — missing routes, split tunnel or overlapping subnets
Networking · layer 2, Network
Centre: this error. First ring: errors it is linked with (7). 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 (7)
Networking: Two hosts on one LAN can't talk — subnet mask or network address mismatch
The hosts disagree about which addresses are local, so one tries to route traffic that should go straight across the LAN.
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.
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: ping — Destination Host Unreachable / Destination net unreachable (ICMP type 3)
A router (or your own PC) tells you it has no way to deliver the packet to that address.
Networking: %OSPF-5-ADJCHG: Nbr 10.0.0.2 from EXSTART to DOWN — OSPF neighbor stuck in EXSTART/EXCHANGE (MTU mismatch)
Two OSPF routers see each other but never finish exchanging databases, cycling between EXSTART and DOWN.
Networking: IKE: received NO_PROPOSAL_CHOSEN — IPsec peers can't agree on encryption, hash or DH group
The two VPN gateways offered encryption settings that have nothing in common, so the tunnel never comes up.
Networking: SSH/HTTPS connects but hangs on large data — path MTU discovery black hole
Small packets pass but full-size ones vanish, so logins work and then transfers or page loads stall.
Two steps away (20)
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.
Networking: Windows has detected an IP address conflict / Duplicate address detected by 00:aa:bb:cc:dd:ee
Two devices on the same network are using the same IP address, so traffic reaches the wrong one or neither.
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: wlan0: WPA: 4-way handshake failed - pre-shared key may be incorrect / WRONG_KEY
The Wi-Fi association started but key negotiation failed, almost always a wrong password.
Networking: ping: local error: message too long, mtu=1500 / Packet needs to be fragmented but DF set
A packet is larger than the path MTU and is marked "don't fragment", so a router discards it.
Networking: netstat -su: packet receive errors, receive buffer errors — UDP datagrams dropped by a full socket buffer
UDP packets arrive faster than the application reads them, so the kernel throws the extras away.
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
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: 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.
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 405 Method Not Allowed
The URL exists, but it doesn’t accept the HTTP method you used (e.g. POST to a GET-only route).
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…
Cloudflare Error 1019: Compute server error (Workers)
A Cloudflare Worker routed the request to a loop or hit an internal compute error.
SMTP: 554 5.4.14 Hop count exceeded - possible mail loop
The message passed through too many mail servers (usually over 25), which almost always means two systems forward mail to each ot…
Networking: %CDP-4-NATIVE_VLAN_MISMATCH / device on the wrong VLAN can't reach the gateway
A port or trunk carries a different VLAN than expected, so hosts silently land on the wrong network.
OpenSSL: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure (SSL alert number 40)
The server aborted the handshake with alert 40 — no acceptable parameters (cipher, signature algorithm, client certificate or SNI…
Networking: Your Remote Desktop Services session has ended. Possibly the network connection was lost / Remote Desktop disconnected, error code 0x904
An established Remote Desktop session dropped because the network under it stalled or the session was reset.
Networking: netstat -s: segments retransmitted / Wireshark: TCP Retransmission, TCP Dup ACK — packet loss on the path
Packets are being lost, so TCP resends them and throughput collapses.
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: TCP: request_sock_TCP: Possible SYN flooding on port 80. Sending cookies. Check SNMP counters.
The server's pending-connection queue filled, so the kernel switched to SYN cookies to survive.
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