All tools · 🌐 Network Tools
📡 ICMP Type / Code Reference
When debugging a connectivity issue, the ICMP message is often the clue. This reference covers every common ICMP type and code for IPv4 (ICMPv4) and IPv6 (ICMPv6), with one-line meanings.
Loading tool…
Examples
Most common
Output
Type 0 (echo reply) · Type 8 (echo request) · Type 3 (destination unreachable) · Type 11 (time exceeded — TTL 0)Frequently asked questions
Why does PMTU discovery need ICMP?
When a packet is too large, the router drops it and sends ICMP type 3 code 4 ("Fragmentation needed"). If a firewall blocks ICMP, this signal is lost — and large packets silently fail.
About this calculator
ICMP Type / Code Reference runs entirely in your browser using standard formulas. No data is sent to any server. We don't share your inputs with lenders, brokers, or anyone else — there's no funnel and no follow-up email.
Related tools
- 📦 MTU / MSS Calculator — Compute MSS from MTU, account for IPsec/PPPoE/VLAN tunneling overhead.
- 📡 Latency-to-Distance Calculator — Convert ping latency to max possible distance. Bounded by speed of light.
Why this tool
vs typical free network-tools sites
| NetToolset | Typical free site | |
|---|---|---|
| Price | Free | Free |
| Signup required | No | Often (for advanced features) |
| Ads inside the tool | No | Yes (banner + interstitial) |
| Logs your IP / queries | No | Yes (often resold) |
| Data sent to a server | Math runs in browser; lookups hit Cloudflare DoH directly | Yes (all goes through their server) |
| Open source | Yes | No |
| Bookmarkable URL per tool | Yes | Mixed |
| Multilingual | EN / ES / PT / FR / DE | Usually EN only |
| Loads in under 1s | Yes (static) | Often slow (ad tracking) |