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To see the public IP address that internet services observe from a Linux machine, run curl -4 https://api.getpublicip.com/ip. Use -6 instead of -4 to check IPv6. These commands query an external service, so they report the address after your router, carrier-grade NAT, VPN, proxy, or other gateway has processed the connection—not necessarily an address shown by your local network tools.
What is an external IP address on Linux?
An external, public, or internet-facing IP address is the address a remote service sees as the source of your connection. It can be different from every address configured on your Linux interfaces because network address translation (NAT), a VPN, a proxy, a container network, or an upstream gateway may change the egress address.
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There may be two valid answers on a dual-stack host: one public IPv4 address and one public IPv6 address. Always state which address family you checked. A lookup over IPv4 does not prove what an IPv6-only destination would see.
How do I find my public IPv4 address with curl?
The quickest interactive check is a plain-text HTTPS request:
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curl -4 https://api.getpublicip.com/ipThe response should be a single IPv4 address. For quieter output with errors still displayed, use:
curl -4 -sS https://api.getpublicip.com/ipThe -4 option forces IPv4, while -sS hides the progress meter but keeps useful error messages. HTTPS protects the request in transit and makes the endpoint dependency explicit.
Which plain-text services can curl query?
These alternatives are useful when one endpoint is unavailable or filtered. Their response formats and availability can change, so use the documented plain-text response rather than assuming every service returns identical metadata.
| Endpoint | Example command | Typical use |
|---|---|---|
| api.getpublicip.com/ip | curl -4 -sS https://api.getpublicip.com/ip |
HTTPS, forced IPv4, one-line result |
| ifconfig.me | curl -s https://ifconfig.me |
Simple curl fallback |
| api.ipify.org | curl https://api.ipify.org |
Plain-text lookup |
| icanhazip.com | curl https://icanhazip.com |
Plain-text lookup |
| ifconfig.co | curl https://ifconfig.co |
Alternative lookup service |
Third-party lookup services are dependencies: the command fails if DNS, routing, firewall policy, TLS validation, or the service itself is unavailable. For a diagnostic, compare two independent endpoints instead of treating one response as infallible.
How do I check my public IPv6 address?
Force the IPv6 path with:
curl -6 https://api.getpublicip.com/ipIf the host has working IPv6, the response should be an IPv6 address. A dual-stack machine can return different addresses for -4 and -6; that is expected because they use separate protocol stacks and may follow different gateways.
The same family selection is available with Wget:
wget -6 -qO- https://api.getpublicip.com/ipIf IPv6 fails while IPv4 succeeds, check local IPv6 configuration, the default IPv6 route, firewall rules, and whether the network actually provides IPv6 service. Do not “fix” an IPv6 result by replacing it with IPv4 when the application specifically requires IPv6.
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How can I find the external IP without curl?
GNU Wget can print the response directly when curl is not installed:
wget -qO- https://api.getpublicip.com/ip-q suppresses progress output and -O- writes the downloaded data to standard output. Add -4 or -6 when the address family matters:
wget -4 -qO- https://api.getpublicip.com/ip
wget -6 -qO- https://api.getpublicip.com/ipThis is particularly convenient in a minimal recovery shell or a server image that includes Wget but not curl. As with curl, validate that the returned content is the documented address format before feeding it to another program.
How do I find my public IP with dig when HTTP is blocked?
DNS-only methods work when outbound DNS is available but HTTP requests are restricted. OpenDNS provides a resolver query that returns the caller’s address:
dig +short myip.opendns.com @resolver1.opendns.comA Google Public DNS variant is:
dig TXT +short o-o.myaddr.l.google.com @ns1.google.comThe first command normally prints an address directly. The TXT query may include quotation marks because DNS represents the answer as a text record; remove only presentation characters if a script needs a bare value.
These commands avoid an HTTP request, but they still depend on DNS reachability, the selected resolver, and network policy. Resolver-based answers can also describe the DNS path rather than the path used by a separate application. When diagnosing an unusual result, compare a DNS answer with an HTTPS lookup.
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What is the difference between a public IP and a local IP on Linux?
Local commands show addresses assigned to interfaces on the machine. They do not, by themselves, reveal the address a remote internet service sees.
hostname -I # space-separated local addresses
ip -4 addr show # local IPv4 addresses
ip -6 addr show # local IPv6 addresseshostname -I may list several addresses, including loopback exclusions, private LAN addresses, virtual interfaces, and container-related addresses. The ip utility exposes the addresses on each interface, along with enough context to identify which device owns them.
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| Question | Command or method | What it tells you |
|---|---|---|
| What addresses are configured locally? | ip -4 addr show, ip -6 addr show, or hostname -I |
Interface assignments on this Linux host |
| What public IPv4 does an internet service see? | curl -4 ... or wget -4 ... |
IPv4 egress address after gateways and NAT |
| What public IPv6 does an internet service see? | curl -6 ... or wget -6 ... |
IPv6 egress address for that path |
| What address does a DNS resolver infer? | dig ... |
Address observed through the chosen DNS method |
Private RFC 1918-style addresses such as 192.168.x.x, 10.x.x.x, and 172.16.x.x are normally LAN addresses. They are not routable as your public identity on the open internet.
Why does the address differ from my router or another website?
Different tests can legitimately use different egress paths. A VPN may supply its own public address; a proxy reports the proxy’s address; a container may exit through a host or orchestration gateway; and a multi-homed server may select different interfaces according to routing policy.
Carrier-grade NAT
If the address returned by an external service does not match your router’s WAN address, your ISP may be using carrier-grade NAT (CGNAT). CGNAT adds another translation layer, can share one public address among multiple customers, and prevents unsolicited inbound connections according to Jeremy Branson, a Network Engineer at GetPublicIP, in information updated September 29, 2026: “If your public IP doesn’t match your router’s WAN address, your ISP is using carrier-grade NAT (CGNAT), which blocks inbound connections.”
CGNAT is different from ordinary home NAT because you may not control the upstream translation. Port forwarding on your own router cannot create an inbound path through an ISP-managed NAT layer.
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Routing and interface selection
On a host with several interfaces, inspect routes when results seem inconsistent:
ip route
ip -6 routeThe route chosen for the lookup determines which interface, gateway, VPN tunnel, or namespace supplies the source path. Run the test in the same network namespace and service context as the application you are troubleshooting; a host shell and a container shell can have different egress addresses.
How do I automate a public-IP lookup safely?
For a shell script that needs one IPv4 value, capture the plain-text response and check the command status before using it:
public_ip=$(curl -4 -sS https://api.getpublicip.com/ip) || {
printf 'Public IP lookup failedn' >&2
exit 1
}
printf 'Public IPv4: %sn' "$public_ip"Use -6 when the script’s contract is IPv6. Keep the endpoint’s response format documented; if a service returns metadata or multiple lines, parse its documented field rather than assuming the first line is an address.
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- Keep the endpoint on HTTPS when supported.
- Set a timeout in unattended jobs so a hung network request cannot stall the whole script.
- Validate the result before inserting it into firewall rules, DNS records, or configuration files.
- Avoid writing the address to public logs; it identifies the network egress point even though it is not usually a secret credential.
- Cache only when your use case tolerates stale data. Residential and mobile addresses can change.
Which Linux method should I choose?
| Situation | Recommended method | Reason and limitation |
|---|---|---|
| One-time IPv4 check | curl -4 -sS https://api.getpublicip.com/ip |
Short, readable HTTPS command; requires curl and HTTP access |
| One-time IPv6 check | curl -6 -sS https://api.getpublicip.com/ip |
Forces IPv6; fails if the host has no usable IPv6 path |
| curl unavailable | wget -qO- ... |
Uses Wget’s standard-output mode |
| HTTP blocked but DNS works | dig +short myip.opendns.com @resolver1.opendns.com |
DNS-only; depends on resolver policy and DNS reachability |
| Need to inspect local interfaces | ip -4 addr show or ip -6 addr show |
Shows local assignments, not the public egress address |
| Diagnosing VPN, NAT, or routing | Run forced-family HTTPS and DNS checks, then inspect routes | Reveals whether path and resolver observations disagree |
What should I check when every lookup fails?
- Confirm the binary exists with
command -v curl,command -v wget, orcommand -v dig. - Check name resolution separately. If hostnames do not resolve, inspect the system resolver configuration and DNS reachability.
- Test the address family explicitly. A failed default request may be trying IPv6 when only IPv4 works, or the reverse.
- Check the default routes with
ip routeandip -6 route. - Review firewall, proxy, captive-portal, and egress-filter rules. Corporate and cloud networks often permit DNS while blocking arbitrary HTTPS.
- Compare two endpoints or an HTTPS result with a DNS result. A single service outage should not be mistaken for a missing public address.
If the machine is intentionally offline, there is no reliable local command that can discover the internet-facing address without an observation point outside the machine. In that case, inspect the upstream router or network provider’s management interface, recognizing that CGNAT can make the router’s WAN value differ from the address seen by websites.
What does finding the address prove—and what does it not prove?
A lookup proves the source address observed by that particular service over that particular protocol and route at that moment. It does not prove that the address is static, that inbound connections are possible, that every website will see the same value, or that IPv4 and IPv6 use the same gateway.
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For a server-access problem, pair the lookup with route inspection and an inbound test from an independent network. For an allowlist, record the address family, timestamp, and network path so a later address change is not confused with a firewall regression.
Frequently Asked Questions
Can I find my external IP address with no internet connection?
Not reliably from the Linux host alone. An external address is defined by what an outside service or upstream gateway observes, so an offline machine can only show configured local addresses or information supplied by its router or provider.
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Is my public IP address permanent?
That depends on the connection and provider. Dynamic residential, cellular, and many cloud egress addresses can change after reconnects or policy changes; a static assignment is a separate service and should be verified with the provider rather than inferred from one lookup.
Why does a browser show a different IP than my terminal?
The browser may use a VPN, proxy, secure DNS setup, split tunnel, or a different address family from the shell command. Compare the browser’s network path with forced curl -4 and curl -6 tests, and check whether the browser is running inside a separate container or profile.
Can I host a game server behind CGNAT?
Direct inbound port forwarding generally will not work through an ISP-managed CGNAT layer. Ask the provider for a public or static address, use an approved relay or tunnel, or host the service on a network where inbound routing is available.
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