What the 0X000025EB error actually means
When you see 0X000025EB, the resolver hit a CNAME chain that points back to itself. Think of it as a DNS version of ln -s a a — the alias never resolves to an actual A record. The resolver walks the chain, hits the same name again, and gives up with this error after the loop counter trips.
This shows up in two typical places: when you're querying a hostname that someone misconfigured in their DNS zone, or when you're testing your own domain after a botched alias change. I've seen it most often right after someone changes a CDN CNAME and leaves the old target as a leftover.
Here's the thing — most of the time your DNS records are fine. The loop is being cached somewhere between you and the authoritative server. That's why the fixes go from simplest to most invasive.
Fix 1: The 30-second fix — flush your local DNS cache
Your OS caches DNS responses aggressively. If a previous query returned a looped chain, that garbage can sit in cache long after the server-side record is corrected. Flush it and retry.
On Windows 10 or 11, run this in an admin command prompt:
ipconfig /flushdnsOn macOS (Catalina or later):
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponderOn Linux, it depends on your resolver. If you use systemd-resolved:
sudo resolvectl flush-cachesAfter flushing, try your query again. If you're still hitting 0X000025EB, move on — the problem isn't in your local cache.
Fix 2: The 5-minute fix — check your DNS records for a loop
Now you're going to verify the actual records. The most common loop pattern is www.example.com pointing to example.com, and then example.com pointing back to www.example.com. That's a textbook CNAME cycle.
Log into your DNS provider's control panel (Cloudflare, Route 53, GoDaddy — same idea everywhere). Look for any CNAME records where the target resolves back to the name. Here's what to check:
- Does
wwwpoint to@(the bare domain) via a CNAME? If so, does the bare domain have a CNAME pointing towww? That's a loop. - Is there a CNAME pointing to a hostname that no longer exists, but the DNS provider still serves a stale answer? That can simulate a loop.
- Did you recently switch CDNs? A leftover CNAME from the old provider pointing to the new one can create a chain that ends up looping.
Fix any obvious cycles. Change one of the CNAMEs to an A record, or remove the redundant alias. Then wait for propagation — that can take a few hours depending on your TTL. If you set short TTLs (300 seconds or less) before making changes, you'll see results faster.
Fix 3: The 15+ minute fix — trace the chain manually with dig
If you've flushed cache and your records look clean, the loop might be happening on an intermediate DNS server — your ISP's resolver or a public one like 8.8.8.8. Those servers cache too, and they might be serving a poisoned chain.
Use dig to trace the exact chain. On Windows, install BIND tools or use nslookup in debug mode, but dig is cleaner. Run this:
dig +trace example.comThat walks the query from the root servers down to the authoritative nameserver. Watch for where the CNAME appears. If you see example.com. CNAME example.com. — that's the loop. The output will show you exactly which server is handing out the bad data.
If the authoritative server (the last one in the trace) is clean, but you still get the error when querying through a public resolver, try a different resolver:
dig @1.1.1.1 example.comIf Cloudflare's resolver works but Google's doesn't, the issue is Google's cache. Wait for it to expire, or just switch your system's DNS to 1.1.1.1 temporarily.
Why this error is almost never a server outage
Here's the thing — 0X000025EB is a resolver-side error, not a server-side one. The authoritative server isn't down; it's serving a looped response. So don't waste time checking uptime monitors. The issue is in the DNS configuration or a cache somewhere.
One real-world case: a client had a subdomain api.example.com CNAME'd to loadbalancer.example.com, and someone later added a CNAME for loadbalancer.example.com pointing back to api.example.com — probably to "round-robin" traffic, which doesn't work that way. Their internal resolver cached the loop for the full TTL (3600 seconds), so even after fixing the records, they saw the error for an hour. The flush fixed it immediately.
Prevention: keep CNAME chains short and flat
DNS specs allow CNAME chains up to a certain depth, but every link adds a round trip and a chance for a loop. Best practice is to point CNAMEs directly to an A record, not to another CNAME. If you're using a CDN, point your hostname to the CDN's target (which is usually a CNAME to their infrastructure) — that's fine. Just don't chain your own aliases on top of each other.
Also, set TTLs to 300 or lower when you're planning changes. That way, when you break something, the fix propagates in five minutes instead of five hours.
When to call your DNS provider
If you've done all three fixes and still get the error, there's a chance your DNS provider has a stale glue record or a broken DNSSEC chain. That's rare, but it happens. Contact their support and show them the dig +trace output. They'll see the exact point of failure.
One last check — if you're using a wildcard CNAME like *.example.com, make sure it doesn't match the target. A wildcard can unexpectedly loop when a specific subdomain's CNAME points back to the wildcard name. That's sneaky and easy to miss.
You'll resolve this. It's a configuration problem, not a hard outage. Start with the flush, check your records, and only pull out dig if you need the forensic detail.