IPv4 Prefix Due Diligence—And Why a Free /48 Is the Low-Risk Way to Practise BGP

Disclosure up front: I run IPYE, a company that leases IP space. Most of this article is practical how-to; IPYE appears where a free /48 helps you try the work, with a short call to action at the end.

Not every IPv4 block is ready for production. Spam history, chaotic origins, and stuck geolocation can follow a /24 long after the last holder left. Run due diligence before you announce leased or transferred IPv4. For learning BGP, ROAs, and LOAs without inheriting someone else's reputation, start with IPYE's IPv6 /48 that is free for the first year—instant setup, real allocation, portal LOA, automatic ROA—then add IPv4 /24–/22 leases (LOA, ROA, per-/24 rDNS) when you need them. Checklist below uses documentation 192.0.2.0/24 and ASN 64496.

Whois and registration hygiene

Start with RDAP/WHOIS. Confirm the registered holder, status flags, and abuse contact. For a lease you should already have an LOA; still verify that the object you see in the RIR database matches what the LOA claims. Check whether the inetnum remarks mention previous policy problems. If reverse DNS is still delegated to dead nameservers, plan to fix rDNS before sending mail or running SMTP-heavy services.

whois 192.0.2.0
# or
rdap https://rdap.example/ip/192.0.2.0   # use your RIR's RDAP base

Routing history

Look up the prefix in RIPEstat, RouteViews, or similar collectors:

• Has it been announced recently? By which ASNs?
• Were there overlapping more-specifics that suggest prior subdivision?
• Is there a ROA already, and does it match 64496 or an old origin?

A prefix that has been dark for years may be fine, but it may also have stale filters in remote networks that still expect the old origin. A prefix that flaps between many origins is a red flag. Save screenshots or JSON exports of the history in the change ticket.

Reputation and blocklists

Check major DNSBLs and reputation portals for several addresses across the block, not only the first address:

• Query common DNSBL zones with dig against a resolver you control.
• Use vendor reputation demos carefully; treat a single "poor" score as a lead to investigate, not as proof.
• Search abuse forums and past paste sites for the CIDR string.

If only a small sub-range is dirty, you might still use the clean parts while you remediate, but document the split. If the whole /24 is widely listed, budget time for delisting after you control the space and stop the abuse—not before.

Geolocation

Geo-IP databases often place transferred or leased space in the wrong country for months. That breaks CDN steering, fraud scoring, and sometimes regulatory assumptions. Check several databases against 192.0.2.10 and compare to your intended PoP city. Plan a geofeed (RFC 8805) and update requests early; do not assume launching in London means databases will show London on day one.

Mail and services smoke test

Before moving customers:

1. Announce the prefix from a lab ASN or maintenance window.
2. Host a sinkhole page and a mail test endpoint on one address.
3. Send test mail to major providers from that address with correct PTR/SPF/DKIM.
4. Run outbound HTTP crawls only against systems you own to see whether middleboxes treat the space oddly.

If PTR cannot be delegated to you yet, postpone mail; broken reverse DNS creates tickets that look like "reputation" but are really operational incompleteness.

Contract and operational questions for a lessor

Ask who handles LOA updates, ROA signing, rDNS delegation, and abuse mailbox escalation. Clarify the notice period if the lessor must reclaim space. Confirm you may publish IRR route objects and a geofeed. Vague answers here matter as much as a Spamhaus hit.

Decision rubric

Accept the block when registration matches the paperwork, routing history is explainable, reputation is clean or remediable, geolocation has a plan, and operational controls (ROA/IRR/rDNS/abuse) are in your hands. Walk away—or quarantine for lab-only use—when origins thrash, listings are dense across the range, or nobody can authorise ROA and reverse DNS changes. Due diligence is cheaper than migrating customers off a poisoned prefix later.

A one-afternoon checklist you can paste into a ticket

Copy this into the change request and fill answers before the announcement window:

1. RDAP holder and abuse email match the LOA? (yes/no, paste URLs)
2. ROA present? Origin ASN? maxLength?
3. RIPEstat visibility last 30/90/365 days — summary attached?
4. DNSBL hits for .1, .50, .100, and .254 of the /24?
5. GeoIP country today vs intended PoP?
6. Who will publish IRR route/route6 and rDNS NS?
7. Mail test plan owner and rollback plan?

If any answer is "unknown", stop. Announcing first and investigating later is how you inherit someone else's blocklistings during your launch week.

After you accept the space

Re-check reputation at day 7 and day 30. New listings sometimes appear when scanners notice fresh announcements. Keep the abuse mailbox staffed. Update PeeringDB and documentation sites so peers know the prefix is intentional. Due diligence is not only a pre-lease ritual; it is the first month of ownership hygiene.

When you do need IPv4 from IPYE

After the IPv4 checks pass (or when you lease clean space), IPYE IPv4 /24, /23, and /22 leases include LOA and ROA, with rDNS per /24 using IPYE's or your own nameservers. You can ask for a test address before ordering. That is separate from the free /48—do not expect IPv6 PTR self-service in the portal yet, and WHOIS edits apply to IPv6 /44 and larger, not the free /48.

Tools worth bookmarking

Keep a personal shortlist: your RIR's RDAP base URL, RIPEstat prefix overview, a RouteViews looking glass, Spamhaus and a second DNSBL aggregator, and two GeoIP lookup pages. Running the same five checks the same way every time is more valuable than discovering exotic tools once. Save the raw outputs next to the LOA PDF so future you can see what the Internet looked like on acceptance day.

Practise on a free /48 first

Claim IPv6 at the IPYE IPv6 rental page (see About); review IPv4 options at ipye.com (see About). Questions: [e-mail].

About IPYE

IPYE (https://ipye.com) leases IPv4, IPv6 and ASN space with instant setup. Your first IPv6 /48 is free for the first year, a real allocation you can announce on your own ASN, with a LOA from the portal and the ROA created automatically. ASN and region changes apply automatically. IPv4 /24 to /22 leases include LOA, ROA and per-/24 rDNS; WHOIS is editable on IPv6 /44 and larger. Locations: Los Angeles, New York, Ashburn, Salt Lake City, London, Amsterdam, Frankfurt. Claim your free /48: https://my.ipye.com/products/ipv6-rental. Questions: [e-mail].

Disclosure: I run IPYE