The Scenario
You're a network operations engineer. The quarterly audit starts Monday and the checklist says line one: "device and service inventory with hostname resolution." Your manager handed you a routing table export Friday at 4 PM — 1,000 IP addresses in an Excel workbook, one per row.
You need the reverse-DNS hostname for each. You also need to flag any IP that has no PTR record, because those are the ones the audit team will ask about first.
You have a terminal open on the other monitor. You know you could run nslookup in a loop. You also know that 1,000 nslookup calls in a shell loop will take a while to format into something that aligns with the workbook columns.
The bad version:
- Write a shell script: loop column A, run nslookup, capture the hostname line, output tab-separated.
- Realize the output varies depending on whether nslookup resolves or returns "NXDOMAIN" — add conditional logic.
- Import the output into Excel, fix the row alignment because the shell script added blank lines for failed lookups.
- Manually label empty hostname cells as "No PTR record."
The audit is Monday. You have a weekend you'd rather not spend debugging a shell script's output formatting.
The Easy Way: One Prompt in SheetXAI
SheetXAI is an AI agent inside your Excel workbook. Through its IPinfo integration, it resolves reverse-DNS hostnames for every IP in your list and flags the empty results automatically.
Open the SheetXAI sidebar and paste:
For each IP address in column A, use IPinfo to look up the reverse-DNS hostname and write it to column B. Flag rows where the hostname is empty as "No PTR record" in column C.
What You Get
- Column B: resolved hostname (e.g., "mail.acme.com" or "db-prod-02.internal.example.net")
- Column C: "No PTR record" for any IP that returned an empty hostname, blank for rows that resolved
- All 1,000 rows completed in one operation — no shell script, no import, no realignment
What If the Data Is Not Quite Ready
IPs are in CIDR notation and I need to strip the prefix first
Column A contains IPs in CIDR notation (e.g., 203.0.113.5/24). Strip the subnet prefix from each cell, look up the reverse-DNS hostname for each using IPinfo, and write the hostname to column B. Flag empty hostnames as "No PTR record" in column C.
I want to classify devices by hostname pattern for the audit inventory
Look up the reverse-DNS hostname for all IPs in column A using IPinfo and write to column B. In column C, classify each hostname: write "Mail server" if the hostname contains "mail" or "smtp," "Database" if it contains "db" or "mysql" or "pg," "Web server" if it contains "web" or "www" or "nginx," and "Unknown" for everything else. Leave blank if no PTR record exists.
I only need to see devices on our internal domain
Resolve reverse-DNS hostnames for all IPs in column A via IPinfo, write to column B. Filter to only rows where the hostname ends in ".acme.internal" or ".acme.net" and write those rows — IP and hostname — to a new worksheet called "Internal Devices."
Full audit inventory: resolve, classify, flag anomalies, and summarize
Column A has 1,000 IPs from the routing table. Resolve reverse-DNS hostnames via IPinfo, write to column B. Classify each by device type based on hostname keywords (mail, db, web, vpn, fw for firewall) and write the classification to column C. Flag any IP where the hostname is empty as "No PTR" in column D. Flag any IP where the classification is "Unknown" but the hostname is not empty as "Review" in column D. Write a count-per-classification summary to a new worksheet called "Audit Inventory Summary."
Complete audit inventory before Monday morning.
Try It
Get the 7-day free trial of SheetXAI and open any Excel workbook with a network inventory or routing export, then ask it to resolve hostnames via IPinfo and classify your devices for the audit. See also abuse contact lookup for incident response or fast ASN enrichment for large logs. Hub: IPinfo + Excel.