🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: FreeBSD 12

📖 ~1 min read

Table of contents
  1. Symptom & Impact
  2. Environment & Reproduction
  3. Root Cause Analysis
  4. Quick Triage
  5. Step-by-Step Diagnosis
  6. Solution – Primary Fix
  7. Solution – Alternative Approaches
  8. Verification & Acceptance Criteria
  9. Rollback Plan
  10. Prevention & Hardening
  11. Related Errors & Cross-Refs
  12. References & Further Reading

Symptom & Impact

Host loses IP after lease expiry, causing abrupt service interruption and failed remote access.

Environment & Reproduction

Appears after interface resets, DHCP server changes, or stale lease files.

cat /var/db/dhclient.leases.em0
ifconfig em0
ps aux | grep dhclient

Root Cause Analysis

dhclient process died, lease file became invalid, or firewall blocks DHCP renew traffic.

Quick Triage

Confirm process state and packet flow on UDP 67/68.

service netif status
pgrep -laf dhclient
tcpdump -ni em0 port 67 or port 68

Step-by-Step Diagnosis

Run dhclient foreground debug to inspect lease negotiation.

dhclient -d -v em0
rm -f /var/db/dhclient.leases.em0
dhclient em0
Illustrative mockup for freebsd-12 — terminal_or_shell
Checking DHCP lease and client status — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Recreate lease state and ensure dhclient starts consistently during interface bring-up.

Still having issues? Our Network Design team can diagnose and resolve this for you. Get in touch for a free consultation.

sysrc ifconfig_em0='DHCP'
service netif restart em0
service routing restart
Illustrative mockup for freebsd-12 — log_or_config
Restarting DHCP process and interface hooks — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Assign static addressing for critical servers or move renewals to redundant DHCP infrastructure.

Verification & Acceptance Criteria

Lease renews successfully and address remains stable beyond renewal interval.

ifconfig em0
cat /var/db/dhclient.leases.em0 | tail -n 30

Rollback Plan

Revert to previous static or DHCP setup if connectivity degrades after changes.

cp -a /etc/rc.conf /etc/rc.conf.rollback
service netif restart

Prevention & Hardening

Monitor lease expiry headroom and alert when renewal attempts fail repeatedly.

Commonly linked to VLAN tagging mismatches and pf rules blocking DHCP broadcast traffic.

Related tutorial: View the step-by-step tutorial for freebsd-12.

View all freebsd-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

dhclient(8), rc.conf(5), and FreeBSD network service documentation.

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