🟡 Medium   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: FreeBSD 15

📖 ~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

Interface comes up without valid lease, causing intermittent loss of connectivity.

Environment & Reproduction

Frequent on VM templates cloned with stale lease state.

ifconfig vtnet0
cat /var/db/dhclient.leases.vtnet0 2>/dev/null || true
service netif restart

Root Cause Analysis

Stale lease file, race timing, or upstream DHCP filtering prevents renewal handshake.

Quick Triage

Check link state, DHCP discover attempts, and lease file health.

ifconfig vtnet0
tcpdump -ni vtnet0 port 67 or port 68 -c 20
pgrep dhclient

Step-by-Step Diagnosis

Run dhclient in verbose mode and inspect resulting offers.

service netif stop vtnet0
rm -f /var/db/dhclient.leases.vtnet0
dhclient -d -v vtnet0
Illustrative mockup for freebsd-15 — terminal_or_shell
dhclient lease diagnostics — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Clear stale lease state and enforce DHCP startup via rc.conf.

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sysrc ifconfig_vtnet0="DHCP"
rm -f /var/db/dhclient.leases.vtnet0
service netif start vtnet0
Illustrative mockup for freebsd-15 — logs_or_journal
lease renewal success logs — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Assign static fallback network settings for critical infrastructure hosts.

sysrc ifconfig_vtnet0="inet 192.0.2.50 netmask 255.255.255.0"
sysrc defaultrouter="192.0.2.1"

Verification & Acceptance Criteria

Lease is acquired repeatedly after restart and route persists.

reboot
ifconfig vtnet0
netstat -rn

Rollback Plan

Restore prior interface config and lease file if required by network policy.

cp -a /etc/rc.conf.pre-dhcp-fix /etc/rc.conf
service netif restart

Prevention & Hardening

Monitor DHCP failure events and keep template cleanup scripts for lease files.

grep -i dhcp /var/log/messages | tail -n 50

May overlap with VLAN tagging issues and bridge misconfiguration in hypervisors.

Related tutorial: View the step-by-step tutorial for FreeBSD 15.

View all FreeBSD 15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

FreeBSD dhclient behavior and network startup documentation.

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