FreeBSD 12 – Common Problem 003 – Network Interface Does Not Come Up After Reboot

📖 ~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 boots but has no IP address, breaking SSH and service discovery.

Environment & Reproduction

After kernel or NIC driver updates, `em0`/`re0` may stay down until manual `ifconfig up`.

Root Cause Analysis

Incorrect `rc.conf` entries, interface name changes, or missing default route settings are common causes.

Quick Triage

Confirm detected interfaces and startup config.

ifconfig -l
ifconfig -a
grep -E 'ifconfig_|defaultrouter' /etc/rc.conf

Step-by-Step Diagnosis

Compare expected NIC name with boot logs and rc scripts.

dmesg | grep -E 'em|re|igb|ix'
service netif status
service routing status

Solution – Primary Fix

Set persistent network values and restart network services.

sysrc ifconfig_em0='DHCP'
sysrc defaultrouter='192.168.1.1'
service netif restart && service routing restart

Solution – Alternative Approaches

For static addressing, define `ifconfig_em0=’inet 192.168.1.20/24’` and optional `ipv6_defaultrouter`.

Verification & Acceptance Criteria

Reboot test confirms interface auto-up, valid route table, and stable SSH connectivity.

Rollback Plan

Restore previous `/etc/rc.conf` from backup and restart `netif`/`routing`.

Prevention & Hardening

Track interface names in CMDB and validate `rc.conf` via configuration management linting.

Related Errors & Cross-Refs

`No route to host`, `network unreachable`, missing default route in `netstat -rn`.

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

`rc.conf(5)`, `netif(8)`, `routing(8)`.