infrastructure/docs/incidents/2026-01-31-network-connectivity.md

Network Connectivity Issue

Date: 2026-01-31
Status: RESOLVED
Severity: Medium

Symptoms (Initial)

• DNS resolution failing (8.8.8.8 timeout)
• Cannot connect to local services via 192.168.31.2
• Git push to Gitea failing

Root Causes Identified

1. DHCP DNS misconfiguration - All VLANs were pushing 8.8.8.8 instead of gateway IP
2. Legacy IP references - Old 192.168.31.x IPs no longer valid after VLAN migration
3. Macvlan limitation - AdGuard on macvlan (br0) unreachable from host

Resolution

1. Updated MikroTik DHCP network settings:

   • VLAN 10: dns-server=192.168.10.1
   • VLAN 20: dns-server=192.168.20.1
   • VLAN 25: dns-server=192.168.25.1
   • VLAN 30: dns-server=192.168.30.1

2. Renewed DHCP lease on Unraid: dhcpcd -n br0

3. Updated NetAlertX config with correct IP (192.168.10.20)

Verification

• DNS now resolves via 192.168.10.1 (MikroTik gateway → AdGuard)
• Git push to Gitea working
• All services accessible

Lessons Learned

• After VLAN migration, update all hardcoded IPs
• DHCP DNS should point to gateway, not external servers
• Macvlan containers need shim interface for host communication