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Troubleshooting Guides

IT & Network Troubleshooting Guides

Clear, step-by-step fixes for the problems that page you at 2am — across firewalls, switches, routers, servers, containers and databases. Each guide gives the real diagnosis and commands, then shows how Tech Matrix resolves it in about 60 seconds, grounded in your exact environment.

VPN & Firewall

FortiGate IPsec VPN tunnel down
Phase 1 vs Phase 2, the diagnose commands, and the fix.
Palo Alto IPsec VPN tunnel down
IKE/IPsec SAs, the proxy-ID trap, and the fix.
Cisco ASA site-to-site VPN
ISAKMP/IPsec, policy + PSK, and the NAT-exemption trap.
Juniper SRX IPsec VPN
IKE/IPsec, proxy-IDs, and the st0 route-based trap.
SonicWall site-to-site VPN not connecting
Proposals, the PSK, network objects, and the fix.

Switching & Routing

Cisco Catalyst high CPU
Interrupt vs process load, the offending process, the fix.
Cisco Nexus vPC inconsistency
Type-1 vs Type-2, and aligning the mismatch.
OSPF neighbor stuck in ExStart
The MTU mismatch signature and how to clear it.
BGP neighbor stuck in Active/Idle
What each state means and how to reach Established.

Load Balancing

F5 BIG-IP pool member down
It's the health monitor — check the port and the path.

Servers, OS & Virtualization

Linux high load average
Tell CPU-bound from I/O-bound and find the bottleneck.
Windows Server high memory
User-mode leak vs driver pool leak, and the fix.
VMware ESXi host disconnected
Restore the management path without disrupting VMs.
Proxmox cluster node offline
Corosync quorum and the cluster network, and the fix.

Containers

Kubernetes CrashLoopBackOff
describe + logs --previous to find the real cause.
Docker exit code 137 (OOMKilled)
Container limit vs host pressure, and the fix.

Databases

MySQL replication lag
Single-threaded apply, big transactions, indexes, disk.
PostgreSQL connections exhausted
Find the leak, kill idle-in-transaction, add PgBouncer.
Oracle ORA-12541: no listener
Listener down or wrong host/port, and the fix.

Cloud

AWS EC2 has no internet
Route to IGW, public IP, SG/NACL, NAT gateway.
Azure VPN gateway not connecting
Shared key, address spaces, IKE/IPsec policy.

Backup

Veeam backup job failed
Repository space, credentials, or VSS — and the fix.

Web & App

Nginx 502 Bad Gateway
Read the error log, check the backend, fix timeouts/buffers.

Compare

Juniper Marvis alternative
Vendor-neutral AI troubleshooting vs a single-vendor copilot.
ChatGPT for network troubleshooting
Where general LLMs fall short, and the alternative.

Skip the manual steps

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