Troubleshooting · VPN
VPN will not connect
Remote access fails to establish, or connects but cannot reach internal resources.
Work through these in order
- 01
Separate authentication from tunnel establishment
Check the gateway log: did the negotiation fail, or the credential or MFA step?
- 02
Check the client and gateway versions
Version mismatches after a gateway upgrade are a common cause of sudden mass failures.
- 03
Check certificate validity
Gateway certificate, client certificate and CA chain expiry all present as connection failures.
- 04
If connected but nothing works
Check pushed routes, split tunnel configuration, DNS servers pushed to the client, and per group ACLs.
- 05
Check capacity and licensing
Concurrent session limits produce failures that appear intermittent and user specific.
- 06
Check MTU
Sessions that establish but hang on large transfers point to fragmentation issues.
Background reading
VPN
A virtual private network carries private traffic across untrusted networks inside an authenticated, encrypted tunnel.
Certificates & PKI
The hierarchy of certificate authorities, policies and lifecycle processes that issue and validate digital identities.
Multi Factor Authentication
Requiring two or more independent factors, something you know, have or are, before granting access.
DNS
The Domain Name System is the distributed, hierarchical directory that resolves names to addresses and service records for nearly every other service.