Port 4500 (IPsec NAT traversal)
Carries IPsec traffic through NAT, alongside IKE on 500.
- Transport
- UDP
- Internet exposure
- Public by design
Normally public, but keep the software patched and hardened.
Security notes
- Same exposure as the VPN gateway it belongs to.
When it shows up in your logs
Probing alongside 500 is VPN discovery.