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VPNs and IPsec
Tunnel wraps; encryption protects; policy limits.
| Topic | Remember |
|---|---|
| GRE | Course example of a tunnel without built-in confidentiality. |
| IKE | UDP 500 agrees settings/keys. |
| NAT-T | UDP 4500 through address translation. |
| ESP / AH | ESP can encrypt; AH does not. IP protocol 50/51, not ports. |
| Transport vs tunnel mode | Original addressing stays vs wrap the whole original packet. |
| Client-to-site vs site-to-site | One person enters vs two offices connect. |
| Split vs full tunnel | Which traffic uses the path. Not the same words as IPsec tunnel mode. |
| SSH vs Telnet | Door 22 has two keys; door 23 has an open window. Verify host keys. |