# Generic Routing Encapsulation Generic Routing Encapsulation is a protocol, standard, or security technology recorded in [[Scanned_20260730-1706|Scanned_20260730-1706]]. In the reconstruction, GRE carries the tunneled payload. ## Historical and Technical Context [[Point-to-Point Tunneling Protocol|PPTP]] tunnels PPP over IP through a TCP control connection and GRE-carried data; RFC 2637 describes it as an informational vendor-consortium protocol and notes the standards-track movement toward L2TP ([RFC 2637](https://www.rfc-editor.org/info/rfc2637/)). [[Generic Routing Encapsulation|GRE]] carries the tunneled payload. [[Microsoft Point-to-Point Encryption|MPPE]] encrypts PPP payloads. The notebook's “PPP ALG” in the third paragraph is likely a slip for “PPTP ALG.” ## Role in Scanned_20260730-1706 This is a faithful study note on why PPTP cannot be handled solely by opening TCP 1723: the firewall must associate the separate GRE data path with the negotiated control session. ## Notebook Evidence - [[Scanned_20260730-1706|Scanned_20260730-1706]], PDF page 26: PPTP ALG. **Evidentiary status:** The page occurrence and transcription are notebook evidence. Technical identification follows the source reconstruction’s cited research. Co-occurrence does not by itself prove ownership, deployment, or a direct operational relationship. ## Relationships and Overlays On the cited page or pages, Generic Routing Encapsulation appears with [[Microsoft Point-to-Point Encryption|MPPE]], [[Point-to-Point Tunneling Protocol|PPTP]]. These are page-level or reconstruction-level relationships, not automatic claims of dependency. ## Cross-Notebook Significance This note supplies a concrete network-policy or evidence mechanism beneath the AIOps, security-operations, and governance concerns in [[Scanned_20260730-1802|Scanned_20260730-1802]]. It shows how dynamic state is created, observed, and retained at the protocol boundary. ## Missed Signals and Open Leads The IPv6/MPPE line compresses distinct concepts and deserves comparison against the exact Junos manual version used. ## Sources - [[Scanned_20260730-1706|Scanned_20260730-1706]], especially PDF page(s) 26. - `Scanned_20260730-1706.pdf`, cited as a plain archival filename; the PDF is not linked from `wiki-notes`. - External research citations used for identification remain preserved in the source reconstruction. - [RFC 2637](https://www.rfc-editor.org/info/rfc2637/)