> For the complete documentation index, see [llms.txt](https://mudassirs46.gitbook.io/network-fundamentals/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mudassirs46.gitbook.io/network-fundamentals/port-roles-in-rstp.md). # Port Roles in RSTP ### Port Roles in [RSTP](https://app.gitbook.com/@mudassirs46/s/network-fundamentals/~/drafts/-MRZ8l67L5MHnaQIEh9W/rstp-rapid-spanning-tree) | Port Role | Function | | ------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | | **Root Port** | Same as STP's Root Port (Port with least Cost to reach the RB. Or else Least BID, Least Port Priority, Least Port Number) | | **Alternate Port** | Backup Root port if Root Port fails (same as Blocking Port (in discarding State)) | | **Designated Port** | Same as STP's Designated Port (Port with lowest Cost to reach the RB. Or else Lowest BID, Lowest Port Priority, Lowest Port Number) | | **Backup Port** | Backup Designated port if Designated Port fails (in discarding State) | | **Disabled Port** | Same as STP's Port (Administratively disabled) | | **Edge Port** | Ports connected to End devices (where STP is disabled generally) | #### Alternate Port: * Blocked ports are marked as Alternate Ports which are basically Backup Root Port. * If Root Port fails, this Alternate port becomes the RP immediately (generally in 1 sec) skipping the Listening & the Learning State. **Backup Port:** * The backup port role is only needed in the designs that are little unlikely today (E.g. A Switch connected to a HUB with 2 ports (in same Collision Domain) & HUB is connected to an End device). One from amongst these 2 ports will be Designated port and another port will be blocked marked as a backup port. ## Reference: * CCNA 200-301 OCG, Volume 1, Pg. 229-233 - Wendell Odom. * RST Notes * --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://mudassirs46.gitbook.io/network-fundamentals/port-roles-in-rstp.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.