Add accel-ppp PPPoE server tutorial (#2015)

docs/guides/network/accel-ppp_pppoe_server.md

@@ -0,0 +1,137 @@
+---
+title: accel-ppp PPPoE Server
+author: Neel Chauhan
+contributors:
+tested_with: 9.3
+tags:
+  - network
+---
+
+# OpenBGPD BGP Router
+
+## Introduction
+
+PPPoE is a protocol used primarily by DSL and fiber-to-the-home ISPs where customers are authenticated with a username and password combo. PPPoE is used in countries where an incumbent ISP is requierd to share their network with other ISPs as customers can be routed via a domain name to the desired ISP.
+
+[accel-ppp](https://accel-ppp.org/) is a Linux kernel-accelerated implementation of PPPoE and related protocols such as PPTP, L2TP, and others.
+
+## Prerequisites
+
+- A server with two network interfaces
+- A client router or machine speaking PPPoE
+
+## Installing accel-ppp
+
+As accel-ppp is not in the default repositories, we first install the required packages to build it:
+
+```bash
+dnf install -y rpm-build make cmake gcc git openssl-devel pcre-devel kernel-modules-extra
+```
+
+Subsequently, clone the accel-ppp source code to a folder:
+
+```bash
+git clone https://github.com/accel-ppp/accel-ppp.git /opt/accel-ppp
+mkdir /opt/accel-ppp/build
+cd /opt/accel-ppp/build/
+```
+
+Next, we need to build accel-ppp (Note: If you're running Rocky Linux 8.x, substitute in `Centos8` for `Centos9`):
+
+```bash
+cmake -DCMAKE_INSTALL_PREFIX=/usr -DCPACK_TYPE=Centos9 ..
+make
+```
+
+Finally, we will build an `rpm` package and install it:
+
+```bash
+cpack -G RPM
+rpm -ivh accel-ppp.rpm
+```
+
+## Setting up accel-ppp
+
+First, we need to enable IP forwarding:
+
+```bash
+echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf
+sysctl -p
+```
+
+Then, add the following to `/etc/accel-ppp.conf`:
+
+```bash
+[modules]
+log_file
+pppoe
+auth_mschap_v2
+auth_mschap_v1
+auth_chap_md5
+auth_pap
+chap-secrets
+ippool
+
+[core]
+log-error=/var/log/accel-ppp/core.log
+thread-count=4
+
+[ppp]
+ipv4=require
+
+[pppoe]
+interface=YOUR_INTERFACE
+
+[dns]
+dns1=YOUR_DNS1
+dns2=YOUR_DNS2
+
+[ip-pool]
+gw-ip-address=YOUR_GW
+YOUR_IP_RANGE
+
+[chap-secrets]
+gw-ip-address=YOUR_GW
+chap-secrets=/etc/chap-secrets
+```
+
+Replace the following information:
+
+- **YOUR_INTERFACE** with the interface listening for PPPoE clients.
+- **YOUR_DNS1** and **YOUR_DNS2** with the DNS servers to hand out to clients.
+- **YOUR_GW** is the server's IP address for PPPoE clients. This **must** be different from the server's WAN-facing IP address or default gateway.
+- **YOUR_IP_RANGE** with the IP ranges to hand out to clients. This can be an IP range like X.X.X.Y-Z or in CDIR format such as X.X.X.X/MASK.
+
+Subsequently, let us add a barebones `/etc/chap-secrets` file:
+
+```bash
+user	*	password	*
+```
+
+You can add more users with additional lines by replacing `user` and `password` with the desired username and password.
+
+## Configuring a PPPoE client:
+
+Once the PPPoE server is set up, we can start adding PPPoE clients. The author likes to use [MikroTik CHR](https://help.mikrotik.com/docs/display/ROS/Cloud+Hosted+Router%2C+CHR) as their go-to testing PPPoE client so we will use that.
+
+Once we installed MikroTik CHR onto a system connected to the same Ethernet network as the PPPoE server's listening interface, we will configure PPPoE:
+
+```bash
+[admin@MikroTik] > /interface pppoe-client
+[admin@MikroTik] > add add-default-route=yes disabled=no interface=ether1 name=pppoe-out1 \
+    password=password user=user
+```
+
+If everything is working properly we should get an IPv4 address:
+
+```bash
+[admin@MikroTik] > /ip/address/print
+Flags: D - DYNAMIC
+Columns: ADDRESS, NETWORK, INTERFACE
+#   ADDRESS      NETWORK   INTERFACE 
+0 D 10.0.0.1/32  10.0.0.0  pppoe-out1
+```
+
+## Conclusion
+
+PPPoE often gets a bad rap and it's easy to see why: you need to configure usernames and passwords manually. Despite that, it allows for security to a Layer 2 broadcast domain in ISP scenarios where requiring 802.1X or MACSEC would be undesirable, for instance to allow customer-owned routers or static IP addresses. And now you are your own mini-ISP, congratulations!