PPPoE Configuration

Configure PPPoE subscriber termination via accel-ppp.

Overview

The pppoe section configures the PPPoE server (accel-ppp), which:

Terminates PPPoE sessions from subscribers
Negotiates PPP protocol (LCP, IPCP)
Integrates with RADIUS for authentication and IP assignment
Applies per-subscriber QoS rules

accel-ppp is managed by abngd: it is unmasked and auto-started at boot when pppoe is enabled, and its configuration is rendered on commit. RADIUS authentication supports PAP, CHAP, and MS-CHAP (v1/v2). The rendered config does not emit a literal wildcard service-name, so clients that send an empty Service-Name are accepted.

PPPoE sessions appear in show subscribers. This works via accel-ppp's pppd-compat module: abngd renders the config with pppd_compat loaded and a [pppd-compat] section that runs ip-up / ip-down hook scripts (installed at /opt/athena-bng/etc/hooks/pppoe-up.sh and pppoe-down.sh). The hooks call abng-notify, which registers and clears the session in abngd.

Configuration Options

enabled

Enable or disable PPPoE (optional).

pppoe:
  enabled: true

Type: Boolean
Required: No
Default: false
Valid values: true, false

CLI:

abng# set pppoe enabled true

Note: Requires radius.servers to be configured.

ac_name

Access Concentrator name advertised in PPPoE (optional).

pppoe:
  ac_name: "AthenaBNG"

Type: String
Required: No
Default: "AthenaBNG"
Constraints: 1-64 characters

Purpose: Identifies the BNG in PPPoE PADO frames.

CLI:

abng# set pppoe ac_name "AthenaBNG"

mtu

Maximum Transmission Unit for PPP (optional).

pppoe:
  mtu: 1492

Type: Integer
Required: No
Default: 1492
Constraints: 1280-1500 bytes

Purpose: PPP MTU (Ethernet MTU 1500 - 8 bytes for PPPoE header).

CLI:

abng# set pppoe mtu 1492

mru

Maximum Receive Unit for PPP (optional).

pppoe:
  mru: 1492

Type: Integer
Required: No
Default: 1492
Constraints: 1280-1500 bytes

Purpose: Maximum size of PPP frames to receive.

CLI:

abng# set pppoe mru 1492

lcp_echo_interval

LCP Echo Request interval in seconds (optional).

pppoe:
  lcp_echo_interval: 30

Type: Integer
Required: No
Default: 30
Constraints: Positive integer (seconds)

Purpose: Keepalive interval for PPP link monitoring.

CLI:

abng# set pppoe lcp_echo_interval 30

lcp_echo_failure

LCP Echo Request failures before disconnect (optional).

pppoe:
  lcp_echo_failure: 3

Type: Integer
Required: No
Default: 3
Constraints: Positive integer

Purpose: Disconnect session after N failed echo requests.

CLI:

abng# set pppoe lcp_echo_failure 3

ipv6

Enable IPv6 dual-stack (IPv6CP) for PPPoE sessions (optional).

pppoe:
  ipv6: allow

Type: String
Required: No
Default: "deny"
Valid values: deny, allow, prefer, require

Value	Meaning
`deny`	IPv6CP disabled — sessions are IPv4-only (default)
`allow`	Negotiate IPv6 if the client requests it
`prefer`	Offer IPv6, falling back to IPv4-only if the client declines
`require`	Require IPv6CP — reject sessions that will not negotiate it

When set to anything other than deny, abngd renders accel-ppp with the ipv6_nd (Router Advertisements / RDNSS for the WAN /64) and ipv6_dhcp (DHCPv6 IA_PD for the delegated prefix) modules. Both the WAN prefix (Framed-IPv6-Prefix) and the delegated prefix (Delegated-IPv6-Prefix) come only from RADIUS — there is no local IPv6 pool, so a session whose RADIUS reply carries no IPv6 attributes comes up IPv4-only (fail-closed).

CLI:

abng# set pppoe ipv6 allow

See IPv6 / Dual-Stack for the full model.

ipv6_dns

IPv6 DNS resolvers advertised to subscribers via RA RDNSS / DHCPv6 (optional).

pppoe:
  ipv6: allow
  ipv6_dns:
    - "2606:4700:4700::1111"
    - "2001:4860:4860::8888"

Type: List of IPv6 addresses
Required: No
Default: Empty (advertise none)

Note: Only used when ipv6 is not deny.

CLI:

abng# set pppoe ipv6_dns ["2606:4700:4700::1111", "2001:4860:4860::8888"]

Example Configurations

Minimal PPPoE Configuration

pppoe:
  enabled: true

Uses all defaults:

AC Name: "AthenaBNG"
MTU/MRU: 1492
LCP Echo: 30s interval, 3 failures

Full PPPoE Configuration

pppoe:
  enabled: true
  ac_name: "AthenaBNG-01"
  mtu: 1492
  mru: 1492
  lcp_echo_interval: 30
  lcp_echo_failure: 3

Dual-Stack (IPv6) PPPoE Configuration

pppoe:
  enabled: true
  ac_name: "AthenaBNG-01"
  ipv6: prefer
  ipv6_dns:
    - "2606:4700:4700::1111"
    - "2001:4860:4860::8888"

Subscribers whose RADIUS profile returns Framed-IPv6-Prefix / Delegated-IPv6-Prefix come up dual-stack; those without come up IPv4-only. See IPv6 / Dual-Stack.

Configuration via CLI

Enable PPPoE

abng> configure
abng# set pppoe enabled true
abng# commit

Set AC Name

abng# set pppoe ac_name "MyBNG"
abng# commit

Set MTU/MRU

abng# set pppoe mtu 1492
abng# set pppoe mru 1492
abng# commit

Set LCP Parameters

abng# set pppoe lcp_echo_interval 60
abng# set pppoe lcp_echo_failure 5
abng# commit

Verification

View PPPoE Configuration

abng> show configuration | match "^pppoe:"
pppoe:
  enabled: true
  ac_name: AthenaBNG
  mtu: 1492
  mru: 1492
  lcp_echo_interval: 30
  lcp_echo_failure: 3

View PPPoE Sessions

abng> show subscribers pppoe
┌────┬───────┬──────────┬───────────────┬────────────┬──────────┐
│ ID │ Type  │ Username │ IP Address    │ Interface  │ Speed D/U│
├────┼───────┼──────────┼───────────────┼────────────┼──────────┤
│  1 │ PPPoE │ user1    │ 203.0.113.10  │ ppp0       │ 100M/40M │
│  2 │ PPPoE │ user2    │ 203.0.113.11  │ ppp1       │ 50M/20M  │
└────┴───────┴──────────┴───────────────┴────────────┴──────────┘

Check accel-ppp Logs

sudo journalctl -u accel-ppp -f

Integration with RADIUS

PPPoE requires RADIUS for authentication and IP assignment:

pppoe:
  enabled: true
  ac_name: "AthenaBNG"

radius:
  servers:
    - host: "10.255.0.10"
      secret: "your-secret"
  nas_identifier: "AthenaBNG"
  nas_ip_address: "10.255.0.1"

RADIUS attributes used:

User-Name — Subscriber username
User-Password / CHAP-Password — Subscriber credentials (PAP/CHAP/MS-CHAP)
Framed-IP-Address — Assigned IP address
Framed-IP-Netmask — Subnet mask
Framed-IPv6-Prefix — WAN /64 for IPv6 (dual-stack; advertised via RA/SLAAC)
Delegated-IPv6-Prefix — Delegated PD (e.g. /56) handed out via DHCPv6 IA_PD
Session-Timeout — Session timeout in seconds
Athena-Rate-Down / Athena-Rate-Up — Optional per-subscriber download/upload rates
Acct-Session-Id — Session ID for accounting

The two IPv6 attributes are honored only when pppoe.ipv6 is not deny, and are the sole source of a subscriber's IPv6 (no local pool). See IPv6 / Dual-Stack.

Integration with QoS

PPPoE sessions can have per-subscriber QoS rules:

qos:
  enabled: true
  default_down: "100mbit"
  default_up: "40mbit"
  default_overhead_profile: "pppoe_ethernet"

QoS is applied when:

PPPoE session is established
RADIUS returns rate attributes (Athena-Rate-Down, Athena-Rate-Up)
CAKE shaping is applied per subscriber — downstream on the PPP interface and upstream via a per-session IFB device

The subscriber's rate reaches abngd via the radattr file: accel-ppp writes the RADIUS reply attributes to <radattr-prefix>.<ifname> (configured radattr-prefix=/run/accel-ppp/radattr; the accel-ppp unit provides /run/accel-ppp via RuntimeDirectory=accel-ppp). The ip-up hook reads Athena-Rate-Down / Athena-Rate-Up from that file and passes them to abngd.

No rate = unmetered. A session whose RADIUS reply carries no rate attribute is reported unshaped; there is no implicit default rate.

Validation Rules

Field	Validation
`enabled`	Boolean
`ac_name`	1-64 characters
`mtu`	Integer 1280-1500
`mru`	Integer 1280-1500
`lcp_echo_interval`	Positive integer (seconds)
`lcp_echo_failure`	Positive integer
`ipv6`	One of: deny, allow, prefer, require
`ipv6_dns`	List of valid IPv6 addresses

Best Practices

AC Name — Use a descriptive name (e.g., "AthenaBNG-Brisbane")
MTU/MRU — Use 1492 for standard PPPoE (1500 - 8 byte header)
LCP Echo — Use 30s interval with 3 failures for standard keepalive
RADIUS — Always configure RADIUS servers before enabling PPPoE
QoS — Enable QoS for per-subscriber rate limiting
Monitoring — Monitor PPPoE session count and churn rate

Troubleshooting

No PPPoE Sessions Appearing

Check PPPoE is enabled: show configuration | match pppoe
Check VLAN demux is enabled: show configuration | match demux
Check VLAN interfaces are created: show vlans
Check RADIUS is reachable: radtest testuser testpass <radius-ip> 1812 <secret>
Check accel-ppp logs: journalctl -u accel-ppp -f

Sessions Disconnecting Frequently

Check LCP echo settings: show configuration | match lcp_echo
Check network stability: ping -c 100 <upstream-router>
Check RADIUS timeout: Increase lcp_echo_failure if RADIUS is slow
Check accel-ppp logs: journalctl -u accel-ppp -f

Sessions Not Getting IP

Check RADIUS is configured: show configuration | match radius
Test RADIUS: radtest testuser testpass <radius-ip> 1812 <secret>
Check RADIUS returns Framed-IP-Address
Check abngd logs: journalctl -u abngd -f

Next Steps

DHCP Configuration — DHCP/IPoE server settings
RADIUS Configuration — RADIUS servers and AAA
QoS Configuration — CAKE traffic shaping
IPv6 / Dual-Stack — dual-stack subscriber service
Configuration Overview — All configuration sections

Overview​

Configuration Options​

enabled​

ac_name​

mtu​

mru​

lcp_echo_interval​

lcp_echo_failure​

ipv6​

ipv6_dns​

Example Configurations​

Minimal PPPoE Configuration​

Full PPPoE Configuration​

Dual-Stack (IPv6) PPPoE Configuration​

Configuration via CLI​

Enable PPPoE​

Set AC Name​

Set MTU/MRU​

Set LCP Parameters​

Verification​

View PPPoE Configuration​

View PPPoE Sessions​

Check accel-ppp Logs​

Integration with RADIUS​

Integration with QoS​

Validation Rules​

Best Practices​

Troubleshooting​

No PPPoE Sessions Appearing​

Sessions Disconnecting Frequently​

Sessions Not Getting IP​

Next Steps​

Overview

Configuration Options

enabled

ac_name

mtu

mru

lcp_echo_interval

lcp_echo_failure

ipv6

ipv6_dns

Example Configurations

Minimal PPPoE Configuration

Full PPPoE Configuration

Dual-Stack (IPv6) PPPoE Configuration

Configuration via CLI

Enable PPPoE

Set AC Name

Set MTU/MRU

Set LCP Parameters

Verification

View PPPoE Configuration

View PPPoE Sessions

Check accel-ppp Logs

Integration with RADIUS

Integration with QoS

Validation Rules

Best Practices

Troubleshooting

No PPPoE Sessions Appearing

Sessions Disconnecting Frequently

Sessions Not Getting IP

Next Steps