networking network_error ai_generated partial

PPPoE: PADI timeout, no Access Concentrator responded on interface eth0

ID: networking/pppoe-padi-timeout

Also available as: JSON · Markdown · 中文
80%Fix Rate
86%Confidence
1Evidence
2024-01-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
rp-pppoe 3.15 active — — —
Linux kernel 5.10 active — — —
OpenWrt 22.03 active — — —

Root Cause

The PPPoE client sent a PPPoE Active Discovery Initiation (PADI) broadcast but received no PADO response from any Access Concentrator, indicating no PPPoE server on the network or a layer-2 issue.

generic

中文

PPPoE客户端发送了PPPoE主动发现初始化（PADI）广播，但未收到任何接入集中器的PADO响应，表明网络上没有PPPoE服务器或存在二层问题。

Official Documentation

https://datatracker.ietf.org/doc/html/rfc2516

Workarounds

  1. 85% success Check if the interface is connected to the correct VLAN: ip link show eth0 ; verify VLAN tagging matches the ISP requirement, e.g., vconfig add eth0 10 ; pppoe -I eth0.10 
    Check if the interface is connected to the correct VLAN: ip link show eth0 ; verify VLAN tagging matches the ISP requirement, e.g., vconfig add eth0 10 ; pppoe -I eth0.10
  2. 80% success Run tcpdump to confirm no PADO is received: tcpdump -i eth0 -e -n 'ether proto 0x8863' ; if no packets, contact ISP or check physical connection 
    Run tcpdump to confirm no PADO is received: tcpdump -i eth0 -e -n 'ether proto 0x8863' ; if no packets, contact ISP or check physical connection

中文步骤

  1. Check if the interface is connected to the correct VLAN: ip link show eth0 ; verify VLAN tagging matches the ISP requirement, e.g., vconfig add eth0 10 ; pppoe -I eth0.10
  2. Run tcpdump to confirm no PADO is received: tcpdump -i eth0 -e -n 'ether proto 0x8863' ; if no packets, contact ISP or check physical connection

Dead Ends

Common approaches that don't work:

  1. 90% fail

    If no AC exists, retrying the same broadcast will still time out; the network must have a PPPoE server.

  2. 65% fail

    PADI is a broadcast and typically not blocked; the issue is usually at the server side or VLAN mismatch.