Subject: PPPoE + fragmentation + bad hdr length
To: None <>
From: Dan Fraser <>
List: tech-net
Date: 10/04/2004 16:33:30
I've suddenly started to have problems talking between my two netbsd
boxes.  One of them is running 1.5.x and is hosted at a colocation
facility.  My home computer is running NetBSD 1.6.x and is hosted on a
PPPoE DSL link.

Small packet communication is fine (interactive ssh) but as soon as larger
packets are sent, the link pretty much freezes.

tcpdump shows things like this (miso is on the real link):

16:31:19.533221 PPPoE  [ses 0x618] > . [bad hdr length] (frag 2000:24@0+) [tos

16:32:24.021644 PPPoE  [ses 0x618] > . [bad hdr length] (frag 2187:24@0+)

Both machines have no trouble communicating with other sites.

How can I troubleshoot this?

Dan J. Fraser <>
PGP: 0xF3972A01 (17 B7 24 90 27 05 B8 92  4F 7F 61 18 B9 D1 17 CE)
"Verbing weirds language." -- Calvin