Bug #260

WAN port won't DHCP successfully (it would not receive packets, but would transmit them)

Added by Jim Gettys on Sep 1, 2011. Updated on Apr 21, 2012.
Closed High David Taht

Description

In smoketest 4 of RC6, the WAN port would not DHCP on my local network; which is a bit of a mess.

It was plugged into a DLINK DGS-2208 Gigabit switch, which is plugged into a 100Mbit switch, which is plugged into a WNDR3700v2 (running the Bismark build).

Hypothesis: it might have problems if it sees ethernet pause frames. I first became aware of pause frames when I saw them in a wireshark capture I took off this switch last fall.

My laptops dhcp off this switch just fine, FWIW.

History

Updated by Jim Gettys on Sep 20, 2011.
This problem appears to be present still in real RC6. Plugged directly into the router serving as my home router, it dhcp’s on the wan port fine and works.
Updated by Dave Täht on Sep 20, 2011.
We need to find a way to reproduce this in front of a developer that has this switch AND problem.

I was unable to reproduce in a similar environment.

Updated by Jim Gettys on Sep 20, 2011.
OK, I’ll get a new switch ordered so that I can take the existing one that seems to trigger it out of service (mercifully), and we can reproduce it in front of someone able to debug it.
Updated by Jim Gettys on Sep 20, 2011.
Weirder and weirder. I thought that the switch in question was a 100Mbit switch; instead, it’s a netgear 108p (8 port 10/100/1000Mbit POE switch). Additionally, I have another level of switching beyond this (a d-Link 2208). So I need to do a bit more debugging, and plug the router one step back (directly into the netgear) first to confirm at what level the problem is.
Updated by Dave Täht on Sep 20, 2011.
I’ll argue it’s at the number of levels it’s at… rule of thumb: never connect more than 3 switches together.
Updated by Jim Gettys on Sep 20, 2011.
Yeah, but the factory firmware coped ok, when I tried it before.

I’ll do a more systematic round of tests in the morning.

Updated by Dave Täht on Apr 21, 2012.
so far as I know this hasn’t been a problem in months.

This is a static export of the original bufferbloat.net issue database. As such, no further commenting is possible; the information is solely here for archival purposes.

Cerowrt Project

News items
List of Wiki pages
List of bugs
RSS feed

Recent Updates

Jul 21, 2024 Wiki page
cake-autorate
Jul 21, 2024 Wiki page
What Can I Do About Bufferbloat?
Jul 21, 2024 Wiki page
Tests for Bufferbloat
Jul 1, 2024 Wiki page
RRUL Chart Explanation
Dec 3, 2022 Wiki page
Codel Wiki

Find us elsewhere

Bufferbloat Mailing Lists
#bufferbloat on Twitter
Google+ group
Archived Bufferbloat pages from the Wayback Machine

Sponsors

Comcast Research Innovation Fund
Nlnet Foundation
Shuttleworth Foundation
GoFundMe

Bufferbloat Related Projects

OpenWrt Project
Congestion Control Blog
Flent Network Test Suite
Sqm-Scripts
The Cake shaper
AQMs in BSD
IETF AQM WG
CeroWrt (where it all started)

Network Performance Related Resources


Jim Gettys' Blog - The chairman of the Fjord
Toke's Blog - Karlstad University's work on bloat
Voip Users Conference - Weekly Videoconference mostly about voip
Candelatech - A wifi testing company that "gets it".