home | list info | list archive | date index | thread index

[OCLUG-Tech] Re: [oclug] dhcp grief

On Sun, Mar 06, 2005 at 11:31:16AM -0500, Mike wrote:

> Well I thought I had isolated my troubles. But no such luck.  I
> wrote a little script to track my IP, when things were bad the IP
> was changing every 10 minutes (the time of the cron job).

Note that there are also far better ways to track IP than by cronjob,
and more efficient to boot.  See the bottom of the message for details
because I don't think it's part of your main problem.

> After trying to tweek dhcp and  the pppoe configurations on my SuSE 9.0
> machine 

Wait a sec.  Which one are you using, DHCP or PPPoE?  What provider
are you using?  I don't know of any that use both simultaneously.

If you're using them both, they could very well be conflicting.  I'd be
surprised if you got a DHCP lease at all.

Bear in mind that even getting a DHCP lease may not mean you're
connected to anything.  If I unplug my cable modem from the wall,
it starts handing out leases in the private IP range (192.168.*).
This allows me to access the modem's internal webserver to check
its status.

> This fits in with the earlier observation of being able to ping a
> site but not load the page.

Perhaps, although this is most commonly a too-high-MTU symptom.

Note that setting the MTU isn't enough.  You should set the TCP MSS as
well.  See a previous message I wrote this week on that subject.

> The online DSL speed tests say things are OK, but after hitting the back 
> button it reports I have a T3.

Sounds like something got cached.

Anyway, tracking your IP without cron:

For PPPoE, since you're using the PPP daemon, you'll probably
find some directories in /etc/ppp that can contain scripts to run when
PPP comes up or when it goes down.

Mine's located at /etc/ppp/ip-up.d.  In this directory, if I put
an executable script there, it'll be run every time the PPP
link comes up.

If your distro doesn't have that, you can put your commands in
/etc/ppp/ip-up, which (at least in my distro) is called when
PPP comes up.  Check the manpage for pppd.

Note that the better DHCP clients have a similar system for when they
acquire leases.

Attachment: signature.asc
Description: Digital signature