[RndTbl] Shaw & dhclient

[Sean Cody]

> From: Trevor Cordes <trevor at tecnopolis.ca>
> Date: November 27, 2006 12:43:54 PM CST (CA)
> To: roundtable at muug.mb.ca
> Subject: [RndTbl] Shaw & dhclient
>
> For a few weeks I've been seeing strange behaviour with dhclient/ 
> dhcp and
> Shaw.  Wondering if anyone else has seen this:
>
> Once a week or so, usually on Sun or Mon, my FC5 box firewall/ 
> router will
> lose its connection to Shaw.  ifconfing will show eth0 up with an IP
> address, but no traffic will come in or out.  Normally, that's a  
> "Shaw is
> down" symptom.  But if I ifdown eth0; ifup eth0, then instantly  
> everything
> is ok again.  And my IP address stays the same.
>
> It's almost like dhclient isn't keeping Shaw's DHCP server happy and
> they're cutting me off until I say, "hey, I'm still here" with a ifup
> kick.

I've been seeing this for MONTHS.

Tried calling support a few times on this with only response of  
'that's weird'.
There was/is signal issues to my apartment complex but that has  
nothing to do with this issue.
There are other people in my office with the exact same issue to  
which the only non-annoying fix was to renew the DHCP lease.

To me it looks like the DHCP lease expires before the expiry date and  
the timing is random though proportional to use.
Mild use, the link drops once every few hours.  Heavy use in an  
interval and it can drop every 5 - 15 minutes.

Either a heartbeat isn't working or the DHCP server is not expiring  
leases properly.
I know (well as much as someone outside the black box can know) it is  
DHCP as once you renew the leases, TCP sessions restore without hang  
up or close states (ie. ssh sessions, ftp transfers).   I see no  
other corruption other than the recently 'standard' latency being  
inversely proportional to upstream throughput. Since shaw is using  
'semi-static' ip leasing this seems the simplest and most logical  
explanation.

You can override in /etc/dhclient.conf but I have no clue if that  
will work.
interface sis0 {
	send dhcp-lease-time 300;
}

What has annoyed me the least was backgrounding the following:
#!/bin/sh
while true; do dhclient sis0; sleep 300; done

You shouldn't have to do either but it has 'fixed' the issue for me.

-- 
Sean
P.S. My kingdom for a decent low latency 5Mb full-duplex line at home  
without the telco line premiums.