[oclug] rp-pppoe and static dhcp assignments

[Bob Lockie]

On 06/02/04 10:40 todd.clattenburg at sdc-dsc.gc.ca spoke:
> Hello
> 
> I have a question about rp-pppoe and dhcp IP assignments. I will try
> and be as complete, and as concise as possible.
> 
> I have subscribed to a 'static IP' plan from my ISP. I have a server
> running fedora, rp-pppoe, and a number of other services which I
> access via my static IP over the internet. After a recent reboot I
> was issued the wrong IP (not my assigned static IP). I called up my
> ISP to complain, and they explained to me that my connection was
> re-connected too quickly so their (dhcp servers/access concentrator)
> did not have enough time to determine the connection was down, and
> re-issue the same IP. Their server thought that my static IP was
> still in use, so it issued a different one. I browsed through the
> dhcp rfc (rfc1541 section 3.2) and this does not seem to me to be the
> proper behavior for a dhcp server dealing with a request for a
> statically assigned IP. I understand that pppoe may require or result
> in some different behavior for dhcp requests, that is kind of what I
> wanted independently verified here.
> 
> The ISP told me that I would need to set up a 60-90 second pause in
> my server to prevent my server from attempting requesting a session
> twice within that period. So that their servers/access concentrator
> had a chance to flush their current registered sessions. I asked them
> if I should be able to reliably reproduce this behavior and they said
> that it would only occur when their servers are experiencing heavy
> loads. They also indicated that they have no intention of changing
> their servers any time in the near future to remedy this latency
> despite the fact that they offer a 'static IP' package. They said
> that I would need to reconfigure my server to verify that I have
> received my static IP if I wanted to be sure that I received it.

I am very skeptical.
Get a competent ISP. :-)


> Can I set this delay up somehow with rp-pppoe?
> 
> Also, since PPPoE is session-based how often does it re-initiate a
> session if the connection is idle? or, how long does the connection
> need to be idle to have the session expire?
> 
> I was thinking of just writing a perl-script for the cron tab and
> having it check the IP, and if it is not my static IP then pause 90
> seconds, kill, and restart the DSL session. But how often would this
> have to run, or could I change the adsl-start command to validate the
> IP received, and if it was the wrong one, wait 90 seconds, and kill,
> reconnect. hmmm. Just typing the this letter is giving me ideas.

The ADSL start command is just a script.
Any changes will be lost if you upgrade. :-(

Run the crontab script as often as you'd be willing to have the wrong IP.
The best idea would be to integrate it with rp-pppoe.
I couldn't


> I would like to know if anyone else is experiencing or has
> experienced similar problems, and if y'all know of a cleaner
> solution.
> 
> Any insights or ideas would be appreciated.

I have no idea what this parameter does but it looks promising:

man dhcpcd
        -s [ipaddr]
               Sends  DHCP_INFORM  message  to  DHCP  server using 
ipaddr.  The optional ipaddr parameter must be in the  form 
xxx.xxx.xxx.xxx. If  no ipaddr parameter is given on the command line 
dhcpcd will use the IP address currently  assigned  to  the  interface. 
   If there  is  no  IP  address  currently  assigned to the interface 
          dhcpcd  will  use  previously  obtained  IP  address  stored 
in              /var/cache/dhcpcd-<interface>.cache file.