[RP-PPPoE] rp-pppoe and vlans

[Insane Laughing Clown]

On 09/27/2012 05:23 AM, Tiago wrote:
> Hello all,
> How are you doing vlans with pppoe-server? Which kind of configs are
> necessary? How do you allocate IPs? Using freeradius ? or using
> ip-pool file?

VLANS are just another interface for pppoe-server to listen on and serve 
requests on. It doesn't have sophisticated per-interface configuration 
rules or anything like that, so depending on how specfic you need to be, 
you may have to run multiple instances of the server.

VLANS are configured in the operating system, pppoe-server has no 
awareness of them. Typically under linux you would use the vconfig tool 
to do so.

>
> Are you using public IPs for pppoe-interfaces or private IPs? How do
> you use pppoe-server command line to start this scenario?
>


The server side ip assigned to the point-to-point interface only shows 
up in the customer router as a /32, at best. In practice, you likely 
could use a single ip like the default '10.0.0.1' without causing any 
issues. Correctness, in my opinion however, would be to have the server 
use it's loopback address (if you have one assigned for dynamic routing 
purposes; I am not talking about 127.0.0.1, but rather a /32 usually 
given to the 'loopback' interface which identifies the box in the 
hierarachy of dynamic routing gateways, assuming you are doing so). Or, 
any other public address you have reserved for the box. By using a 
public address, you are ensuring uniqueness in that you are not putting 
a conflicting, duplicate or overlapping address in the customers routing 
table.

pppoe-server -I vlanX -I vlanY -I vlanZ -L my.public.ip.address .... 
other options go here...



> How many customers per vlan are you using? How is the impact on the
> network (loops, broadcasts, etc...) in your experience?
>
There's lots of issues to think about here.

Using vlans allows you to segment your network. Depending on the type of 
network you have - eg: wireless, dsl, or what have you - there are 
various advantages you can gain and various scaling issues you may face.

I would certainly reccomend using vlans to group customers together, say 
by pop or 'proximity' to the server. Another use is to take advantage of 
multiple cores in your server box by using vlans and having seperate 
instances of pppoe-server running and listening on those interfaces. 
pppoe-server doesn't use hash tables internally and instead uses linear 
list lookups, so some control protocol functions can case the server to 
expend significant time looking up the 'right' ppp instance to associate 
the control packet with. These are things like padt for example. Since 
pppd is a seperate process per user it won't help with individual 
connections, but rather just having multiple server instances helps with 
overall scale.


I have run about 1000 subscribers on a vlan and while 'it works', better 
network design on my part would have reduced this. I think in my case 
judicious use of a pppoe-relay in some parts of the network would have 
had good effect.

> Thanks very much!
>

-ILC