Broadband Related > FTTC and FTTP Issues
pppoe discovery
bilbokitz:
Is this a particularly sensitive process?
The reason I ask is that I cant seem to get this to work over a vlan, I have a vlan setup due to where my modem and router are located.
If I have my equipment powered down for an extended period of time the router will not connect to the isp, timeout waiting for PADO packets. If I switch the router off for only a minute and back on again it will connect again absolutely fine (presumably as the ppp session is still alive)
When my router wont connect I find that if I move it and connect it directly to my modem it will connect again (most of the time) I can then switch the router off and put it back into its original location which is a bit of a pain. I ran a wire shark and I do see the padi request hitting the modem, it just doesn't get a response from the ISP.
When testing at one point last night I could not get the router to re-connect even when directly connected but for some reason trying a different modem cleared it and it connected, I then reverted immediately to my original setup and all was ok.
Any reason why this process doesn't seem to be occurring over a vlan. The request is untagged when it leaves the modem.
Dray:
I had that working without using a vlan, just plugging in the modem and router into my LAN at different switches.
bilbokitz:
It works fine over the vlan if the ppp session has already been initiated recently, thats the odd thing.
Its an asus router and it has a field for additional pppd options, anything I could try there?
Dray:
Some likely candidates here https://ppp.samba.org/pppd.html
passive perhaps?
WWWombat:
--- Quote from: bilbokitz on December 11, 2017, 11:37:53 AM ---Is this a particularly sensitive process?
--- End quote ---
I wouldn't have thought so.
So long as the switch can cope with the L2 broadcast required for PADI, to flood the packet to all ports in the VLAN.
--- Quote from: bilbokitz on December 11, 2017, 11:37:53 AM ---If I have my equipment powered down for an extended period of time the router will not connect to the isp, timeout waiting for PADO packets.
--- End quote ---
An extended period of time being how long? My initial thought would be how behaviour changes when entries timeout in any ARP caches, or in the MAC table in the switch.
--- Quote from: bilbokitz on December 11, 2017, 11:37:53 AM ---If I switch the router off for only a minute and back on again it will connect again absolutely fine (presumably as the ppp session is still alive)
--- End quote ---
Surely the PPP session won't still be alive if the router has been power cycled. The router must surely go through the whole PPPoE discovery process again, before then starting a new PPP session.
In the end, it looks as though the modem will talk via a switch only if it has recently talked directly to a router. It is almost as though it is "conditioned" to only be able to deal with one partner MAC address... and only communicates with the same MAC as the first talker.
That makes me wonder if, after the router has been turned off for "an extended period of time". the modem learns to talk to the MAC of the switch (eg if the switch talks VTP, DTP, CDP, LLDP or STP) and refuses to talk to any other piece of equipment (ie the modem).
However, when the modem is directly connected, it learns that the "primary partner MAC" is the router. A short power-cycle isn't enough to dislodge "primary partner" status, so the modem then ignores any frames sent by the switch (VTP, DTP etc) but allows fresh PADIs from the router.
In which case... are there some L2 protocols that you need to turn off?
--- Quote from: bilbokitz on December 11, 2017, 11:37:53 AM ---When my router wont connect I find that if I move it and connect it directly to my modem it will connect again (most of the time) I can then switch the router off and put it back into its original location which is a bit of a pain. I ran a wire shark and I do see the padi request hitting the modem, it just doesn't get a response from the ISP.
--- End quote ---
How exactly do you see that the PADI hits the modem?
--- Quote from: bilbokitz on December 11, 2017, 11:37:53 AM ---When testing at one point last night I could not get the router to re-connect even when directly connected but for some reason trying a different modem cleared it and it connected, I then reverted immediately to my original setup and all was ok.
--- End quote ---
Makes me wonder just what kind of MAC caching is going on.
--- Quote from: Dray on December 11, 2017, 11:42:56 AM ---I had that working without using a vlan, just plugging in the modem and router into my LAN at different switches.
--- End quote ---
Dray has a point here. How do the router & modem behave if there is no VLAN, and they are connected into a single plain switch? Or network of switches?
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