Optimal PPPoE Settings

Good day all,

I need some assistance with my PPPoE connection. I am not sure that my settings are in line with my ISP. I have been running Ipfire for about 2.5 years. With my upgrade to 2.25(x86_64) core 144, the domain service perpetually broke. The connection was up but no internet traffic could occur due to DNS being broken. The length of time that it took for DNS to break was relatively random.

To get around this problem, I tried several things. 1) I took my DSL modem out of bridge/modem mode and created a double NAT. This works, and I have tested it for about 2 weeks, but is not the ideal situation. 2) My second solution was to turn IPS off on the red side of the network. This also works, and I have tested the connection for about 2 weeks. This would suggest that the IPS/Suricata was not working well with my PPPoE connection. However, I also noted that I had some speed/performance issues. Under solution 1, I had download speed of about 15 Mbits/s and Upload 1.2 Mbits/s. (Yes I am envious of people who complain about their 100+ Mbits/s speeds). However, under solution 2, my speeds dropped to 10.3 Mbits/s Download and Upload of 0.8 Mbits/s. I guess I never noticed the data speed hit associated with running Ipfire as my firewall.

I read the posting at Network Performance Issues on APU4c4 and understand that encapsulation of packets is done on the processor. However, I have run Ipfire on both i3-4005u at 1.7 GHz and a Celeron-3965u processors running at 1.8 GHz. Given that my connection speed is many orders of magnitude smaller than the processor speed I would not expect such a decrease in connection speed. In fact, if I was running up against processor performance, I would not expect my “Idle CPU Usage” to be reported as on average about 96%.

So that got me looking around in the system. Looking at /var/ipfire/ppp/settings, I could not help but notice that some of the setting were not correct. For instance the VPI/VCI was set to 1/32, but my ISP requires a VPI/VCI of 0/32. As the wiki page https://wiki.ipfire.org/installation/red says, some ISPs might need some fine tuning. I figure that the script that writes out the setting file found a solution that works, but it is not the best solution. I assume that if I manually change /var/ipfire/ppp/settings I can potentially find a better set of settings. Is there a reference or some other documentation as to the various parameters? In looking at the file, I can somewhat decode it, but what are acceptable values for:

USEDOV
MODEM
PROTOCOL
ENCAP
DTERATE
MODULATION
COMPORT
ATM_DEV
USEIBOD
LINE

I have figured out what parameters my ISP wants, I believe I just need to match them. I really appreciate any help that can be given.

This parameters are not used if you use PPPoE via a normal Ethernet Cabled modem.
VCI/VPI is a modem internal setting. If you have an external modem you need to configure this in the modem.

if an Internal ATM Modem is installed in the IPFire and you have selected PPPoE over ATM. In this case you can configure this parameters VCI, VPI ENCAP, PROTOCOL, ATM_DEV normal via the GUI. (VCI/VPI was set to 1/32 because the most german ISP’s has used this)

other parameters (DTERATE, COMPORT) are only for modem connections and some are legacy for PPPoA or PPPtP

so usually none of this parameters need manual tuning.

Thank you for the information, it was extremely helpful. It pointed me to the solution. The problem is definitely not a IPFire issue, it appears that my modem is either bad or not doing what I expect in bridge mode. Changed out the modem for an old one and everything works as expected.