PPP LCP Keepalives & Troubleshooting it on Junos

Until the last week I had quite vague understanding of how LCP keepalives work - it was just one of those underlying protocols you have general knowledge about but never really go in details with. However, last week I encountered a problem that required slightly deeper understanding of how it works, and since some of the important details are not emphasized in the sources I read, I decided to write a short note on this topic.

So, how does it work? Let's take a look on a capture taken between a PPPoE server and a Linux client:

IPv6 Free Core: Configuring IPv6 Labeled Unicast on Juniper MX

Here's just a short note on IPv6 Labeled Unicast - an elegant solution to the case where you need to connect two IPv6 sites through your IPv4-only network. (The other option would, of course, be to enable IPv6 on all of your core routers, which is not always convenient).

So here I'm going to show you the minimal configuration to get this lab up and running, a trick that would make the configuration more optimal and elegant (why would you need "explicit-null"?), and take a quick look on what's going on behind the scene.

That's what my topology looks like:

Configuring CoA: Juniper MX + FreeRADIUS

Recently I had to configure CoA on Juniper and was surprised by how vague the coverage of this topic is. Juniper's Day One on CoA is not bad, however, in my opinion, sometimes it's focusing on unnecessary details while missing the important ones.

As you probably already know, CoA, or Change of Authorization allows you to modify subscribers sessions "on the flight", without having to disrupt the session. CoA is usually used together with some kind of billing software, so you can implement all kinds of things - for example, implement time-scheduled rate-limiting (imagine, for example, that you as ISP provide a tariff that allows unlimited speed at particular hours and lower speeds at all other time), or abrupting internet access as soon as there's no money left on client's account...and so on.


My topology is as simple as possible and looks like this: