I created two new twitter accounts yesterday and the amount of followers in such a short time is great to see. Feel free to follow them here – @bgp4_table and @bgp6_table The accounts get updated through Python, and that Python script is run via a cron job once every six hours. I noticed that when I ran my script manually, it worked fine. When the cronjob ran it, nothing happened. As there is no console log it made me wonder what the issue was. ...
For an electronics project I’m working on I wanted a way to check the current global routing table every five minutes for both IPv4 and IPv6. I did not want to log into anyone else’s router or looking glass as checking every 5 minutes may be considered abuse. So I thought to spin up a bird routing instance. I just wanted to receive the routes, not actually install them into the kernel on my linux box. From there I’d be able to check the table size sent over. ...
At the end of my last post on Python multithreading, I said my example was not the best. Let me expand some more on this. While testing code in the previous post, I noticed that certain code was slower when multiple threads were running. Also these threads are not tied to a CPU. If we were talking about a bigger applications in which we wanted to ensure multiple threads were on different CPUs, you are in fact looking for multiprocessing. ...
The first ‘proper’ Python app I made logged onto a list of devices and pulled out OSPF state. This worked perfectly fine. The app correctly works out whether it can log into a device or not, and waits a few seconds to ensure a device actually responds. The issue is that if I have a list of say 1000 devices, and 500 of them don’t respond, the amount of time you need to wait rapidly increases as it looks at each one in turn. Would it not be better for the app to be able to log into multiple devices at the same time in parallel? This would drastically reduce the runtime. ...
I had a specific requirement recently and I wanted to test it’s behaviour. In particular the feature is DHCP snooping. Let’s quickly go over the DHCP process at a high level to see how it works: DHCP Let’s take the following simple diagram to show what’s going on. We have a switch with two hosts connected. We also have a DHCP server. I’m using generic names as I’ll be testing this on different switches. Assume all devices are in the same vlan. ...
I usually have access to an ESX box at work where I can run multiple VMs and virtual routers for labbing and testing. I’ve also wanted one at home. It’s nice to be able to quickly spin up VMs when needed without always running them through my laptop. While virtual routers don’t need lots of resources, I did want a beefy machine as there are a few servers I’d like to get running that need lots of CPU power. ...
I’ve just started with object oriented programming in Python so I thought I’d cover some of the basics here. Please don’t assume this is a thorough tutorial on OOP! The beauty of OOP is that it allows me to create a template with which I can create objects. The building blocks of the object sit in the class, while the object itself is created from that blueprint with various properties. I can then make as many of these objects as I desire from that single class. I can see this being very beneficial for certain types of programming (games especially) ...
I was forced to use a 3750G as a router yesterday for a WAN link that was only 70Mb. The LAN interfaces were all gig. The customer wanted to ensure that 30% of the bandwidth was available for EF marked packets. Everything else was to get 70% A lot of people have trouble with QoS on the 3750. This is mainly due to the tiny buffers, complexity, and the defaults it uses. ...
An ethernet physical port can only run at certain speeds. i.e. 10/100/1Gb/etc – Often customer will purchase a sublevel of bandwidth on that bearer speed. For example Customer A wants to buy 30Mb of bandwidth. You can’t run the physicla ports at 30Mb, so the ISP will have the interface run at 100Mb and police inbound at 30Mb. This makes QoS jus a little more complicated. All the ratios we’ve used in the past will ratio themselves at the WAN port’s physical speed. Also the router will not know that if 40Mb of burst comes from the LAN, that the actual bandwidth is only 30Mb. ...
Going back to the diagram we used in part 1. Let’s say that we want to shape certain traffic to certain bandwidths under congestion. I want EF packets to get 20Mb priority, AF31 packets to get 50Mb and whatever is left to get 30Mb. I want to enable WRED in the BE queue, and also modify the default WRED profile. I’m going to take the assumption that packets have already been marked correctly as shown in my first post. ...