Networking

Often this comes into the subnetting discussion by my friends who are deploying IPv6 for the first time. How do you calculate subnets outside the 4-bit nibble boundary? This also happens to be one of starting points of APNIC IPv6 routing workshop where I occasionally instruct as community trainer.

So what is a Nibble boundary?

In IPv6 context, it refers to 4 bit and any change in multiple of 4 bits is easy to calculate. Here’s how: Let’s say we have a allocation: 2001:db8::/32. Now taking slices from this pool within 4 bit boundry is quite easy. /36 slices (1 x 4 bits) 2001:db8:0000::/36 2001:db8:1000::/36 2001:db8:2000::/36 and so on… /40 slices (2 x 4 bits) 2001:db8:0000::/40 2001:db8:0100::/40 2001:db8:0200::/40 /44 slices (3 x 4 bits) 2001:db8:0000::/44 2001:db8:0010::/44 2001:db8:0020::/44 /48 slices (4 x 4 bits) 2001:db8:0000::/48 2001:db8:0001::/48 2001:db8:0002::/48 Clearly, it seems much simple and that is one of the reasons we often strongly recommend subnetting within the nibble boundary and not outside for all practical use cases. However understanding why it’s easy this way, as well as things like how to subnet outside nibble boundary for cases, say if you are running a very large network and have a /29 allocation from RIR.

It has been some time since I started pushing Indian community for hosting RIPE Atlas Probes. These probes are small devices designed to be hosted at end user’s connection and do pre-defined as well as user-defined measurement. Measurement includes ping, trace, DNS lookup, SSL check etc. Currently, there are 61 active RIPE Atlas probes. I would say it has +/- of 7-8 probes which go offline and come back online when I request hosts to check.

I recently came across an excellent draft at IETF by Job Snijders & friends. This is to address scenarios where a network might miss communication about a maintenance activity when BGP shutdown happens. Once implemented, this can potentially offer to send peer a message with up to 128 bytes with info about shutdown like “Ticket XXX: We are upgrading the router, will be back live in 1hr” etc.

It depends by appending such data to the sys notification which is part of BGP protocol. This is one which sends a message just before the shutdown of the session. So it similar to the way you see session tearing down due to prefix limits etc. This has already been implemented in some of the open source routing implementations like OpenBGPd, GoBGP, PMacct, Exabgp etc.   Here is the latest draft of this change.

I posted about the home network in multiple other posts in past. I recent time I switched from Microtik SXT Lite 5 to Power Beam PBE-M5-400. This gave me a jump from 16dbi to 25dbi which gives much sharper beam. I also got a harness & climbed BTS myself (after getting permission from the manager) this time to switch gear. I think I can do a better job than wasting time in finding guys from local WISPs to do it. :)   Also, Essel Group launched Siti broadband in my home area and they are using DOCSIS. The network is overall fine though initially faced many outages due to fibre cuts here & there. As of now, the connection is reasonably stable. I am paying 860Rs/month ~ $14 for 10Mbps uncapped link which gives me 10Mbps down and 1.5Mbps up. From a price point, it’s an excellent connection to have for redundancy reasons. Now as the connection is stable enough to explore auto-failover. For last few months I took both primary links as well as backup links to the router in the form of tagged VLANs and used to push specific traffic based on source IP (device at home) or destination IP/port combination using policy based routing.  

Talking about root DNS server’s anycast at APNIC42. YouTube here.

Saw this excellent presentation in UKNOF 34 by Peter Stevens from Mythic Beasts. Really enjoyed the challenges and fixes he shared in running an IPv6 only web hosting. A must watch for geeks :)  

Also, UKNOF & NLNOG both seem to have excellent content in their conferences along with professional video recording which they make available over YouTube channels.

An impressive and detailed presentation by Mr. Dave Temkin on how Netflix deploys caching nodes and challenges around them. It’s from Feb last year.

One of my friend went for a VM with a German hosting provider. He got single IPv4 (quite common) and a /64 IPv6. Overall /64 per VM/end server used to be ok till few years back but now these days running applications inside LXC containers (OS level virtualization) make more sense. This gives option to maintain separate hosting environment for each application. I personally do that a lot and infect blog which you are reading right now itself is on a LXC container.

RIPE NCC is running an excellent project called RIPE Atlas from few years. This is one of largest distributed network measurement projects where thousands of users host small devices called RIPE Atlas Probes on their networks, home connections, datacenters etc. These probes do measurement under both public and private category and make that data available publicly for use by network engineers and helps in optimizing routing. This page shows detailed coverage statistics of the probes.  

VyOS is quite interesting OS. It’s a open source Linux based network operating system based on Vyatta. It’s config style seems bit like JunOS in terms of hierarchy and set/edit/delete options while editing configuration.  

**Can one use it in a small ISP or a Corporate LAN setup? 

Someone asked me recently if we can have complete open source based router in smaller network doing basic stuff. Not with not-so-streamlined Linux shell but networking OS where network engineers favorite tool “?” works in CLI with options. Let’s take a possible case with bunch of routers, a server with speedtest-mini running on it and end desktop with Ubuntu-desktop on it along with VyOS based router. Goal here is to have basic features to work (to start with!). I am conducting this test and setup on the VM infrastructure at home but that should have zero impact/configuration of network devices and hence not going to focus on that part. All devices including server, desktop and router are pretty much running on virtual machines or KVM containers.     To configure and test: