Internets of Interest for 9th May 2012


Collection of useful, relevant or just fun places on the Internets for 9th May 2012 and a bit commentary about what I’ve found interesting about them:

Avantages of Using SVTI Based VPNs | PacketU – Paul Stewart gives a great example on SVTI. (I”m still learning here).

Starting in version 12.3T (which is some time ago), Cisco started offering an alternative for configuring IOS based VPN’s. This method is called SVTI, or static virtual tunnel interfaces. SVTI is one category of VTI that is basically a configuration alternative for Lan to Lan VPNs. There is also a variant called DVTI, or dynamic virtual tunnel interface, that is a alternative for remote access VPNs.

RFC 1998 Implementation Example: BGP Community Attribute in Multi-home Routing

Taking in consideration that BGP communities are basically prefix tags (oversimplified definition), one can ask how can this be done. I was wondering about it as well, so I have found out that this particular behavior is described in RFC 1998, and it needs to be supported by your ISP. Here is the example:

Great reading.

Just Another Cisco Nexus Install | In Search of Tech – Matthew talks about his recent experiences with the Cisco Nexus:

The most recent Cisco Nexus implementation I was involved in had some challenges. Since you can’t really have an in depth discussion on Twitter due to the 140 character limit, I figured I would throw this post together and share in the fun that is Cisco Nexus switch deployments. Maybe it will help out with someone’s Cisco Nexus implementation. As always, comments are always welcome. Maybe you will see something I missed, or have a question regarding why something was done a certain way.

Importantly, he got answers and solution in the comments. Blog can help you at work.

Fundamental Progress Solving Bufferbloat « jg’s Ramblings

Without an AQM, a  standing queue can be normal result of TCP’s window mechanism, and is not “congestion” as most people have understood it. And since TCP attempts to run a link as fast as it can, any bulk data transfer will cause a modern TCP to open its window continually, and the standing queue grows the longer a connection runs at full bandwidth, continually adding delay unless a AQM is present.  Attacking this standing queue is why an AQM is essential in the Internet; and then TCP can be properly responsive to competing traffic.

Excited about AQM and it’s potential. Not sure that industry acceptance will follow, only time will tell.

IP Traffix Export | CCIE Blog – Initial Draft – Daniel details the IP Traffic Export feature (it’s new to me, time to catch up!!)

With “IP Traffic Export” you can “copy” the traffic that is flowing through an interface and direct it to another device in any of the segments that the router is connected. Every packet that matches the specified export “rule” is going to be sent to a configured MAC address (normally a device in promiscuous mode with a sniffer) outbound on a specific interface in the router. Keep in mind that since the traffic is going to be targeted to the MAC, it needs to be on the same layer 2 segment as the router. Also the outgoing interface can be in production (normal traffic switching), but don’t forget that if the traffic to be exported is too much it may affect the performance of the interface.

Terry Vinson’s CCIE Success Story – Terry Vinsons tells his story of certification success. It certainly sounds like he did it the hard way including paying for it himself while working as an independent contractor, being middle aged and a family man. That’s doing it tough.

Switchport Voice VLAN – What Does It Do? | The Networking Nerd – Core knowledge on VVLANs and switchports. Nicely summarised. (I”d expect no less from Tom)

I hope this was a little more insight into what the magical command switchport voice vlan does on a switch. I’m often asked by people new to voice why this must be configured each time. Before I blindly regurgitated lines like “special 802.1q trunk” and “do it or it won’t work.” Now I have a very interesting story to tell and threaten people with if they don’t do it.

Hacking the 7926G MIDlet Development

My boss came up with the idea of how to use the phones with our current crop of tablets. There will be a barcode on every computer with its’ name. The nurse will scan the barcode of their computer to associate their phone to the computer, then any scanned data will be sent to that associated computer. My boss wrote the listener for the Windows tablets and I wrote the code for the 7926G.

Three part series of blog posts on developing code for CIsco 7920G phones – found it fascinating.

Some Cisco Nexus Design Considerations – Packet Life – Stretch continues to document his experiences :

I’ve been involved with a moderate datacenter deployment of Cisco Nexus switches over the past couple months, and I have learned a good deal about the architecture along the way. Here are some of the design considerations I’ve encountered, and my preferred solution to each.

Service Providers: Open Networking Summit (ONS)… | Brocade Communities – A perspective from Brocade on the ONS 2012.

To wrap up my impression of this summit, I have to say it was great to see so many key industry people in attendance; customers, vendors, implementers and visionaries. I believe that’s one metric that reveals how real SDN is. Not only were there 100s of attendee’s and 10s of booths, but many key influencers in the networking industry were in attendance. Compared to the 1st ONS last year, it was amazing to see the growth in terms of interest and participation, and that the excitement continues to accelerate!

Notably different from Cisco.