Blog Posts in April 2017
Ansible, Puppet, Chef, Git, GitLab… the list of tools you can supposedly use to automate your network is endless, and there’s a new kid on the block every few months.
In Episode 77 of Software Gone Wild we explored Salt, its internal architecture, and how you can use it with Mircea Ulinic, a happy Salt user/contributor working for Cloudflare, and Seth House, developer @ SaltStack, the company behind Salt.
Jordan Martin published a nice summary of what I’ve been preaching for years: centralized control plane doesn’t work (well) while controller-based network orchestration makes perfect sense.
While I totally agree with what he wrote he got the hype angle wrong:
Short update for those that read the original blog post: it turns out that the answer to the question “Is it possible to run VMware NSX on redundantly-connected hosts in a pure L3 data center fabric?” is still NO.
VTEPs from different ESXi hosts can be in different subnets, but while a single ESXi host might have multiple VTEPs, the only supported way to use them is to put them in the same subnet. I removed the original blog post.
A huge thank you to everyone who pushed me with their comments and emails to find the correct answer.
I’ll be doing several on-site workshops in the next two months. Here’s a brief summary of where you could meet me in person.
A bit of manual geolocation first: if you’re from Europe, check out the first few entries, if you’re from US, there’s important information for you at the bottom, and if you don’t want to travel Europe or US, there’s an online course starting in September ;)
One of the toughest challenges you can face as a networking engineer is trying to understand what the customer really needs (as opposed to what they think they’re telling you they want).
For example, the server team comes to you saying “we need 5 VLANs between these 3 data centers”. What do you do?
Here’s an interesting blog post (particularly as it’s coming from a well-known cloud evangelist): at the infrastructure level stability matters more than agility or speed-of-deployment. Welcome to real world ;)
During Cisco Live Europe 2017 (where I got thanks to the Tech Field Day crew kindly inviting me) I had a nice chat with Peter Jones, principal engineer @ Cisco Systems. We started with a totally tangential discussion on why startups fail, and quickly got back to flexible hardware and why one would want to have it in a switch.
I recently finished editing the videos from the Leaf-and-Spine Designs update to the Leaf-and-Spine Fabrics webinar, so it wasn’t hard to select the featured webinar for April 2017. The featured videos now include BGP in the Data Center by Dinesh Dutt, SPB Deep Dive by Roger Lapuh, and VXLAN with EVPN control plane by Lukas Krattiger.
One of my readers considered joining the Building Network Automation Solutions course but wasn’t sure whether it would help him solve the challenges he’s facing in his network.
Fortunately, his challenges aren’t that hard to solve.
Evgeny made an interesting observation while testing the NETCONF client on IOS XE 16.x (see also this comment on my blog):
The most interesting part: for unknown reason IOS-XE gives different answers about capabilities on ports 830 and 22.
In case you’re wondering why we’re stuck with old stuff like TCP, IPv4, OSPF, and a few other bits and pieces that were invented decades ago when we could be using the glitzy controller-based software-defined whatever, read the blog post by Martin Sustrik. He talks about software, but we’re facing the same challenges in networking.
Lukas Krattiger (Cisco Systems) was the guest speaker in Layer-2+3 fabrics part of the Leaf-and-Spine Fabric Design webinar, and he started his presentation with an overview of how we use overlays in data center fabrics.
Most network automation presentations you can find on the Internet focus on configuration management, either to provision new boxes, or to provision new services, so it’s easy to assume that network automation is really a fancy new term for consistent device configuration management.
However, as I explained in the Network Automation 101 webinar, there’s so much more you can do and today I’d like to share a real-life example from Jaakko Rautanen, an alumni of my Building Network Automation Solutions online course.
Johannes Weber built a CCNP practice lab, configured 22 different protocols in it, and took packet captures of all of them happily chatting. To make things more interesting he created 45 challenges that you can solve with Wireshark using the pcap file he published.
One of my readers sent me a link to CCO documentation containing (at that time) this gem:
Beginning with Cisco NX-OS Release 7.0(3)I2(1), Cisco Nexus 9000 Series switches handle the CLI configuration actions in a different way than before the introduction of NX-API and DME. The NX-API and DME architecture introduces a delay in the communication between Cisco Nexus 9000 Series switches and the end host terminal sessions, for example SSH terminal sessions.
So far so good. We can probably tolerate some delay. However, the next sentence is a killer…
2017-04-05: The wonderful information disappeared from Cisco's documentation within 24 hours with no explanation whatsoever. However, I expected that and took a snapshot of that page before publishing the blog post ;)
My Why Do We Need Session Stickiness in Load Balancing blog post generated numerous interesting comments and questions, so I decided to repost them and provide slightly longer answers to some of the questions.
Warning: long wall of text ahead.