The worst feeling for a geek:
Courtesy of xkcd (http://xkcd.com/979/)
This has happened to me twice now: upgrading Mac OS X from one release to another and after the dust settles, the search function in Outlook 2011 totally breaks and always returns “no results”. As we all know, email sucks and being able to deftly search through that mound of crap in your mail client is the only thing that makes it somewhat bearable. Read More >>
Click to enlarge
Here’s the scenario: An enterprise network with an MPLS core and two branch locations connected to their own Provider Edge (PE) router. In addition to the MPLS link, the PEs are also connected via a DMVPN tunnel. The PEs are peering via iBGP (of course) and are also OSPF neighbors on the DMVPN. Both Customer Edge (CE) routers at the branch are OSPF neighbors with their local PE.
Task: Use the high speed MPLS network as the primary path between the CE routers and only use the DMVPN network if the MPLS network becomes unavailable.
Question: Is the solution as simple as adjusting the Admin Distance (AD) so that the iBGP routes are more preferred? Read More >>
In Cisco IOS packets are forwarded through the router (or Layer 3 switch) by Cisco Express Forwarding (CEF). A data structure called the CEF table contains a list of known IP prefixes and the outgoing interface that packets should be put on in order to get them onwards to their destination. That’s well and good. But how do the IP prefixes make it into the CEF table? To answer that question you have to work backwards and understand the order of operations that IOS goes through in order for a prefix to make it into the CEF table. Read More >>
I don’t believe this is well known: Cisco IOS has Role Based Access Control (RBAC) which can be used to create and assign different levels of privileged access to the device. Without RBAC there are two access levels in IOS: a read-only mode with limited access to commands and no ability to modify the running config (also called privilege level 1) and enable mode with full administrative access. There is no middle ground; it’s all or nothing. RBAC allows creation of access levels somewhere between nothing and everything. A common use case is creating a role for the first line NOC analyst which might allow them to view the running config, configure interfaces, and configure named access-lists. Read More >>
If you’ve ever done a traceroute from one IOS box to another, you’ve undoubtedly seen output like this:
R8# traceroute 192.168.100.7
Tracing the route to 192.168.100.7
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.0.1 4 msec 3 msec 4 msec
2 192.168.100.7 4 msec * 0 msec
That “msec * msec” output. Why is the middle packet always lost?? And why only on the last hop?? Read More >>
This is a quick calculator I came up that I could use in the CCIE lab to translate between various IPv4 header QoS markings. As long as I could remember how to draw out the calculator, all I had to do was some basic math and I could translate between markings quite easily. Read More >>
When I started studying in earnest for my CCIE, I started a log of how I was spending my time studying, which books and papers I’d read, videos I’d watched, and so on. I thought it would be a neat exercise to look back afterwards at what it took to achieve this goal. I’m also somewhat self-deprecating and tend to minimize my accomplishments, so having this data is a way for me to remember that this wasn’t a small accomplishment at all.
Read More >>
And now the big reveal. The reason I haven’t been blogging or doing much of anything for some time now is because I’ve had a teeny tiny side project going on:
And this week I passed the lab exam! I am CCIE 47321 (Routing and Switching).
Although I wasn’t actively blogging this year, I’ve still been tracking views on the site and keeping an eye on number of visitors. I am looking forward to blogging again in 2015 so I wanted to collect the 2014 viewership statistics so I had something to compare to at the end of 2015.
Despite the lack of new content, I’m pretty happy that people are reading the existing articles and continue to post comments and email me questions. Please keep them coming!
Read More >>
Dan wrote in with a question:
Hey, I like your site as well… are you going to be doing any more posts? It just seems odd that your last blog post was the analyzation of the site and how it portends to your future work. anyway, good luck
I know it’s tacky to write a blog post about how you’re not writing enough blog posts… but here goes.
Yes, I will be blogging again. And I have lots of content ideas. And I’m actually itching to get back to writing. I’ve been working on something else for the past few months and I decided I couldn’t take that on and blog at the same time. So for now my writing is on hold, however I do see and respond to all comments in the articles and am reachable via email as well.
Thanks to everyone who reads and posts comments. I look forward to writing more posts in the new year!