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Excerpt: I woke up this morning and realized that I had broken my 3-week long streak of blog posting, where I had gotten in the habit of making a new post nearly every day of the week. Since I have been unemployed for the past three weeks and my primary priority was to study for the CCNP, it was easy to come up with new blog content at a relatively rapid pace. I have recently taken a position with a Cisco partner that allows me to work with a lot of new Cisco gear, as well as replacing or integrating with other…
Where Did All The Time Go?!?
September 29, 2011 by Leave a Comment
BGP: Weight and Local-Preference
September 25, 2011 by 2 Comments
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Excerpt: It’s important to remember that since BGP is the routing protocol of the internet, there are quite a few attributes that it uses to give preference to a single route out of several redundant paths to a given destination. I was recently contemplating several of these and it occurred to me that two of these attributes in particular are pretty similar. I’d like to compare and contrast them and give reasoning for situations that call upon one or the other. I’ll be referring to this diagram throughout the article, use it for reference. We’ll be trying to use weight and local preference…
EIGRP Unequal-Cost Load-Balancing
September 22, 2011 by Leave a Comment
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Excerpt: In a previous post, I explored the basics of IP routing, and in the process, we discovered an interesting default feature of OSPF. When there were two OSPF routes in the routing table to a network, and both routes had the same cost, the router performed load balancing between the two. Take, for instance, the following route: 172.16.2.0 [110/12] via 1.1.1.13, 00:09:24, FastEthernet0/0 [110/12] via 1.1.1.2, 00:09:24, FastEthernet0/1 In this example, every packet sent would take one of two routes. The next hop at this particular…
Changing Gears: Virtual Networking
September 21, 2011 by Leave a Comment
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Excerpt: When it came to networking, my university classes didn’t teach me much more than the basics of network infrastructure, and a little bit of route/switch. Now that I’ve graduated, I continue to learn as I strive for the next steps. So far, it’s been CCNP ROUTE, since I knew I wanted to go for it soon after CCNA. Because of this trend, I’ve been pretty devoted to routing, with a small segway into security as I obtained my Security+ certification. With all of that going on, I’ve had little time to look into what I’m sure will become a big…
Review: Ethernet Fabric Whitepaper by Brocade
September 20, 2011 by Leave a Comment
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Excerpt: I’ve been pretty deep into my CCNP ROUTE studies, which is mostly WAN and routing protocols, so I haven’t had much chance to dive any deeper when it comes to datacenter stuff. I’d seen several ads for the Brocade whitepaper titled “Five Reasons Classic Ethernet Switches Won’t Support the Cloud” and I figured I’d give it a shot. The whitepaper is not long, and is quite easy to understand. It contrasted well between traditional switches and Ethernet Fabric switches in terms of supporting SaaS application requirements, pointing out that while STP is a necessary evil in a classic Ethernet switched infrastructure,…
EIGRP over NBMA Networks
September 19, 2011 by 4 Comments
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Excerpt: Commonly used routing protocols like OSPF and EIGRP utilize multicast addresses to distribute hello messages, and routing information. In a broadcast-capable layer 2 network like Ethernet, EIGRP will send a packet containing a hello message to the address 224.0.0.10, which results in a corresponding layer2 destination 01:00:5e:00:00:0a. Something I used to wonder about all the time is how routing protocols work over Non-Broadcast Multi-Access networks like Frame Relay. In these networks, there are no broadcasts or multicasts. With Frame Relay, a service provider will set up PVCs for an organization which act like virtual layer 2 point-to-point connections. Each PVC will…
Vyatta OSPF Designated Router Concepts
September 16, 2011 by Leave a Comment
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Excerpt: I was inspired by a (relatively) recent post by Jeremy Stretch at Packetlife.net that explained OSPF designated router configuration in Cisco IOS. I’d like to go into a bit more detail regarding the need for a designated router, and explore the same configuration steps on the Vyatta Core platform. I’ve already shown how easy it is to integrate a Cisco router with a Vyatta router using OSPF, so you can use a mix of Cisco and Vyatta gear if you wish. To understand the purpose of a Designated Router in OSPF, you need to know how OSPF distributes routing information around the…
