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Excerpt: This started off as a company email but I wanted to share it, since I’ve been asked before. Below is opinion and opinion only. I’m more interested in how this compares with your study methods and Cisco exam experiences, so please let me know your thoughts in the comments. Cisco exams….let’s face it, they suck. (In a good way though) I’ve taken exams from all kinds of vendors, and Cisco is *really* good at creating exams that vet you technically, but also require that you understand the practical reasons for the technologies we work with, not just memorizing maximum values, or…
KIClet: Cisco UCS vHBA Template Bug
January 24, 2012 by 1 Comment
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Excerpt: I found a bug in the vHBA Template creation screen on Cisco UCS 2.0. It’s not too bad, but still a little annoying, and can cause you to have some problems depending on how you have your VSANs set up. If you notice, the default VSAN is selected for my vHBA template. I have named my VSANs “fabric-a” and “fabric-b”. If I drop down the VSAN selector, I have the ability to select the VSAN I have associated with fabric A: However, once I’ve done so, and I change to fabric B, I drop down the selector again, and I now am able…
Virtual Switching System (VSS) on Cisco Catalyst 6500
October 5, 2011 by 7 Comments
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Excerpt: I’m currently working on a project that, among other things, involves the installation of two Catalyst 6509 switches. I was recently shown a redundancy feature that I had never heard of before called Virtual Switching System (VSS). The more I looked at it, the cooler it was. The main reason for VSS is something that is typically addressed when there are redundant routing platforms on a network. There are actually quite a few solutions that can be used in the presence of redundant devices, such as the popular and Cisco-proprietary Hot Standby Router Protocol (HSRP), or the IETF open standard Virtual…
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…
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…
Configuring OSPF Between Vyatta and Cisco IOS
September 8, 2011 by Leave a Comment
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Excerpt: This is a guide to configuring OSPF between Cisco IOS and the open-source Vyatta router platform. I was able to do all of this on my desktop PC, by running Cisco IOS in GNS3 and Vyatta as a virtual machine. I used the guide here to bridge both virtual routers together, so that communication could be established. The Cisco side was pretty straightforward. I configured the FastEthernet interface and enabled OSPF on it: R1#(config)interface Fa0/0 R1#(config-int)ip addr 172.16.0.1 255.255.255.0 R1#(config-int)no shut R1#(config-int)exit R1#(config)router ospf 1 R1#(config-router)router-id 1.1.1.1 R1#(config-router)network 172.16.0.1 0.0.0.0 area 0 The Vyatta side took some doing, though there were more interfaces involved here, so that could be…
