What Are Your Challenges?

In IT, we are always surrounded by challenging tasks. Whether it is troubleshooting a routing issue, fixing an outage or planning a new wireless deployment we run into many challenges.

Here is my question to you:

What is your biggest challenge right now?

Let me know in the comments below.

My current challenge is balancing work with an MPLS and QoS design with CCNP ROUTE studies and family. Somewhere in between all of that I try to sleep ;)

What is the big item on your plate?

Book Review: CCNP SWITCH 300-115 Official Cert Guide

Book Review: CCNP SWITCH 300-115There are only a handful of books to select from when studying for the CCNP SWITCH 300-115 exam. It’s tough to make the right decision on a resource for an exam that costs $250 to sit in. My go-to book resource is Cisco Press. In short, I passed the CCNP SWITCH (300-115) exam on January 20th, 2015 with the assistance of CCNP SWITCH 300-115 Official Cert Guide.

When I started studying for this exam on October 31st, 2014, there wasn’t a book available covering the new objectives. I printed the exam objectives and started reading configuration guides. As soon as the books were available, I put an order in with Cisco Press and I was off.

The author, David Hucaby, did a great job with his explanations. The book itself isn’t as big as ROUTE. What I like about this book is it is easy to follow along with Cisco’s objectives. After passing the exam, I can say that it covers it very well. David helped me to understand topics where I was weak. It helped reinforce the fundamentals of Spanning Tree and redundancy such as GLBP.

Within the book are good diagrams and configuration examples. The little details are in there as well such as timers, intervals, etc. You’ll need to remember those for the exam.

In preparation for the exam, each chapter is preluded with a chapter quiz. I used those pre-chapter quizzes after I have read through the entire book. The questions are very good compared to the exam. I dig deeper into other topics where I score lower than 80%. Each chapter has anywhere from 10-15 questions so it’s not something to rely on.Continue Reading…

Windows Server NLB VIP Multicast Mode Through Cisco Switch

If you are unable to connect to a Windows Server Network Load Balancing (NLB) Virtual IP address configured for Multicast Mode it is because of the way your Cisco switch interacts with Microsoft NLB.

Symptoms

  • Cannot connect to Windows Server NLB Virtual IP address
  • Cannot ping Windows Server NLB Virtual IP address
  • Microsoft NLB Multicast Mode not working

I won’t go into the details of how NLB works but in short, client requests are distributed across different servers. To configure NLB, you can use three modes:

  • Unicast
  • Multicast
  • IGMP

Using Multicast Mode

When using Multicast mode, the cluster members will respond to ARPs using their virtual IP address and a multicast MAC address. Without the proper configuration on the switch you will not be able to connect to the Virtual IP address.

This will not work because within the ARP request packet is a unicast IP address and a multicast MAC address. Troubleshooting it can be frustrating but a Cisco switch will ignore this. Below is the configuration to be done on the switch.

Cisco Switch Configuration

To resolve the problem, create a static ARP entry for the Virtual IP Address to the NLB MAC address. Then create a static MAC address entry to the VLAN and interfaces used by the cluster.

In my case, my virtual IP address is 192.168.10.10 with MAC address of 03bf.0a65.05fa. That IP address is on VLAN 10 and the servers’ interfaces are part of a port-channel, both Port-Channel1 and Port-Channel2.

The following configuration is as follows:

arp 192.168.10.10 03bf.0a65.05fa
mac address-table static 03bf.0a65.05fa vlan 10 interface Port-Channel1 Port-Channel2

Some configuration items to note.. not all Cisco switches will support a static entry of a MAC address to multiple interfaces. In my case I am using a Cisco Catalyst 4500-X in VSS mode. The servers had two network interfaces configured into an EtherChannel.