I tackled the original Switching exam 640-504 in November 2001. This refresh of that test includes all the latest Cisco switching technologies. I received 57 questions and was given 75 minutes to complete the exam. The passing score was 776. The Switching exam requires knowledge of many switching technologies and Cisco switching products. It covers these topics from a Cisco point of view. In this article, I address some of the high points to study for the new exam by mapping to the official objectives, which you'll find here.

	Exam #640-604: Building Cisco Multilayer Switched Networks (Switching) Vendor Cisco Status Live Reviewer's Rating "The Switching exam has been updated to include all the latest Cisco switching technologies; but I found it to be the easiest exam of the four for CCNP." Test Information Apx. 57 questions, 75 minute exam. Cost: $125 (U.S.). . Who Should Take This Exam? Candidates for CCDP and CCNP. Test Objectives Click here

The Cisco Certified Network Professional (CCNP) certification was created by Cisco in 1998. It's used by many IT professionals as a step between CCNA and CCIE. The Switching exam is also a requirement if you choose to pursue the Cisco Certified Design Professional (CCDP). I found the previous version of the Switching exam the easiest of the lot and that hasn't changed with this revision.

The CCDP certification requires you to pass two core exams from the CCNP track (Routing and Switching) as well as the new Designing Cisco Network Architectures (ARCH) exam. You must also hold a valid CCNA and CCDA certification. You can learn more here.

This exam allows you to take a breather after tackling the BSCI (640-603 Routing) exam. There are no simulators or fancy question types such as pick and place or drag and drop. All questions are of the standard multiple-choice format with either select one or a designated number of correct answers. There weren't even any exhibits!

If you have the budget, I highly recommend attending the official Cisco BCMSN course for instructor-led training.

However, you can also use self-study materials. Here are my favorite books:

• Building Cisco Multilayer Switched Networks by Karen Webb, Cisco Press, ISBN 1-5787-0093-0, $60.
• CCNP Practical Studies: Switching (CCNP Self-Study) by Justin Menga, Cisco Press, 1-5872-0060-0, $49.95.
• CCNP: Switching Study Guide by Todd Lammle and Eric Quinn, Sybex, ISBN 0-7821-4153-6, $49.99.

The main objectives of the Switching exam are Cisco switching technologies, Spanning Tree, VLANs and Cisco hardware. You'll find a primer from Cisco here. Below is a more in-depth look at the technologies covered on this exam.

CGMP
In conjunction with Internet Group Management Protocol (IGMP), Cisco Group Management Protocol is used to limit multicast traffic in a switched network. I found this topic covered in much more depth than with previous versions of the exam. Make sure you know how to enable CGMP on distribution layer devices and describe the functionality of CGMP. The new study guides I mentioned have all the information you'll need to learn this and then some.

CGMP frames include the message types Join and Leave, which are used for group membership to control multicast traffic flow.

Enabling CGMP on a switch (connected to a CGMP configured router) is done with the Cisco IOS command:

set cgmp enable

Tip: This exam will require you to know the syntax for both the Cat OS and IOS command set.

Cisco Fundamentals
The exam objective here is to identify the correct Cisco Systems product solution, given a set of network switching requirements.

I was surprised by the number of Cisco product questions in this revision of the exam. You'll need to know the Catalyst product line all the way from 1900 to 8500 and in between, including number of ports, RSM, MLS, Route Processors and Gigabit capabilities. Then there are the "freebie" type questions such as which cable to use when connecting a workstation to a switch (patch).

Tip: Don't forget the three-layer Cisco hierarchical design model: Core, Distribution and Access. Know where you would commonly place different Cisco switch platforms.

Multicast
The objectives in this domain mandate that you be able to describe how switches facilitate multicast traffic and translate multicast addresses into MAC addresses.
Multicast is a process used to transmit a data frame to a host group defined by a single address -- this reduces the network traffic by simultaneously delivering a single stream of information to multiple recipients. As mentioned earlier, CGMP helps to limit multicast traffic and it's this packet that contains the request type (either join or leave) which is sent to a well-known address to which all switches listen. CGMP allows the network routers (acting as CGMP servers) to configure the multicast forwarding table used by switches to indicate their current multicast group membership.

Multicast distribution trees specify a forwarding path between source and destination networks containing members of a multicast group. Because of the dynamic nature of multicast groups with members joining or leaving a group at any time, a distribution tree must be dynamically updated. Branches that contain new members must be added and branches without listeners (multicast members) must be discarded or pruned.

Tip: Although the number of questions on the exam requiring this skill is few, practice converting multicast addresses to MAC addresses.

Multilayer Switching
You'll find many objectives in this domain, including identifying the components necessary to effect multilayer switching, applying flow masks to influence the type of MLS cache, describing layer 2, 3, 4 and multilayer switching, verifying existing flow entries in the MLS cache, describing how MLS functions on a switch and configuring a switch to participate in multilayer switching.

Multilayer Switching (MLS) works by monitoring the frame destined for a router's MAC address. It caches the information and the port used to exit the switch. This is referred to as "route-once, switch-many."

MLS can be implemented in the Catalyst 5000 or 6000 series with a Supervisor Engine and version 4.1(1) or later, IOS release 11.3(2) or later, Supervisor Engine III with the NFFC or a RSFC (Route Switch Feature Card). You can also configure MLS using a Catalyst and an external router.

Flow masks are another topic you should know well. Make sure you understand how they can be applied with the MLS process and filter the entries added to cache. You'll find all the information you need here (PDF download).

If you don't have a good understanding of MLS, you may not know the answers for up to a third of the exam questions!

Spanning Tree
These objectives encompass describing Spanning Tree, configuring the switch devices to improve Spanning Tree convergence in the network, identifying Cisco enhancements that improve Spanning Tree convergence and configuring a switch to distribute traffic on parallel links.

We all learned the terminology, process and basic configuration of Spanning Tree Protocol for the CCNA exam. You'll need to rewind those tapes and set the playback mode to "slow with detail"! Do you remember that STP is used to eliminate loops at layer 2 and negotiate a loop-free path to a root bridge? What about the five port states of STP (blocking, listening, learning, forwarding and filtering)? Do you know how much time is required for a port configured with PortFast to go from blocking to forwarding? (Try 15 seconds.)

PortFast, UplinkFast and BackboneFast are all Cisco STP enhancements available with Catalyst switches. PortFast is the perfect solution for workstations that boot from the network, such as those used by Microsoft Remote Installation Services (RIS) for imaging. UplinkFast allows a blocked port to begin forwarding almost immediately when it detects a failure of a forwarding link. BackboneFast meets specific needs of larger switched networks, when all switches support BackboneFast and inferior BPDUs are received indicating that a link to the root bridge is unavailable.

Configuration of a Cisco switch to support parallel links and load balancing requires the Cat OS command:

set spantree uplinkfast enable

and:

uplink-fast

for IOS. On a Catalyst 5000 the Cat OS command for Backbone Fast is:

set spantree backbonefast

and:

show spantree backbonefast

to confirm.

Tip: BackboneFast is Cisco proprietary implementation and must be supported by all switches in the network.

Switching Interconnectivity
This domain includes several objectives: providing physical connectivity between devices in a switch block, providing connectivity from a user station to an access layer device, providing connectivity between two network devices and configuring a switch for initial operation.

This domain's objectives are a spin-off from the Cisco Fundamentals that I mentioned earlier. You might encounter questions that ask you to identify the Catalyst switches that support Gigabit connections or specify which card you'd find in slot one of the 5000 series switch (Supervisor Engine). Then there are the XL series switches to keep in mind. The 2900XL and 3500XL are designed to be used standalone instead of at the access or distribution layer, because they lack "Cisco enhancements" for STP convergence; these are present in the 2900 and 5000 series.

The Cat OS command:

set ip route default gateway

and IOS command:

ip default-gateway ip-address

is used on the switch to configure a route to other networks.

Troubleshooting
This domain only has one objective: to be able to apply an IOS command set to diagnose and troubleshoot switched network problems. My version of the exam had only a handful of troubleshooting questions. I guess Cisco is saving the bulk of these for the CCNP Support (640-606) test, commonly referred to as the troubleshooting exam! You should be familiar with show commands as used when verifying operation of STP, MLS and VLANs.

Trunking
For this domain you need to be able to describe the different trunking protocols, configure trunking on a switch, maintain VLAN configuration consistency in a switched network, configure the VLAN trunking protocol and describe the Virtual Trunking Protocol (VTP).

ISL, IEEE 802.1Q, LANE and 802.10 are all VLAN identities supported by Cisco as trunking methods. ISL is the proprietary method supported only by Cisco switches and routers. 802.1Q is supported by most switch manufacturers. LANE (LAN Emulation) is the IEEE standard over ATM. 802.10 is another Cisco proprietary method for transporting VLAN identification inside the standard 802.10 frame FDDI.

ISL encapsulates the frame to multiplex VLANs over trunk links with a 26-byte header and 4-byte tail for CRC. 802.1Q actually modifies the original Ethernet frame, which makes the tagging transparent. It supports both access and trunk links.

Tip: Ethernet frames can't exceed 1,518 bytes in size unless the frame is a 802.1Q; then the maximum size is 1,522 bytes.

Configuration of trunking on a switch requires the command:

set trunk mod_num/port_num [on | off | desirable | auto | nonegotiate] vlan_range [isl | dot1q | dot10 | lane | negotiate]

In order to remove a VLAN from a trunk link, the command is:

clear trunk mod_num/port_num vlan_range

Don't forget:

show trunk [mod_num/port_num]

While we're here, remember VTP modes from the CCNA exam (server, client and transparent)? VTP is used to manage VLANs across the campus network. VTP maintains configuration consistency by sending layer 2 trunk frames for addition, deletion and renaming of VLANs. After you have created a VTP management domain, selected switches can be configured not to accept VTP information; this is referred to as transparent. A switch configured as VTP server mode, on the other hand, is used to create, modify and delete vLANs. VTP clients are a "read-only" version of VTP servers! VTP advertisements include management domain, configuration revision number, known VLANs and parameters such as MD5 Digest passwords, which should always be used.

Configuring VTP Trunking Protocol requires the use of a common VTP domain name:

set vtp domain domain_name password password

Each switch is then configured for mode:

set vtp domain domain_name mode [server | client | transparent]

Finally:

show vtp domain

and:

show vtp statistics

will aid in troubleshooting.

VLAN Operations
This is the final domain of the exam. For questions on this topic, you need to be able to describe LAN segmentation using switches, configure a VLAN, ensure broadcast domain integrity by establishing VLANs, facilitate InterVLAN routing in a network containing both switches and routers, and identify the network devices required to effect InterVLAN routing.

When you think of switching, you usually think of layer 2, right? But you should also consider layers 3 and 4. Layer 3 switching is commonly referred to as hardware-based routing. Layer 3 switches operate very much like a traditional router. The difference lies in the physical implementation with the microprocessors and ASICs. Layer 4 switches can make forwarding decisions based on application by looking at the protocol type and port number.

VLANs offer many benefits including broadcast traffic control, security and advanced network management support, to name a few. Configuring a VLAN requires the assignment of switch ports to logical groups that can be controlled statically or dynamically. The Cat OS command:

set vlan vlan_num mod_num/port_list

and the corresponding:

clear vlan

command used on the 5000 series switches configures the assigned ports statically. CiscoWorks 2000 or CiscoWorks for Switched Internetworks (CWSI) can be used for dynamic assignments.

InterVLAN routing is required for campus-wide internetworking. Inter-Switch Link (ISL) is used to facilitate InterVLAN routing by frame tagging, which I discussed earlier in the section on Trunking. I also mentioned the Route Switch Module (RSM), which provides InterVLAN routing support in the Catalyst 5000 series. The Route Switch Feature Card (RSFC) can be used in the 6000.

Tip: The "show module" command can be used to determine all modules installed in a particular switch.

If an external router is used for InterVLAN routing support, a router interface can be logically configured into multiple subinterfaces. After identifying the interface, VLAN encapsulation and assigning the IP address to each subinterface, InterVLAN routing takes place. Being unaware, users can get their work done and praise the networking group

Achieving the CCNP certification is a great accomplishment. After preparing for and passing all four exams, you'll have a much greater appreciation and understanding of networking and Cisco products. Fortunately you don't have to swallow one "big pill" like you did for the CCNA, which covered everything in one exam! Each CCNP exam focuses on a given area for a complete understanding. Good luck!

Andy Barkl, CCNP, CCDP, CISSP, MCT, MCSE:Security, MCSA:Security, A+, CTT+, i-Net+, Network+, Security+, Server+, CNA, has over 19 years of experience in the IT field. He's the owner of MCT & Associates LLC, a technical training and consulting firm in Phoenix, Arizona. He spends much of his time in the classroom but has also been responsible for many Microsoft Windows 2000, Exchange 2000, and Cisco networking deployments for many clients across Arizona. He's also the online editor for MCPMag.com, TCPMag.com, CertCities.com, and a contributing author and editor for Sybex and Cisco Press. He hosts a multitude of exam preparation chats monthly on MCPmag.com, TCPmag.com and CertCities.com. You can reach him at .

More articles by Andy Barkl:

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• Securing Virtual Private Networks (642-511)