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When you begin your CCNA studies, you get hit with a lot of different networking terms right away that you might not be familiar with. What makes it a little more confusing is that a lot of these terms sound a lot alike. Here, we're going to discuss the differences between broadcasts, multicasts, and unicasts at both the Data Link (Layer 2) and Network (Layer 3) layers of the OSI model.

A broadcast is simply a unit of information that every other device on the segment will receive. A broadcast is indicated by having every bit of the address set to its highest possible value. Since a hexadecimal bit's highest value is "f", a hexadecimal broadcast is ff-ff-ff-ff-ff-ff (or FF-FF-FF-FF-FF-FF, as the upper case does not affect hex value). The CCNA exam will demand you be very familiar with hex conversions, so if you're not comfortable with these conversions, get comfortable with them before taking the exam!

At layer 3, a broadcast is indicated by setting every bit in the 32-bit binary string to "1", making the dotted decimal value 255.255.255.255. Every host on a segment will receive such a broadcast. (Keep in mind that switches will forward a broadcast, but routers do not.) In contrast to a broadcast, a unicast is a packet or frame with only one destination.
{mosgoogle}
There is a middle ground between broadcasts and unicasts, and that is a multicast. Where a broadcast will be received by all, and a unicast is received by only one host, a multicast will be received by multiple hosts, all belonging to a "multicast group". As you climb the Cisco certification pyramid, you'll be introduced to creating multicast groups and controlling multicast traffic, but for your CCNA studies you need only keep certain multicast groups in mind.

Class D addresses are reserved for multicasting this range is 224.0.0.0 - 239.255.255.255. The addresses 224.0.0.0 - 224.255.255.255 are reserved for use by network protocols on a local network segment, and like broadcasts, routers will not forward these multicast packets. (Packets with these addresses are sent with a Time To Live of 1.)

As a CCNA candidate, you should know that OSPF routers use the address 224.0.0.5 to send hellos, EIGRP routers use 224.0.0.10 to send updates, and RIP version 2 uses 224.0.0.9 to send routing updates. RIP version 1 and IGRP both broadcast their updates.

Multicasting gets a bit more complicated as you go from your CCNA to the CCNP and CCIE, but by simply understanding what multicasting is, you go a long way toward securing the CCNA.


Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

CCNA / CCNP candidates are going to be drilled by Cisco when it comes to troubleshooting questions. You're going to have to be able to analyze configurations to see what the problem is (and if there is a problem in the first place), determine the meaning of different debug outputs, and show the ability not just to configure a router or switch, but troubleshoot one.

 

That's just as it should be, because CCNAs and CCNPs will find themselves doing a lot of troubleshooting in their careers. Troubleshooting isn't something that can just be learned from a book; you've got to have some experience working with routers and switches. The only real way to learn how to troubleshoot is to develop that ability while working on live equipment.

Of course, your company or client is going to take a very dim view of you developing this skill on their live network. So what can you do?
{mosgoogle}
Assemble a Cisco home lab. When you start working with real Cisco equipment, you're doing yourself a lot of favors. First, you're going to be amazed at how well you retain information that will become second nature to you before exam day. But more importantly, both for the exam room and your career, you're developing invaluable troubleshooting skills.

Don't get me wrong, I'm not saying knowing the theory of how routers and switches work is unimportant. Quite the opposite - if you don't know networking theory, you're not going to become a CCNA or CCNP. But the ability to apply that knowledge is vital - and the only way you can get that is to work on real Cisco routers and switches. As for these "router simulators" on the market today, ask yourself this simple question: "When I walk into a server room, how many router simulators do I see?"

I often tell students that they'll do their best learning when they screw something up. I've had many a student tell me later that I was right - when they misconfigured frame relay, ISDN, or another CCNA / CCNP technology and then had to fix it themselves, it not only gave them the opportunity to apply their knowledge, but it gave them the confidence to know they could do it.

And you can't put a price on confidence - in the exam room or in the network center!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

One question I’m often asked by CCNA candidates is whether to take the “one big exam”, or take the two separate exams required by Cisco to achieve the Cisco Certified Network Associate (CCNA) exam.

The question comes up because there are now two separate paths to the CCNA certification. Candidates may take a single exam, 640-811, or two exams, 640-821 and 640-811.

 

What’s the difference? The two-exam approach involves exams with different topics and therefore different preparation techniques. 640-821 is the Introduction To Cisco Networking Technologies exam. This course does introduce the candidate to Frame Relay, PPP, and other WAN technologies, but goes into little detail. Emphasis in the Intro course is placed on knowing how Ethernet behaves, how different types of cable are used for different purposes, and knowing what cable to use in a certain situation. The candidate should expect some questions involving binary math as well, but they will involve fairly simple conversions.

The 640-811 exam, Interconnecting Cisco Networking Devices, goes into much more detail on WAN technologies. Routing and switching behavior are covered, and the candidate is expected to answer difficult questions involving binary math and subnetting as well. The candidate may also have to demonstrate ability to configure a router or switch via a simulator. Since the ICND exam goes into more detail, it’s generally considered the more difficult exam.
{mosgoogle}
The approach I recommend to a CCNA candidate depends on their background. If the candidate is a relative newcomer to networking, or hasn’t taken a certification exam before, I recommend they take the two-exam approach. This allows the candidate to focus only on the Intro topics, and gives them a strong sense of confidence after passing the Intro exam. That confidence flows over into the ICND exam.

For those who have networking experience, and are very familiar with Ethernet behavior and cable types, I recommend the one-exam approach. This allows the candidate to focus on the more advanced topics they’ll be seeing in the single exam, while spending just a little time reviewing their Intro-level knowledge.

Regardless of the approach you choose, the path to true CCNA success remains the same. Get some real hands-on experience, either by renting rack time online or by putting together your own home lab. Understand what’s going on “beneath the command”; don’t use router commands when you don’t understand what they’re doing. Add to that a true mastery on binary math, and you’re on your way to having the magic letters “CCNA” behind your name!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

CCNA FAQ

Q. What exams do I have to take to get my CCNA?

A. The CCNA (Cisco Certified Network Associate) certification offers two paths. You can take the one-exam path by taking the 640-801 CCNA Composite exam. If you want to break it up into two parts, you can take the Introduction To Cisco Networking Technologies (INTRO 640-821) and the Interconnecting Cisco Networking Devcies (ICND 640-811) exams.

 

Q. Chris, which path do you recommend?

A. I generally recommend the two-exam path, particularly for those CCNA candidates that haven't taken a Cisco exam before. The Intro exam offers you a little more time and allows you to become comfortable with the Cisco exam engine, particularly the simulator questions. Let's face it, the CCNA single exam covers a lot of material, from basic networking to OSPF to router on a stick. Most candidates are better off breaking this huge amount of material into two distinct parts.

Don't get me wrong, I've had plenty of students and customers pass the CCNA composite. It can be done!
{mosgoogle}
Q. Do I have to recertify my CCNA, or is it mine forever after I pass?

A. One way Cisco protects the value of its certifications is to enforce strict recertification policies. When you earn your CCNA, you must recertify within three years.

Q. How do I recertify my CCNA?

A. There is a lot of confusion out there on this question. The latest information from Cisco is that you recertify your CCNA by doing any of the following three things:

1. Pass the current CCNA Composite or ICND exam.

2. Pass any 642-level professional level exam or any Cisco Qualified Specialist exam, not including Sales Specialist exams.

3. Pass any CCIE written exam.

Q. How do I register for the CCNA exam?

A. You can take the CCNA exam at any Prometric or VUE testing center. To find a Prometric testing center near you and register online, visit www.2test.com . For a VUE site, register at www.vue.com .

Q. Can you give me a braindump for the exam?

A. Boy, do you have the wrong guy!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

A Cisco access server is generally the last item a CCNA or CCNP candidate has on their mind when they're putting together a home lab. The thinking tends to be that since this router isn't really doing anything in the production part of your practice lab, it's not really important.Once you have more than two devices in your home lab, though, you'll realize that constantly moving the console cable around from one router to another gets very tiresome. That's what an access server does for a home lab - it allows you to connect your PC to a single device when working in your home lab, with no need to constantly disconnect and reconnect the console cable. The console cable will be connected directly to the access server, and the access server is connected to all the other devices in your home lab. Once you start working with one, you'll wonder how you got along without it!

The term "access server" is a little misleading. This is not a server in the traditional sense, it's a Cisco router with asynchronous serial ports. It is these ports that you'll use to connect to the other devices in your home lab. Two affordable models of access servers are Cisco 2509s and Cisco 2511s. They can be found on ebay as well as other vendors on the Net.
{mosgoogle}
You will also need an octal cable. On one end, the cable has a large connector that will connect to the access server. The other end is actually eight separate cables, each with RJ-45 connectors. These connectors are numbered 1 - 8 and will be connected to the console port on each router and switch. It is important to note the number on each connector you're connecting to the other lab devices.

Now that you've got the physical equipment, let's take a look at a typical configuration of an access server:

no service password-encryption

no service udp-small-servers

no service tcp-small-servers

!
hostname BRYANT_ADVANTAGE_AS4


no ip domain-lookup

ip host r1 2001 10.4.4.4

ip host r2 2002 10.4.4.4

ip host r3 2003 10.4.4.4

ip host sw1 2004 10.4.4.4

ip host sw2 2005 10.4.4.4

ip host FrameSwitch 2006 10.4.4.4


interface Loopback555

ip address 10.4.4.4 255.255.255.0


line con 0

exec-timeout 0 0

logging synchronous

line 1 16

no exec

transport input all


You can assign any loopback address and number here the important thing to note is that the IP HOST table you will build constantly refers back to the loopback address on the access server.

In this configuration, I have the octal cable's connector 1 in R1, 2 in R2, 3 in R3, 4 in SW1, 5 in SW2, and 6 in my frame relay switch. The number "2001" in the first line of the IP HOST table refers to that connector. That's why it is important to note the number on a given connector you place in the console port of a router or switch.

The asynchonous lines are identified by "line 1 16". This access server has 16 possible connections many will just have 8, which is usually plenty. Regardless of how many lines you have, you'll need the commands transport input all and no exec to allow reverse telnet to work effectively.

There's one more thing to watch out for. When you first connect to the AS for a practice session, you will need to open the line to each device by using the full hostname of the device as shown in the IP HOST table. Here, you would begin by entering R1, R2, R3, SW1, SW2, and FrameSwitch to open the line to each device. After that, you need to enter the line number - 1, 2, 3, 4, 5, and 6. It sounds a little confusing at first, but after just a few minutes of practice you'll be doing it without even thinking about it.

When you are working in your home lab, you will not go from one device to another that is, when you are done on R1 and want to configure R2, you must go back to the access server and then to R2. The keystroke to do this is . Again, it may sound complicated, but after a little practice you will again do this without thinking about it.

Adding an access server to your CCNA or CCNP home lab may not be on your mind now, but once you add a few more routers or switches to the lab, you'll want to spend more time configuring and practicing and less time moving a cable around. And once you get one, you'll wonder how you did without it!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

One of the major topics on your CCNA and CCNP exams is Frame Relay. Additionally, Frame Relay is one of the most popular WAN technolgies in today's networks. Getting hands-on experience with Frame Relay in Cisco networks isn't just a good idea, it's a necessity. Let's face it, your employer is going to get a little touchy if you start experimenting with your network's Frame Relay setup.

 

To practice all your important Frame Relay commands for your exams, you need a working Frame Relay cloud in your home lab. A production network's Frame cloud consists of a lot of Frame switches, but if you choose wisely, a single Cisco router can act as your home lab's entire Frame cloud!

Before we look at the configuration of such a router (hereafter referred to as a "frame relay switch"), let's look at the physical requirements.

The more serial ports you have, the better. You should get a router with at least four serial ports. For frame switching purposes, it doesn't matter if the ports are synchronous or asynchronous - you just need the ports.
{mosgoogle}
You will also need some DTE/DCE cables. The DCE end of the cables will be connected to the frame switch.

A great configuration for a CCNA practice lab is three routers that serve as "production" routers, and a 4th router as a frame relay switch. (You'll want an access server as well, but that's another article.)

What I use in my student and customer pods is a setup where R1 is connected to the frame switch's S1 port, R2 is connected to S2 on the frame switch, and R3 is connected to the frame switch's S3 port.

Now comes the tricky part - the configuration. A frame relay switch's config can be hard to find, so here's a copy of mine. Pay particular attention to the config on ports s1, s2, and s3.

version 12.0

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname FRAME_SWITCH

!

!

ip subnet-zero

no ip domain-lookup

frame-relay switching

!

!

!

interface Ethernet0

no ip address

no ip directed-broadcast

shutdown

!

interface Serial0

ip address 10.1.1.2 255.255.255.0

clockrate 56000

!

interface Serial1

no ip address

no ip directed-broadcast

encapsulation frame-relay

logging event subif-link-status

logging event dlci-status-change

clockrate 56000

no frame-relay inverse-arp

frame-relay intf-type dce

frame-relay route 122 interface Serial2 221

frame-relay route 123 interface Serial3 321

!

interface Serial2

no ip address

no ip directed-broadcast

encapsulation frame-relay

logging event subif-link-status

logging event dlci-status-change

clockrate 56000

no frame-relay inverse-arp

frame-relay intf-type dce

frame-relay route 221 interface Serial1 122

!

interface Serial3

no ip address

no ip directed-broadcast

encapsulation frame-relay

logging event subif-link-status

logging event dlci-status-change

clockrate 56000

no frame-relay inverse-arp

frame-relay intf-type dce

frame-relay route 321 interface Serial1 123

!

interface BRI0

ip address 150.1.1.1 255.255.255.252

no ip directed-broadcast

encapsulation ppp

dialer map ip 150.1.1.2 name R2 broadcast 2335552221

dialer-group 1

!

ip classless

!

dialer-list 1 protocol ip permit

!

line con 0

exec-timeout 0 0

logging synchronous

transport input none

line aux 0

line vty 0 4

login

!

end

The key command in the global configuration is frame-relay switching. You must have this configured before you can configure the interfaces.

The interfaces will be configured with the frame route command. Let's take a look at what each value means in the command frame-relay route 122 interface Serial2 221.

frame-relay route - the command

122 - the incoming DLCI on this interface

interface serial2 - the interface the data will be sent out

221 - the outgoing DLCI

This command on S1 means that anything that comes in on this port on DLCI 122 will be sent out interface serial2 on DLCI 221.

It's a good idea to hard-code the interfaces to act as DCEs with the frame intf-type dce command. Since these interfaces are acting as DCEs, the clockrate command is needed for the line protocol to come up.

Once you've configured your frame switch as shown and have configured the frame map statements on the "production" routers, you can test the frame switch configuration. On the frame switch, run the command show frame route.

FRAME_SWITCH#show frame route

Input Intf Input Dlci Output Intf Output Dlci Status

Serial1 122 Serial2 221 active

Serial1 123 Serial3 321 active

Serial2 221 Serial1 122 active

Serial3 321 Serial1 123 active

You should see "active" for all the interfaces. If you see "deleted", make sure your frame switch interfaces are open if they are, check the router configs.

Keep in mind that you can still configure routing protocols to run on ports that you're not using for frame switching. The router we used here had an ethernet port and BRI port, and the BRI port has been configured as part of the production network. Running frame switching does not disable IP routing.

Purchasing and configuring your own frame relay switch is an invaluable part of your Cisco education. By practicing your frame commands and configuring frame connections over your own frame relay cloud, you're polishing your Cisco skills and gaining knowledge that cannot be duplicated by simulator programs.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

When I first started studying for my CCNP, some of the concepts of OSPF really confused me. This was especially true for the ASBR, stub areas, and total stub areas. Sure, I could memorize the LSA types associated with these devices and area types, but there just weren't any illustrations that explained exactly what was going on.

 

This CCNP tutorial shows an ASBR in operation, and also introduces you to a basic example of route redistribution. Don't worry, it gets more complicated. :)

Here's the network we'll be working with in this tutorial:

R5
|
R1
/
R2 R3

Networks:

R1 - R5 Ethernet Segment: 10.1.1.0 /24

R1 - R2 - R3 Serial Segment: 172.16.123.0 /24 (Preconfigured with OSPF)

R1 and R5 are running RIP over their common Ethernet segment, 10.1.1.0 /24. R5 has three loopbacks it will be advertising into the RIP domain.

R1 is also running OSPF, with R2 and R3 as neighbors. Even though R1 knows about the loopbacks on R5, its OSPF neighbors do not. R1 has these routes in its RIP routing table, and for OSPF neighbors to learn of these routes, route redistribution must be manually configured.
{mosgoogle}
R5#conf t

R5(config)#router rip

R5(config-router)#version 2

R5(config-router)#no auto-summary

R5(config-router)#network 5.0.0.0

R5(config-router)#network 10.0.0.0

R1#conf t

R1(config)#router rip

R1(config-router)#version 2

R1(config-router)#no auto-summary

R1(config-router)#network 10.0.0.0

R1#show ip route rip

5.0.0.0/24 is subnetted, 3 subnets

R 5.1.1.0 [120/1] via 10.1.1.5, 00:00:10, Ethernet0

R 5.2.1.0 [120/1] via 10.1.1.5, 00:00:10, Ethernet0

R 5.3.1.0 [120/1] via 10.1.1.5, 00:00:10, Ethernet0

R1 has a route for all three of R5’s loopback interfaces, learned via RIP. R1 is also running OSPF, but its neighbors R2 and R3 don’t know about these RIP routes:

R2#show ip route ospf

R2# < no output from show command means no routes! >

R3#show ip route ospf

R3#

Be careful when configuring redistribution use IOS Help to make sure you’re not missing any vital options. IOS Help shows that there is a “subnets” option when redistributing RIP into OSPF. If that is left off, only classful networks are redistributed (as the router is kind enough to tell us). In this case, we have no classful networks, so there will be no redistribution. R2 will not see the RIP routes.

R1(config)#router ospf 1

R1(config-router)#redistribute rip?

metric Metric for redistributed routes

metric-type OSPF/IS-IS exterior metric type for redistributed routes

route-map Route map reference

subnets Consider subnets for redistribution into OSPF

tag Set tag for routes redistributed into OSPF


R1(config-router)#redistribute rip

% Only classful networks will be redistributed



R2#show ip route ospf

R2#clear ip route *

R2#show ip route ospf

R2#

On R1, we’ll now use the “subnets” option, and the RIP subnets are successfully redistributed into OSPF.

R1(config)#router ospf 1

R1(config-router)#redistribute rip subnets

R2 now sees the redistributed routes.

R2#show ip route ospf

5.0.0.0/24 is subnetted, 3 subnets

O E2 5.1.1.0 [110/20] via 172.12.123.1, 00:00:08, Serial0.123

O E2 5.2.1.0 [110/20] via 172.12.123.1, 00:00:08, Serial0.123

O E2 5.3.1.0 [110/20] via 172.12.123.1, 00:00:08, Serial0.123

10.0.0.0/24 is subnetted, 1 subnets

O E2 10.1.1.0 [110/20] via 172.12.123.1, 00:00:08, Serial0.123

Notice that the routes are marked as “E2”. The E indicates that these are external routes these are routes that were learned by OSPF via redistribution.

Naturally, you’ll want to ping these networks to make sure you have two-way communication. Even though the routes to these loopbacks are in the routing table, pings fail:

R2#ping 5.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 5.1.1.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)



Keep this in mind when troubleshooting: It’s not enough to have a route to a destination for pings to succeed there’s got to be a path back. At this point, R5 doesn’t know where the 172.12.123.0 network is, so there’s no way the ping can get back. More route redistribution is necessary on R1.

Your first instinct may be to redistribute OSPF routes into RIP to make this work, but remember that the 172.12.123.0 /24 network isn’t known to R1 via OSPF it’s a directly connected network. We can redistribute connected networks into RIP to give R5 a route to 172.12.123.0 /24, which will give the ICMP packets a path back to R2, which will allow pings to succeed.



R1(config)#router rip

R1(config-router)#redistribute connected



R5#show ip route rip

1.0.0.0/32 is subnetted, 1 subnets

R 1.1.1.1 [120/1] via 10.1.1.1, 00:00:02, Ethernet0

172.12.0.0/24 is subnetted, 1 subnets

R 172.12.123.0 [120/1] via 10.1.1.1, 00:00:02, Ethernet0



R2#ping 5.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 5.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 68/69/76 ms



Performing this redistribution makes R1 an ASBR, as shown here with show ip ospf. This command even shows you what protocol(s) are being redistributed into OSPF.

R1#show ip ospf

Routing Process "ospf 1" with ID 1.1.1.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

It is an autonomous system boundary router

Redistributing External Routes from,

rip, includes subnets in redistribution

Knowing exactly what the ASBR does and how to configure route redistribution are just a few of the many OSPF skills you'll need to earn your CCNP. Like any other Cisco skill, breaking a complex topic like OSPF down into smaller, manageable pieces is the best way to master these topics and pass the CCNP exams.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

OSPF is a major topic on both the CCNA and CCNP exams, and it's also the topic that requires the most attention to detail. Where dynamic routing protocols such as RIP and IGRP have only one router type, a look at a Cisco routing table shows several different OSPF route types.

 

R1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
In this tutorial, we'll take a look at the difference between two of these route types, E1 and E2.
Route redistribution is the process of taking routes learned via one routing protocol and injecting those routes into another routing domain. (Static and connected routes can also be redistributed.) When a router running OSPF takes routes learned by another routing protocol and makes them available to the other OSPF-enabled routers it's communicating with, that router becomes an Autonomous System Border Router (ASBR).
Let's work with an example where R1 is running both OSPF and RIP. R4 is in the same OSPF domain as R1, and we want R4 to learn the routes that R1 is learning via RIP. This means we have to perform route redistribution on the ASBR. The routes that are being redistributed from RIP into OSPF will appear as E2 routes on R4:
R4#show ip route ospf
{mosgoogle}
O E2 5.1.1.1 [110/20] via 172.34.34.3, 00:33:21, Ethernet0

6.0.0.0/32 is subnetted, 1 subnets

O E2 6.1.1.1 [110/20] via 172.34.34.3, 00:33:21, Ethernet0

172.12.0.0/16 is variably subnetted, 2 subnets, 2 masks

O E2 172.12.21.0/30 [110/20] via 172.34.34.3, 00:33:32,
Ethernet0

O E2 7.1.1.1 [110/20] via 172.34.34.3, 00:33:21, Ethernet0

15.0.0.0/24 is subnetted, 1 subnets

O E2 15.1.1.0 [110/20] via 172.34.34.3, 00:33:32, Ethernet0

E2 is the default route type for routes learned via redistribution. The key with E2 routes is that the cost of these routes reflects only the cost of the path from the ASBR to the final destination; the cost of the path from R4 to R1 is not reflected in this cost. (Remember that OSPF's metric for a path is referred to as "cost".)
In this example, we want the cost of the routes to reflect the entire path, not just the path between the ASBR and the destination network. To do so, the routes must be redistributed into OSPF as E1 routes on the ASBR, as shown here.
R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router ospf 1

R1(config-router)#redistribute rip subnets metric-type 1

Now on R4, the routes appear as E1 routes and have a larger metric, since the entire path cost is now reflected in the routing table.
O E1 5.1.1.1 [110/94] via 172.34.34.3, 00:33:21, Ethernet0

6.0.0.0/32 is subnetted, 1 subnets

O E1 6.1.1.1 [110/100] via 172.34.34.3, 00:33:21, Ethernet0

172.12.0.0/16 is variably subnetted, 2 subnets, 2 masks

O E1 172.12.21.0/30 [110/94] via 172.34.34.3, 00:33:32, Ethernet0

O E1 7.1.1.1 [110/94] via 172.34.34.3, 00:33:21, Ethernet0

15.0.0.0/24 is subnetted, 1 subnets

O E1 15.1.1.0 [110/94] via 172.34.34.3, 00:33:32, Ethernet0


Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

CCNA and CCNP candidates are well-versed in Spanning-Tree Protocol, and one of the great things about STP is that it works well with little or no additional configuration. There is one situation where STP works against us just a bit while it prevents switching loops, and that is the situation where two switches have multiple physical connections.You would think that if you have two separate physical connections between two switches, twice as much data could be sent from one switch to the other than if there was only one connection. STP doesn't allow this by default, however in an effort to prevent switching loops from forming, one of the paths will be blocked.

SW1 and SW2 are connected via two separate physical connections, on ports fast0/11 and fast 0/12. As we can see here on SW1, only port 0/11 is actually forwarding traffic. STP has put the other port into blocking mode (BLK).


SW1#show spanning vlan 10


(some output removed for clarity)


Interface Role Sts Cost Prio.Nbr Type


Fa0/11 Root FWD 19 128.11 P2p

Fa0/12 Altn BLK 19 128.12 P2p


While STP is helping us by preventing switching loops, STP is also hurting us by preventing us from using a perfectly valid path between SW1 and SW2. We could literally double the bandwidth available between the two switches if we could use that path that is currently being blocked.
{mosgoogle}
The secret to using the currently blocked path is configuring an Etherchannel. An Etherchannel is simply a logical bundling of 2 - 8 physical connections between two Cisco switches.

Configuring an Etherchannel is actually quite simple. Use the command "channel-group 1 mode on" on every port you want to be placed into the Etherchannel. Of course, this must be done on both switches if you configure an Etherchannel on one switch and don't do so on the correct ports on the other switch, the line protocol will go down and stay there.

The beauty of an Etherchannel is that STP sees the Etherchannel as one connection. If any of the physical connections inside the Etherchannel go down, STP does not see this, and STP will not recalculate. While traffic flow between the two switches will obviously be slowed, the delay in transmission caused by an STP recalculation is avoided. An Etherchannel also allows us to use multiple physical connections at one time.

Here's how to put these ports into an Etherchannel:

SW1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW1(config)#interface fast 0/11

SW1(config-if)#channel-group 1 mode on

Creating a port-channel interface Port-channel 1


SW1(config-if)#interface fast 0/12

SW1(config-if)#channel-group 1 mode on



SW2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW2(config)#int fast 0/11

SW2(config-if)#channel-group 1 mode on

SW2(config-if)#int fast 0/12

SW2(config-if)#channel-group 1 mode on


The command "show interface trunk" and "show spanning-tree vlan 10" will be used to verify the Etherchannel configuration.


SW2#show interface trunk (some output removed for clarity)


Port Mode Encapsulation Status Native vlan

Po1 desirable 802.1q trunking 1


SW2#show spanning vlan 10 (some output removed for clarity)


Interface Role Sts Cost Prio.Nbr Type


Po1 Desg FWD 12 128.65 P2p


Before configuring the Etherchannel, we saw individual ports here. Now we see "Po1", which stands for the interface "port-channel1". This is the logical interface created when an Etherchannel is built. We are now using both physical paths between the two switches at one time!

That's one major benefit in action let's see another. Ordinarily, if the single open path between two trunking switches goes down, there is a significant delay while another valid path is opened - close to a minute in some situations. We will now shut down port 0/11 on SW2 and see the effect on the etherchannel.

SW2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW2(config)#int fast 0/11

SW2(config-if)#shutdown

3w0d: %LINK-5-CHANGED: Interface FastEthernet0/11, changed
state to administratively down


SW2#show spanning vlan 10


VLAN0010

Spanning tree enabled protocol ieee

Interface Role Sts Cost Prio.Nbr Type


Po1 Desg FWD 19 128.65 P2p



SW2#show interface trunk


Port Mode Encapsulation Status Native vlan


Po1 desirable 802.1q trunking 1

The Etherchannel did not go down! STP sees the Etherchannel as a single link therefore, as far as STP is concerned, nothing happened.


Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!

A CCNA or CCNP candidate who wants to be totally prepared for their exams is going to put together a home lab to practice on. With used Cisco routers and switches more affordable and plentiful then ever before, there's really no excuse to not have one!

 

With the many different models available, there is some understandable confusion among future CCNAs and CCNPs about which routers to buy and which ones to avoid. You can take almost any set of Cisco routers and put together a home lab; part of the learning process is taking what equipment you have available and putting together your own lab! For those of you preparing to start your home lab or add to your existing one, this article will list the routers I use in my Cisco pods. You certainly don't have to have all this equipment, but this will give you some good ideas on how to get started.

The most versatile router you can get for your CCNA / CCNP home lab is a 2520. These routers come with four serial ports, one ethernet port, and one BRI interface for ISDN practice. This mix of interfaces means you can actually use it as a frame relay switch while using the ethernet and BRI ports for routing. (There is no problem with using a lab router as both your frame relay switch and a practice router; for a frame relay switch sample configuration, visit my website!)

My pods consist of five routers and two switches, and three of the five routers are 2520s, due to their versatility. A recent ebay search showed these routers selling for $99 - $125, an outstanding value for the practice you're going to get.
{mosgoogle}
I also use 2501s in my home labs. These have fewer interfaces, but the combination of two serial interfaces and one ethernet interface allows you to get plenty of practice.

A combination that works very well is using three 2520s; one as my dedicated frame relay switch, one as R1, and another as R2. Add a 2501 as R3, and you can have a frame cloud connecting R1, R2, and R3, a direct serial connection between R1 and R3, an Ethernet segment that includes all three routers, and an ISDN connection between R1 and R2 if you have an ISDN simulator. That combination will allow you to get a tremendous amount of practice for the exams, and you can always sell it when you're done!

2501s are very affordable, with many in the $50 range on ebay. It's quite possible to get three 2520s and one 2501 for less than $500 total, and you can get most of that money back if you choose to sell it when you're done.

With four routers to work with, you're probably going to get tired of moving that console cable around. An access server (actually a Cisco router, not the white boxes we tend to think of when we hear "server") will help you out with that. An access server allows you to set up a connection with each of your other routers via an octal cable, which prevents you from moving that console cable around continually. For an example of an access server configuration, just visit my website and look in the "Free Training" section.

Access server prices vary quite a bit; don't panic if you do an ebay search and see them costing thousands of dollars. You do NOT need an expensive access server for your CCNA / CCNP home lab. 2511s are great routers to get for your access server.

One question I get often from CCNA / CCNP candidates is "What routers should I buy that I can still use when I'm ready to study for the CCNP?" The CCIE lab changes regularly and sometimes drastically when it comes to the equipment you'll need. During my CCIE lab studies, I found that renting time from online rack rental providers was actually the best way to go. Don't hesitate when putting your CCNA / CCNP home lab together, wondering what will be acceptable for the CCIE lab a year or so from now. None of us know what's going to be on that equipment list, so get the CCNA and CCNP first - by building your own Cisco home lab!


Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the CCNA exam and CCNP exam with Chris Bryant, CCIE #12933!

For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, just visit the website and claim your free copies!