CCNP Tutorial For The BSCI Exam

Configuring ISIS Over Frame Relay

Vital Reading And Watching For All Cisco Certification Candidates:

The July 2010 CCNP Changes (And How To Beat Them!)

In the previous BSCI tutorials on ISIS, we examined the theory of ISIS routing in detail - and now we're going to configure ISIS and put our theory into action.

There are two keys to remember when you're configuring ISIS in the real world or on the BSCI exam:

1. The NET address is configured under the ISIS process, not on an interface.

2. Configure the ip router isis command on the appropriate interfaces.

We'll start our configuration by creating ISIS adjacencies over Frame Relay. Each router will be in its own area, and the configurations follow the illustration. We'll add a broadcast segment later in this section.

The DLCIs aren't shown in the diagram, but they are shown in the frame relay ip statements that were configured before we started this lab - so we'll use those same DLCIs for our frame relay clns statements.

You can use frame map clns statements to configure ISIS over a frame relay network. Note that we have frame map statements for both CLNS and IP.

Also note that this is a full-mesh configuration over Frame, not the typical hub-and-spoke network we use in other labs.

Router 2:

interface Serial0/1
  ip address 172.12.123.2 255.255.255.0
  ip router isis
  encapsulation frame-relay
  frame-relay map clns 105 broadcast
  frame-relay map clns 104 broadcast
  frame-relay map ip 172.12.123.4 104 broadcast
  frame-relay map ip 172.12.123.5 105 broadcast
  no frame-relay inverse-arp

router isis
  net 49.0002.2222.2222.2222.00

Router 4:

interface Serial0/0
  ip address 172.12.123.4 255.255.255.0
  ip router isis
  encapsulation frame-relay
  frame-relay map clns 405 broadcast
  frame-relay map clns 401 broadcast
  frame-relay map ip 172.12.123.2 401 broadcast
  frame-relay map ip 172.12.123.5 405 broadcast
  no frame-relay inverse-arp

router isis
  net 49.0004.4444.4444.4444.00

Router 5:

interface Serial0/1
  ip address 172.12.123.5 255.255.255.0
  ip router isis
  encapsulation frame-relay
  frame-relay map clns 501 broadcast
  frame-relay map clns 504 broadcast
  frame-relay map ip 172.12.123.2 501 broadcast
  frame-relay map ip 172.12.123.4 504 broadcast
  no frame-relay inverse-arp

router isis
  net 49.0005.5555.5555.5555.00

You know the drill at this point of any routing protocol configuration - check those adjacencies! We'll do that with the show clns neighbors command.

Note the value for the SNPA is the DLCI number, since the segment is running over frame relay. Otherwise, a MAC address would appear here.

R2#show clns neighbors

System Id      Interface      SNPA                State  Holdtime  Type Protocol
R4                  Se0/1       DLCI 104                 Up     29              L2   IS-IS
R5                  Se0/1       DLCI 105                 Up     9                L2   IS-IS

To see more detailed information about ISIS neighbors, including their area ID, run show clns neighbors detail.

R2#show clns neighbors detail

System Id      Interface   SNPA                State  Holdtime  Type Protocol
R4                 Se0/1       DLCI 104            Up          29         L2   IS-IS
Area Address(es): 49.0004
  IP Address(es):  172.12.123.4*
  Uptime: 00:19:09
  NSF capable

R5                  Se0/1       DLCI 105            Up            8         L2   IS-IS
Area Address(es): 49.0005
  IP Address(es):  172.12.123.5*
  Uptime: 00:18:26
  NSF capable

We'll continue this lab right after this important message!

Earn Your CCNP With The Personal Guarantee Of Chris Bryant, CCIE #12933:

“I GUARANTEE You'll Pass The Current CCNP Exams - BSCI, ONT, ISCW, and BCMSN - Before The July 31, 2010 Cutoff Date With My CCNP Study Packages ...

... And If You Don't Pass FOR ANY REASON Before That Time, I'll Give You a 100% Free CCNP Study Package Download For The New Exam Track!"

You Also Get A FREE CCNA Security Study Package, Valued at $67, With The Purchase Of Any CCNP Study Package!

Let's get back to the ISIS lab!

Another vital ISIS show command is show clns interface .  You can run that command as-is, or narrow the output down by following the command with the interface type and number.

There's quite a bit of output here, but it's important output! I've bolded and numbered six important points in the following output - the explanations for each of the numbered items can be found at the end of this output.

R2#show clns interface serial 0/1
Serial0/1 is up, line protocol is up
  Checksums enabled, MTU 1500, Encapsulation FRAME-RELAY
  ERPDUs enabled, min. interval 10 msec.
  CLNS fast switching enabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 16 seconds
  Routing Protocol: IS-IS
Circuit Type: level-1-2  (1)
    Interface number 0x0, local circuit ID 0x1
    Level-1 Metric: 10, Priority: 64, Circuit ID: R2.01
    DR ID: 0000.0000.0000.00
    Level-1 IPv6 Metric: 10
    Number of active level-1 adjacencies: 0
Level-2 Metric: 10, Priority: 64, Circuit ID: R5.01 (2)
DR ID: R5.01  (3)
Level-2 IPv6 Metric: 10 (4)
Number of active level-2 adjacencies: 2  (5)
Next IS-IS LAN Level-1 Hello in 4 seconds  (6)
    Next IS-IS LAN Level-2 Hello in 2 seconds  (6)

1 - The circuit type is the Cisco default, L1/2.

2 - The default metric for ISIS is 10; the default priority is 64.  The ISIS metric is also referred to as cost or default. 

ISIS can also use delay, expense, and error as metrics, but Cisco does not support these.

3 -   The DIS (Designated Intermediate System) for this segment is R5.  Since we're running ISIS over frame relay, the router running the highest DLCI is the DIS.

4 -   Again, the default metric is 10.

5 - The number of L2 adjacencies is shown.

6 - Note that even though this router has no L1 adjacencies, it continues to send out both L1 and L2 Hellos.

Now that we've confirmed our adjacencies over the Frame Relay cloud, we need to add a couple of broadcast segments and then we'll add some routes to our ISIS network!

We'll now add some routers and segments as shown below:

We'll add those Ethernet segments and some ISIS routes to our network in the next section of this exclusive ISIS tutorial.

Look for that section on our CCNP BSCI Tutorial page on Saturday, March 5!

Chris Bryant

CCIE #12999

"The Computer Certification Bulldog"

chris@thebryantadvantage.com

As a CCNP candidate, you know how link state protocols work, and this gives you quite the advantage when it comes to learning ISIS.  When I was studying for the CCNP, I found the most difficult part of my ISIS study was learning the terminology. 

Once you get used to the terminology, you'll find ISIS relatively easy to work with, since much of its operation is similar to OSPF.

The terminology for ISIS is totally different from OSPF, however - ISIS even refers to routers and hosts with terms you probably haven't even heard unless you've been exposed to this protocol before.  Again, you're going to see many similarities between ISIS and OSPF -- it's just that the terms we use are different. 

ISIS was removed as a CCIE Routing & Switching lab topic in 2006, and that move led some people to refer to ISIS as "dead". 

ISIS is used often by Internet Service Providers (ISPs).  I'll be the first to say that you might not see much ISIS outside of ISPs, but it's hardly "dead" and is well worth learning.

Besides, it's definitely going to be on your BSCI exam!

ISIS was originally designed for the Open System Interconnection (OSI) protocol suite.  The Connectionless Network Service (CLNS) is used by OSI protocols, and the Layer 3 routing protocol used is Connectionless Network Protocol (CLNP). 

ISIS is one of two protocols defined by the OSI at the network layer. The other is the ESIS router discovery protocol. Of these two, the focus for your BSCI exam is ISIS. 

The form of ISIS running on Cisco routers is Integrated ISIS , which supports both CLNP and IP.

ISIS uses a two-level hierarchy, allowing a large domain to be subdivided into areas. (Sounds familiar!) Before discussing these area types, let's take a look at how OSI defines certain familiar network terms.

An OSI domain is very much like a domain with the other routing protocols you've studied - it's a segment of the network that's under a common administrative control. 

An area is a logical segment of the network that is composed of contiguous routers and their connecting data links.  

These are logical entities,  but there are two physical bodies as well.    An End System (ES) is a host device; an Intermediate System (IS) is a router.  Not a group of routers, a single router.

The next two parts of this tutorial are listed below in their recommended order of reading:

BSCI Tutorial: ISIS Router Types

BSCI Tutorial: ISIS Hello Types

I'll be posting more ISIS tutorials in March to help you pass this challenging exam, so bookmark the BSCI Exam Resource Page and visit every day for new study material!

Earn Your CCNP With The Personal Guarantee Of Chris Bryant, CCIE #12933:

“I GUARANTEE You'll Pass The Current CCNP Exams - BSCI, ONT, ISCW, and BCMSN - Before The July 31, 2010 Cutoff Date With My CCNP Study Packages ...

... And If You Don't Pass FOR ANY REASON Before That Time, I'll Give You a 100% Free CCNP Study Package Download For The New Exam Track!"

You Also Get A FREE CCNA Security Study Package, Valued at $67, With The Purchase Of Any CCNP Study Package!

Question 3:

BGP synchronization can be safely turned off in which of the following situations?

A. The AS is not a transit AS.

B. Only the DR is running BGP.

C. All routers in the AS are running BGP.

D. When a physical full mesh exists in the AS.

E. When both the DR and BDR are running BGP.

F. When the AS is a transit AS.

Question 4:

Which of the following is true regarding iBGP neighbors?

A. They do not advertise routes learned from one iBGP neighbor to another iBGP neighbor.

B. They must be physically connected.

C. They must be in the same AS.

D. They must use their loopback addresses to form the peer connection.

Question 5:

You have summarized routes in your BGP AS with the command aggregate address 10.8.0.0 255.248.0.0. What should you expect to see in the other routers' BGP tables?

A. The summary route only.

B. None, since this command is incorrectly used (a summary mask cannot be configured).

C. None, since the aggregator command is the correct one to use here.

D. The summary route and the routes being summarized.

E. Since the command is being used incorrectly, the routes will show up the same as before the attempted summarization.

 

The answers await you at the bottom of the page!

 

Earn Your CCNP With The Personal Guarantee Of Chris Bryant, CCIE #12933:

“I GUARANTEE You'll Pass The Current CCNP Exams - BSCI, ONT, ISCW, and BCMSN - Before The July 31, 2010 Cutoff Date With My CCNP Study Packages ...

... And If You Don't Pass FOR ANY REASON Before That Time, I'll Give You a 100% Free CCNP Study Package Download For The New Exam Track!"

You Also Get A FREE CCNA Security Study Package, Valued at $67, With The Purchase Of Any CCNP Study Package!