CCNP Tutorial For The BSCI Exam
Illustrated Exam Review: ISIS
Vital Reading And Watching For All Cisco Certification Candidates:
The July 2010 CCNP Changes (And How To Beat Them!)
To help you beat the July 31, 2010 deadline for the demanding CCNP BSCI exam (and this exam does count on the new track, too!), here's a review of the "high points" of ISIS.
I strongly recommend you visit our BSCI Tutorials and CCNP Practice Exam pages, where you'll find quite a few fully-illustrated ISIS tutorials and practice exams to help you prepare for exam success.
While you're there, be sure to check out our CCNP Guaranteed Pass offer, and enjoy this review!
Chris Bryant
CCIE #12999
"The Computer Certification Bulldog"
chris@thebryantadvantage.com
 
ISIS terms may sound familiar, but their meanings are a bit different than when used with other protocols and operating systems:
Domain: section of the network under common administrative control
Area: logical segment of the network composed of contiguous routers and their data links
Intermediate System: A router.
End System: A host device.
The four levels of ISIS routing:
Level 0: ES-IS routing in the same subnet.
Level 1: IS-IS routing in the same area.
Level 2: IS-IS routing in the same domain.
Level 3: Inter-domain routing performed by InterDomain Routing Protocol (IDRP).
ISIS Router Types And Adjacency Possibilities:
L1 : Can form adjacency with any L1 in the same area and any L1/L2 in the same area.
L2 : Can form adjacency with any L2 in any area, and with an L1/L2 in any area.
L1/L2 : Can form adjacency with any L1 in the same area, L1/L2 in any area, and L2 in any area.
ISIS Hello Types:
ESH: ES Hello – Sent by End Systems to discover a router.
ISH: IS Hello – Sent by Intermediate Systems to announce their presence. End Systems listen for these.
IIH: IS-to-IS Hello – Send by one IS to be heard by another IS. These hellos makes IS-IS adjacencies possible.
Sequence Number Packet types:
CSNP: Complete SNP. Contains complete list of all link state packets from a router's database. Using CSNPs assures that every router on the segment has the latest information.
PSNP: Partial SNP. Request for an LSP, or an ack that a requested LSP has been received.
A router interface's SNPA (Subnetwork Point Of Attachment) is its highest DLCI number if it's on a Frame network, and its MAC address if the interface is on an Ethernet segment.
In a NET address such as 49.0001.1223.1213.1233.00, the “00” is the NSEL field. The six bytes next to that are the System ID. The remaining value is the Area ID.
00 = NSEL
1234.1234.1233 = System ID
49.0001 = Area ID. (Not all Area Ids are this length!)
Rules O'Plenty ...
The Area ID must be two numbers long. "7" is not a valid Area ID, but "17" is.
If the NSEL value is "00", the address is a NET address.
Just as there are private IP addresses, there are private NSAP addresses. Any address beginning with "49" is considered a private address and should not be advertised outside your internal network.
There is no "domain" portion in an NSAP address, which is why ISIS doesn't perform OSI Layer 3 routing. That is handled by the InterDomain Routing Protocol (IRDP).
Every L2 router must have a System ID that is not duplicated anywhere in the domain.
Every L1 router must have a System ID that is not duplicated anywhere in its area.
All routers in an area must have the same Area ID.
The ISIS backbone is a contiguous collection of L2 and/or L1/L2 routers. The ISIS backbone is not assigned a number, as the OSPF backbone is.
After configuring the ISIS process with a NET address, the interface(s) running ISIS must be configured with ip router isis. A typical configuration:
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
To verify adjacencies, run show clns neighbors.
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
ISIS allows route summarization with the summary-address command.
R5(config)#router isis
R5(config-router)#summary-address 148.0.0.0 252.0.0.0
Visit our BSCI Exam Resource Page for tutorials on ISIS, multicasting, and much more!
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!
The Ultimate CCNA Study Package | The Ultimate CCNA Study Guide |
