I just got back from… umm.. working, and checked my blog feeds for some news about the IE announcements. I had thought about registering for the webcast but thought better to wait until someone feeds me the info instead.

So thanks to CCIE Pursuit and CCIE Journey for being the first few to alert me of the details of the announcements.

I’m happy to see that even though I missed the webcast, IE has the recording of the juicy details available for your viewing pleasure. I’m excited because I hear they will venture out to younglins like us who are just starting out in the world of Cisco by encompassing a CCNx training program as well. I would think it would make a good transition from CCNP to CCIE track in terms of training – that is if you prefer InternetworkExpert as a training vendor of choice. I’m feeling that IE is recognizing that there are people out there that are just as serious in their pursuit to gain their CCNP certs as much as there are serious candidates vying for their CCIE. Hopefully this would be a good thing for us CCNP candidates as it is for IE in terms of capturing more interested audience for using their products. In the end more customers for them, and better, more high-quality level of training for us.

Integrated IS-IS in a CLNS Environment

• A fundamenatl difference between NET address and IP address:
  • NET address identifies a device (an IS or ES)
  • IP address identifies the interface
• Each IS-IS router must have a NET address configured even if Integrate IS-IS is only used for IP routing only.
  • Integrated IS-IS relies on the support of CLNS routing.
  • The OSI protocols (such us hello PDUs) are used to form neighbor relationship between routers and,
  • SPF calculations rely on a configured NET address to identify the routers.
• Default routes are injected into an area by L1/L2 routers. This allows packets to be forwarded to destination areas different from the area where the packets originated.
• When routing IP traffic using IS-IS, IP subnets are treated like leaf objects associated with IS-IS areas.
  • The router looks up the destination network in its routing table.
  • If traffic belongs to a different area, it is forwarded to the nearest L1/L2 router.
• Route summarization allows scalability by minimizing the size of teh LSDB and routing tables, the amount of processing, and the number of network updates.

OSI Routing Table

• IS-IS uses an OSI forwarding database (routing table) to select the best path to a destination.
• To determine best path, IS-IS routers use SPF to calculate the SPF tree to OSI destinations (NETs) based on the information in the LSDB.
• Routers may run the SPF algorithm twice (one for each level) and create separate SPF trees for each level.
• Routers insert the best paths in the CLNS routing table (aka OSI forwarding database).
• Routers calculate ES reachability with a partial route calculation (PRC), based on the L1 and L2 SPF trees.

IP Routing Table

• IP Routes only require PRC.
• Integrate IS-IS includes IP reachability infromation in the LSPs, treating it as if it were ES information.
  • In other words IP prefix information is treated as leaf connections to the SPF tree.
  • Therefore, updating IP reachability requires only a PRC, similar to ES reachability in an OSI network.
• The PRC generates best-path choices for IP routes and offers the routes to the IP routing table.
• When IP routes are entered into the routing table, they are shown as via L1 or L2 appropriately.

Integrated IS-IS Configuration

The following four steps outline the process to setup Integrated IS-IS:

1. Define the Area and Addressing
   • CLNS addresess must be planned for a two-level hierarchy. This is to allow for interarea traffic to traverse the L2 backbone area.
   • IP addressing must allow for address summarization to benefit from scalability and a hierarchical design.
2. Enable IS-IS on the Router
   • Use the global command:

     router isis [area-tag]

     • The optional area tag identifies multiple IS-IS process.
     • If ommitted, it assumes a tag of 0.
   • IP routing is enabled by default.
   • CLNS routing is disabled by default.
   • You can enable CLNS routing using the clns routing global configuration command.
     • You must enable CLNS routing at each interface if using it at all.
3. Configure the NET
   • To assign the NET to the router, use the following router configuration command:
     • net network-entity-title
   • Even when using IS-IS for IP only, a NET must still be configured.
   • The NET consists of:
     • Area address – between 1 and 13 bytes in length.
     • System ID – fixed length of 6 bytes in Cisco routers.
     • NSEL of value 00.
4. Enable IS-IS on Interfaces
   • Determine which interfaces will participate in IS-IS.
   • Once the interfaces that will use IS-IS to route IP has been determined, use the following interface configuration command to enable IS-IS on that interface:

     ip router isis [area-tag]

     • The area-tag field identifies the IS-IS process to be enabled.
     • If there is no area-tag configured, IOS will assume a value of 0.
   • Make sure to also configure interfaces to stub IP network, such as loopback interfaces.
   • Use the clns router isis [area-tag] interface configuration command to enable the IS-IS routing process on an interface to support CLNS routing.

Optimizing IS-IS

• IS-IS default configuration leaves the router with an IS type of L1/L2, by default.
• Each router should be configured to support the minimum level of routing required.
  • If a router only requires to operate as an internal router, there is no use to leave it as an L1/L2 router. It makes more sense to configure it as an L1 router.

Changing IS-IS Router Level

• If a router is to operate as an internal area router only, use the following router configuration command

is-type level-1

• If a router will act only as a backbone router, use the following router configuration command:

is-type level-2-only

• If the level type has been changed from the default, you can return to the default with the following router configuration command:

is-type level-1-2

Changing the IS-IS Interface Level

• A router that functions as an L1/L2 router does not always have to establish both types of adjacencies over all interfaces. Sometimes an L1/L2 router may be connected to another router that is configured as an L1 router only, or vice versa, another router configured as L2 only.
• To make IS-IS more efficient, it is good practice to configure the interface to only send the needed type of hellos that the other router on the other end is expecting.
• To configure the interface to send only a specific type of hello, use the following interface configuration command:

isis circuit-type {level-1 | level-1-2 | level-2-only}

• Depending on what level you configure, the router will send only hellos appropriate for that level.
• The default is level-1-2
  • Meaning the router will attempt to establish both types of adjacencies over the interface.

Changing the IS-IS Metric

• All interfaces in an IS-IS have a metric value of 10 by default.
• Unlike most other IP protocols, IS-IS on a Cisco router does not take into account line speed or bandwidth when it sets its link metrics.
• Leaving the metric to its default value can result in suboptimal routing in networks with links of varying speed.
• To change the metric value, use the following interface configuration command:

isis metric metric [delay-metric [expense-metric [error-metric]]] {level-1 | level-2]

• The metric can have different values for L1 and L2 over the same interface.
• The metric value is anywhere from 1 to 63.
• IS-IS defines four different types of metrics:
  • Cost (default)
  • Delay (optional) – measures transit delay.
  • Expense (optional) – measures monetary cost of link utilization.
  • Error (optional) – measures the residual error probability associated with the link.
• The metric value for all IS-IS interfaces can be changed all at once using the following router configuration command:

metric default-value {level-1 | level-2}

• If the keyword level-1 or level-2 is not used, the metric will be applied to both L1 and L2 interfaces.
  • This command is only availablee in Cisco IOS 12.3(4)T and later.
  • It only supports cost metric.

Figure 1: IS-IS Configuration Example

• There are two router in area 49.0001: R1 and R2.
• R1 is strictly an L1 router.
  • It makes sense to configure is with is-type level-1 router since it will only function as an L1.
  • Configuring the interface with isis circuit-type level-1 ensures that it only passes L1 hellos.
• R2 has two functions therefore it is left with the default setting of an L1/L2 router type.
  • Fa0/0 is configured with circuit type L1 because it connects to only an L1 router. It will only exchange L1 hellos.
  • Similarly, S0/0/1 interface connects only to an L2 router, so the circuit type is configured as an L2.
• R3 in area 49.0002 has only one router and only does L2 routing.
  • It should then be configured as L2-only IS type and the interface with L2 circuit type.

IP Route Summarization in IS-IS

Benefits of summarization are:

• Reduced routing table size
• Reduced LSP traffic and protection from flapping routes
• Reduced memory requirements
• Reduced CPU usage
• A more stable network because topology changes can be isolated

To configure route summarization is IS-IS, use the following router configuration command:

summary-address address-mask [level-1 | level-2 | level-1-2] [tag tag-number] [metric metric-value]

• This command can be used on any router in an IS-IS network.
• The router summarizes IP routes int L1, L2, or both.
  • The default is into L2 (level-2).
• The optional tag-number is used to tag the summary route.
• The optional metric-value is applied to the summary route.

On our way to work this morning, the sun had barely touched the horizon and it brought with it an awesome collage of purple, orange, yellow, and pink.

After my wife dropped me off to work, she and our two-year old drove further west so she can drop him off to his grandma’s, and she to get her first-grade classroom ready for the day. As they were driving towards their destination, the sky started to paint an even brighter and colorful picture – complete with puffy, feathery clouds embossed in purple and gray lining, and swirlying colors of orange and yellow.  It is the same scence I’m looking at while standing by the huge glass window in the office. I then get a call from my wife and she describes as verbatim as she could how my two-year old son described what he saw:

“Wow, dats byuuutifulll!”

“The sun painted the sky.”

“The sun is the illoostrater*”

A simple observation from a two-year old, but yet the novelty of a beautiful morning skyline still amazes them. Nowadays, grownups like myself rarely look up and just let ourselves be amazed by such simple (and at the same time complex) things.

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*Illustrator: it’s our nightly routine to read to our son before he goes to sleep. He usually goes through about 5 or so children’s book before he is satisfied. He has learned that the author is “the one who writes the book” and the illustrator is the “one who draws the cool pictures”.