Showing posts with label next. Show all posts
Showing posts with label next. Show all posts

Saturday, December 27, 2008

What Certification Should You Pursue After The CCNA ?

Once you've got your CCNA, you're ready to move on to the next level, the Professional certifications. For years, Cisco had one Professional certification, the Cisco Certified Network Professional (CCNP) certification. Over time, Cisco has expanded this level of certifications to include the Cisco Certified Security Professional (CCSP) and Cisco Certified Voice Professional (CCVP).

With security and voice being the two most rapidly expanding areas of today's networks, some new CCNAs consider going after the CCSP or CCVP without first adding the CCNP to their resume.

While it's temping to hurry up and get a Cisco security or voice certification, the best thing you can do for your networking career is achieve your CCNP certification first, then decide on the CCVP or CCSP.

Why? Because the CCNA is just the tip of a very large iceberg when it comes to routing and switching. It's a very important accomplishment, and the CCNA is indeed the foundation of your networking career, but you need to add on to that level of understanding routing and switching before moving on to more specialized areas.

Two examples are OSPF and BGP. You learn about the theory of OSPF and some basic and intermediate configurations of that protocol in your CCNA studies, but the knowledge you acquire of OSPF in your CCNP studies is invaluable. As for BGP, there is no BGP in the CCNA curriculum, but it is a great idea to have some BGP knowledge in today's networks. It's also good for your career.

I know it is a huge temptation to go after the security and voice certifications while not paying attention to the CCNP. Do yourself a huge favor and add the tremendous amount of routing and switching knowledge needed for the CCNP to your knowledgebase, and you can then move on to the CCSP or CCVP. Even better, you'll be better prepared to climb the biggest certification mountain around - the CCIE!

Thursday, December 25, 2008

Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP

When you're studying for the BSCI exam on the way to earning your CCNP certification, you've got to master the use of BGP attributes. These attributes allow you to manipulate the path or paths that BGP will use to reach a given destination when multiple paths to that destination exist.

In this free BGP tutorial, we're going to take a look at the NEXT_HOP attribute. You may be thinking "hey, how complicated can this attribute be?" It's not very complicated at all, but this being Cisco, there's got to be at least one unusual detail about it, right?

The NEXT_HOP attribute is simple enough - this attribute indicates the next-hop IP address that should be taken to reach a destination. In the following example, R1 is a hub router and R2 and R3 are spokes. All three routers are in BGP AS 100, with R1 having a peer relationship with both R2 and R3. There is no BGP peering between R2 and R3.

R3 is advertising the network 33.3.0.0 /24 via BGP, and the value of the next-hop attribute on R1 is the IP address on R3 that is used in the peer relationship, 172.12.123.3.

The issue with the next-hop attribute comes in when the route is advertised to BGP peers. If R3 were in a separate AS from R1 and R2, R1 would then advertise the route to R2 with the next-hop attribute set to 172.12.123.3. When a BGP speaker advertises a route to iBGP peers that was originally learned from an eBGP peer, the next-hop value is retained.

Here, all three routers are in AS 100. What will the next-hop attribute be set to when R1 advertises the route to its iBGP neighbor R2?

R2#show ip bgp

< no output >

There will be no next-hop attribute for the route on R2, because the route will not appear on R2. By default, a BGP speaker will not advertise a route to iBGP neighbors if the route was first learned from another iBGP neighbor.

Luckily for us, there are several ways around this rule. The most common is the use of route reflectors, and we'll look at RRs in a future free BGP tutorial.