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Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
09-08-2017, 06:37 AM,
#1
Big Grin  Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
When you are studying for the BSCI test on the solution to gaining your CCNP accreditation, you've surely got to master the usage of BGP attributes. These capabilities permit you to manipulate the road or paths that BGP will use to reach a given destination when multiple paths to that destination exist.

Within this free BGP article, we're planning to take a look at the NEXT_HOP attribute. You may be thinking "hey, how difficult could this attribute be?" It is not very difficult at all, but this being Cisco, there's got to be at least one unusual detail about it, right?

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

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

The problem with the attribute will come in when the route is advertised to BGP peers. If R3 were in another AS from R1 and R2, the route would be then advertised by R1 to R2 using the next-hop attribute set to 172.12.123.3. If you have an opinion about protection, you will likely fancy to learn about purchase here. When a BGP speaker advertises a route to iBGP friends that has been initially learned from an eBGP peer, the value is stored.

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

R2#show internet protocol address bgp

< no output >

There will be no credit for the route on R2, because the route will not look on R2. Identify further on our partner portfolio by going to Discount Treadmills Do You Get What You Pay For? 3. By default, a route won't be advertised by a BGP speaker to iBGP neighbors if the route was learned from another iBGP friend.

Fortunately for all of us, there are many ways around this concept. The most frequent is the usage of route reflectors, and we'll look at RRs in the next free BGP article.. To get another way of interpreting this, consider checking out: Vacation Europe Discount Airfare And Spend Less 33.
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