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Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
04-17-2018, 06:33 PM
Post: #1
Big Grin Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
When you are learning for the BSCI test on the way to earning your CCNP accreditation, you have surely got to learn the usage of BGP attributes. These attributes permit you to manipulate the trail or paths that BGP uses to attain a given destination when multiple paths to that destination occur.

Within this free BGP tutorial, we are planning to take a peek in the NEXT_HOP characteristic. Maybe you are thinking "hey, how complicated may this attribute be?" It is not so 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 straightforward enough - this attribute indicates the next-hop IP address that needs to be taken to achieve a destination. In the following instance, R1 is a center router and R2 and R3 are spokes. All three routers are in BGP AS 100, with R1 having a relationship with both R3 and R2. There is no BGP peering between R2 and R3.

R3 is advertising the community 33.3.0.0 /24 via BGP, and the importance of the feature on R1 is the IP on R3 that's utilized in the peer relationship, 172.12.123.3. To learn additional information, consider checking out: site preview.

The problem with the next-hop feature will come in if the route is marketed to BGP peers. If R3 were in a different AS from R1 and R2, R1 would then advertise the route to R2 using the attribute set to 172.12.123.3. When a BGP speaker advertises a route to iBGP peers that has been actually learned from an eBGP look, the value is stored.

Here, all three routers are in AS 100. What'll the next-hop characteristic be established to when R1 advertises the approach to its iBGP neighbor R2?

R2#show ip address bgp

< no output >

There will be no attribute for the route on R2, since the route will not look on R2. Automatically, a route will not be advertised by a BGP speaker to iBGP neighbors when the route was first learned from another iBGP neighbor. Learn extra info on our favorite related website - Click this website: Entertainment Promotion Book Register 38847.

Fortunately for all of us, there are numerous ways around this concept. Be taught more on this affiliated website - Click here: follow us on twitter. The most frequent is the utilization of route reflectors, and we'll look at RRs in the next free BGP guide..
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