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,...