Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP abc

When you're learning for the BSCI examination on the way to getting your CCNP accreditation, you've got to master the use of BGP attributes. These capabilities allow you to manipulate the trail or paths that BGP use to attain a given destination when multiple paths to that destination occur.

In this free BGP article, we're likely to take a peek at the NEXT_HOP credit. You may be thinking "hey, how complicated could this feature be?" It's not very complex at all, but this being Cisco, there is got to be at least one unusual aspect about it, right?

The NEXT_HOP attribute is simple enough - this attribute indicates the next-hop INTERNET protocol address that should be taken to attain a spot. In the following instance, R1 is a centre 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 R3 and R2.

R3 is advertising the community 33.3.0.0 /24 via BGP, and the value of the next-hop credit on R1 is the IP address on R3 that is utilized in the peer relationship, 172.12.123.3. Should people claim to learn new info on linklicious.org, we recommend many on-line databases you could pursue.

The matter using the next-hop credit will come in once the route is advertised to BGP peers. To research more, please consider having a glance at: indexification. If R3 were in a separate AS from R1 and R2, R1 would then advertise the route to R2 using the next-hop attribute set to 172.12.123.3. The next-hop value is kept, whenever a BGP speaker advertises a route to iBGP friends that was initially learned from an eBGP peer.

Here, all three routers are in AS 100. What will the characteristic be established to when R1 advertises the path to its iBGP friend R2?

R2#show internet protocol address bgp

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There will be no next-hop feature for the route on R2, since the route won't appear on R2. By default, a route will not be advertised by a BGP speaker to iBGP neighbors when the route was initially learned from another iBGP friend.

Fortunately for all of us, there are many ways around this rule. The most common is the usage of route reflectors, and we'll look at RRs in the next free BGP guide.. How Linklicious.Me Works includes further about the meaning behind it. Visiting research linklicious.me maybe provides aids you could use with your co-worker.