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Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP

When you're studying for the BSCI examination on the way to making your CCNP accreditation, you've surely got to learn the usage of BGP attributes. These capabilities allow you to change the road or paths that BGP will use to reach a given destination when numerous paths to that destination exist.

Within this free BGP article, we are planning to have a look in the NEXT_HOP attribute. You might be thinking \hey, how complicated can this feature be?\ It's not so complex at all, but this being Cisco, there is 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 reach a spot. In the event you fancy to learn further about the guide to linklicious.me, there are heaps of online resources you might investigate. Within the following example, R1 is a center modem and R3 and R2 are spokes. All three routers are in BGP AS 100, with R1 having a connection with both R3 and R2. Linklicious Tutorial is a tasteful online library for new info about the reason for it. 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 feature on R1 is the IP address on R3 that's found in the peer relationship, 172.12.123.3.

The problem with the credit is available in when the route is advertised to BGP peers. Be taught more about linklicious.me alternatives by browsing our telling wiki. If R3 were in another AS from R1 and R2, the route would be then advertised by R1 to R2 using the attribute set to 172.12.123.3. When a BGP speaker advertises a route to iBGP colleagues that was originally learned from an eBGP fellow, the value is kept.

Here, all three routers come in AS 100. What'll the next-hop attribute be established to when R1 advertises the route to its iBGP friend R2?

R2#show internet protocol address bgp

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There will be no next-hop attribute for the route on R2, because the route won't look on R2. Visiting linklicious.me affiliate certainly provides tips you could give to your dad. Automagically, a BGP speaker won't advertise a to iBGP neighbors if the route was first learned from another iBGP neighbor.

Luckily for us, there are numerous ways around this principle. The most typical is using route reflectors, and we'll look at RRs in a future free BGP article..