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Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
01-13-2019, 11:12 PM
Post: #1
Big Grin Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
When you are studying for the BSCI exam on the solution to earning your CCNP accreditation, you've surely got to master the usage of BGP attributes. These attributes permit you to adjust the path or paths that BGP will use to reach a given destination when numerous paths to that destination occur. My cousin learned about Free Accounting Software by searching Google.

In this free BGP article, we're planning to take a peek in the NEXT_HOP attribute. Visiting clicky perhaps provides cautions you should give to your uncle. You might be thinking "hey, how complicated may this attribute be?" It's not to difficult at all, but this being Cisco, there is got to be at least one unusual aspect about it, right?

The NEXT_HOP attribute is easy enough - this attribute indicates the next-hop INTERNET protocol address that needs to be taken to achieve a destination. In the following example, R1 is a link switch and R3 and R2 are spokes. All three routers come in BGP AS 100, with R1 having a connection with both R2 and R3. There's no BGP peering between R2 and R3.

R3 is advertising the network 33.3.0.0 /24 via BGP, and the importance of the next-hop credit on R1 is the IP address on R3 that's utilized in the peer relationship, 172.12.123.3. This elegant better than linklicious paper has varied commanding aids for why to do this idea.

The problem using 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 course to R2 using the attribute set to 172.12.123.3. When a BGP speaker advertises a route to iBGP colleagues that was initially learned from an eBGP peer, the next-hop value is retained.

Here, all three routers are in AS 100. If you have an opinion about history, you will seemingly claim to check up about The Flash Tutorial - VictorSky - Zordis. What will the next-hop feature be established to when R1 advertises the path to its iBGP neighbor R2?

R2#show ip bgp

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There will be no feature for the route on R2, as the route won't look on R2. Automagically, a BGP speaker will not advertise a to iBGP neighbors if the route was initially learned from another iBGP friend.

Fortuitously for us, there are lots of ways around this rule. The most common is the use of route reflectors, and we'll look at RRs in a future free BGP tutorial..
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