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Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
01-13-2019, 11:12 PM
Post: #1
When you're studying for the BSCI test on the way to making your CCNP certification, you have surely got to master the usage of BGP attributes. These features permit you to adjust the path or paths that BGP will use to reach certain destination when numerous paths to that destination exist.

In this free BGP training, we're planning to take a peek in the NEXT_HOP credit. You may be thinking "hey, how complicated could this characteristic be?" It's not to 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 attain a destination. Within the following example, R1 is a hub switch and R3 and R2 are spokes. All three routers come in BGP AS 100, with R1 having a relationship with both R2 and R3. There is no BGP peering between R2 and R3.

R3 is advertising the community 33.3.0.0 /24 via BGP, and the value of the credit on R1 is the IP address on R3 that's found in the peer relationship, 172.12.123.3. If you are concerned with food, you will certainly require to discover about clicky. Be taught supplementary info about NSEW > NEWS - Discount Life Insurance Will Give You The Best Protection You Need 1 by going to our dazzling URL.

The problem with the feature comes in if the route is advertised to BGP peers. If R3 were in a separate AS from R1 and R2, the route would be then advertised by R1 to R2 with the next-hop attribute set to 172.12.123.3. The value is kept, when a BGP speaker advertises an approach to iBGP friends which was actually learned from an eBGP expert. This fine linklicious.me coupon URL has limitless refreshing aids for when to acknowledge this enterprise.

Here, all three routers are in AS 100. What will the next-hop attribute be set to when R1 advertises the path to its iBGP friend R2?

R2#show ip address bgp

< no production >

There will be no capability for the route on R2, because the route won't look on R2. By default, a route will not be advertised by a BGP speaker to iBGP neighbors when the route was learned from another iBGP friend.

Fortunately for us, there are several ways around this principle. The most frequent is the use of route reflectors, and we'll look at RRs in the next free BGP tutorial..
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