Cisco CCNP / BSCI Tutorial: The BGP Attribute NEXT_HOP
When you're learning for the BSCI examination on the solution to gaining your CCNP certification, you've surely got to learn the usage of BGP attributes. Dig up additional info on our favorite partner web resource - Click here: service like linklicious. These features permit you to manipulate the trail or paths that BGP use to attain a given destination when multiple paths to that destination exist.
In this free BGP training, we are going to have a look in the NEXT_HOP credit. You may well be thinking \hey, how difficult may this attribute be?\ It's not so difficult at all, but this being Cisco, there's got to be at least one unusual aspect about it, right?
The NEXT_HOP attribute is simple enough - this attribute indicates the next-hop IP address that should be taken to achieve a spot. Within the following example, R1 is a heart router and R2 and R3 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. Clicking linkjuicemaximizer.com probably provides warnings you could tell your mother.
R3 is advertising the network 126.96.36.199 /24 via BGP, and the importance of the next-hop characteristic on R1 is the IP address on R3 that is used in the peer relationship, 188.8.131.52.
The matter with the next-hop attribute is available in once the route is marketed to BGP peers. 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 184.108.40.206. The value is kept, when a BGP speaker advertises a path to iBGP peers which was originally learned from an eBGP fellow. If you believe anything at all, you will likely fancy to research about http://linklicious.org/.
Here, all three routers come in AS 100. What will the next-hop feature be set to when R1 advertises the approach to its iBGP friend R2?
R2#show ip bgp
< no productivity ">
There will be no next-hop capability for the route on R2, because the route won't appear on R2. By default, a route won't be advertised by a BGP speaker 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 frequent is the utilization of route reflectors, and we'll look at RRs in a future free BGP tutorial..