Cisco CCNP BSCI Certification The BGP Attribute MED
Below is a MRR and PLR article in category Computers Technology -> subcategory Computer Certification.
Cisco CCNP/BSCI Certification: Understanding the BGP MED Attribute
Overview
To conquer the BSCI exam and secure your CCNP certification, mastering BGP attributes is essential. Explore the significance of the MED attribute in this insightful guide by Chris Bryant, CCIE
12933.
Navigating BGP for CCNP Certification
Preparing for the BSCI exam involves diving deep into BGP, a protocol unlike any covered in the CCNA curriculum. One key aspect of BGP is its use of path attributes to prioritize paths when multiple routes are available.
While earlier tutorials covered attributes like "weight" and "local preference" that help choose a path to a destination, MED, or Multi-Exit Discriminator, guides routers on which path to take to reach a network from a different AS.
Utilizing MED in BGP
MED is crucial for informing routers in an external autonomous system (AS) about the preferred pathway to reach a specific network within your AS. For instance, in AS 100, you can configure MED values to signal AS 200 on which route to take to access a network in AS 100.
To adjust the MED, use a route-map, recognizing that there's no direct "set med" command. Instead, alter the path's metric. Suppose AS 200 has two entry paths: 100.1.1.0/24 and 100.2.2.0/24. To prioritize the first, create ACLs to identify both paths:
```plaintext
R1(config)
access-list 22 permit 100.1.1.0 0.0.0.255
R1(config)access-list 23 permit 100.2.2.0 0.0.0.255
```Next, implement a route-map to assign a lower metric to the preferred path:
```plaintext
R1(config)
route-map PREFER_PATH permit 10
R1(config-route-map)match ip address 22
R1(config-route-map)set metric 100
R1(config-route-map)route-map PREFER_PATH permit 20
R1(config-route-map)match ip address 23
R1(config-route-map)set metric 250
```Finally, apply this route-map to the relevant neighbor:
```plaintext
R1(config-route-map)
router bgp 100
R1(config-router)neighbor 22.2.2.2 route-map PREFER_PATH out
```Key Takeaways
Remember, while many BGP attributes favor higher values, MED functions as an external metric?"a lower value is preferred, similar to protocols covered in your CCNA studies. Embracing this understanding is crucial for passing the BSCI exam and achieving CCNP certification.
You can find the original non-AI version of this article here: Cisco CCNP BSCI Certification The BGP Attribute MED .
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