CCNP Practice Question: An enterprise network has two routers, R1 and R2,…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Set a higher local preference on R1 for the default route learned from ISP1.

  Why this is correct

  Setting a higher local preference on R1 for the default advertisement from ISP1 is correct because local preference is the first major BGP attribute used to choose the outbound path (after weight) and is propagated to iBGP peers. By assigning this route a higher local preference, R1 will prefer its directly received default from ISP1 over the alternate default route learned from R2, and that preference will also be advertised to R2 via iBGP, making ISP1 the primary egress for the entire AS. Local preference is evaluated before AS_PATH, MED, and IGP cost, so it is the most direct and scalable way to control outbound traffic policy.

• ✗

  Set a lower MED on R1 for the default route learned from ISP1.

  Why it's wrong here

  Lowering MED on the default route learned from ISP1 is incorrect because the MED attribute is a signaling mechanism used by one AS to tell an external AS how to reach its prefixes—it influences inbound traffic, not outbound. When R1 sets a lower MED on the route it advertises to ISP1, ISP1 will use that metric to prefer this entry point into the enterprise, but it has no bearing on how R1 itself selects a default route. Furthermore, MED is only compared among routes received from the same neighboring AS unless aggressive always-compare-med is configured, and it always loses to local preference anyway, so this change cannot affect R1's egress selection.

• ✗

  Prepend AS 65000 multiple times on R2's updates to ISP2.

  Why it's wrong here

  Prepending AS 65000 multiple times on R2's updates to ISP2 lengthens the AS_PATH of the enterprise's advertised networks, making those routes look less desirable to ISP2 and its downstream peers. This is purely an inbound traffic-engineering action: it encourages traffic from the internet to enter via ISP1 instead of ISP2, based on the longer AS path seen by remote ASes. It does not alter the default route that R2 has received from ISP2, nor does it influence how R2 or R1 chooses an eBGP best path for outbound internet traffic, because AS_PATH is an attribute of routes sent to neighbors, not something applied to routes the local AS has imported.

• ✗

  Configure a community on R1 to mark the default route as no-export.

  Why it's wrong here

  Configuring the no-export community on R1's default route learned from ISP1 would only prevent that route from being re-advertised to any eBGP neighbor outside the local AS—it does not modify any BGP path-selection attribute. Since the route was already received from ISP1, tagging it no-export restricts propagation to other external peers, but has no impact on R1's best-path decision or on the preference of ISP1 over ISP2 for outbound traffic. BGP communities like no-export are route-delivery policy tools, not selection metrics; they control where a route may be advertised, whereas local preference determines which route is chosen when forwarding packets.