ANS-C01 Network Design Practice Question

A company is designing a Direct Connect solution with two connections to provide high availability. The company has two customer routers, each connected to a separate AWS Direct Connect location. The company uses BGP to advertise the same prefixes from both routers. What is the correct way to configure the BGP attributes to ensure that traffic uses both connections actively?

⚠ Common exam trap

Candidates often confuse AS path prepending as a method to achieve equal path preference, but prepending actually makes a path longer and less preferred, so using it on both routers would still result in equal but artificially inflated AS path lengths, which is unnecessary and not the standard approach for active/active use.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Advertise the same AS path length from both routers.

Advertising the same AS path length from both routers ensures that AWS Direct Connect routers see both paths as equally preferred under the BGP path selection process (which considers AS path length before MED, local preference, and IGP metric). With equal AS path length, traffic will be load-balanced across both Direct Connect connections, actively using both links for inbound traffic from AWS to the customer network.

Answer analysis

Option-by-option breakdown

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

✓
Advertise the same AS path length from both routers.
Why this is correct
Equal AS path length results in equal preference, allowing active-active use.
✗
Use AS path prepending on both routers to make the paths equally long.
Why it's wrong here
Prepending is normally used to lengthen one path relative to the other so it becomes less preferred — using it to make both paths artificially equal just reproduces the same relative preference that already exists with the natural, unprepended AS-path, so it changes nothing about BGP's path-selection outcome while adding configuration to maintain.
✗
Set a higher local preference on the primary router and lower on the secondary.
Why it's wrong here
This makes the primary route more preferred, not active-active.
✗
Advertise a shorter AS path on the primary router and a longer AS path on the secondary router.
Why it's wrong here
This makes the primary path more preferred, not active-active.

Go deeper

ANS-C01 Network Design Practice Question

Why each option matters

Option-by-option breakdown

Related to this question