mediumMultiple Choice
350-401 Practice Question: Which BGP attribute is used as the first…
Which BGP attribute is used as the first tie-breaker when multiple paths are available and the weight is equal?
⚠ Common exam trap
Cisco often tests the order of BGP path selection steps, and the trap here is that candidates confuse the Cisco-proprietary 'weight' attribute (which is checked first) with the standard 'Local Preference' attribute (which is checked second), leading them to incorrectly select AS path length or MED as the next tie-breaker.
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
✓
Local preference
When multiple BGP paths are available for the same prefix, the first tie-breaker after comparing weight (where higher weight is preferred) is Local Preference (Local Pref). Since weight is a Cisco-proprietary attribute that is only locally significant, the next step in the BGP best-path selection algorithm is to compare the Local Preference value, with the highest value being preferred. This makes Local Preference the correct first tie-breaker when weight is equal.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Local preference
Why this is correct
Local preference is the second attribute in Cisco's BGP best-path selection process, immediately after the locally significant weight. Because it is a well-known discretionary attribute, it is advertised among iBGP peers within an AS, allowing a network operator to influence outbound traffic across all routers. A higher local preference means the path is more preferred, so it overrides even a longer AS path.
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AS path length
Why it's wrong here
AS path length is the third BGP attribute considered in the decision process, so it can only be evaluated once local preference ties. This attribute counts the total number of AS hops listed in the path, and Cisco's implementation prefers the shorter AS path because it typically implies fewer transit domains and lower routing overhead. However, its placement in the sequence means it cannot compensate for a higher local preference.
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Origin code
Why it's wrong here
Origin code is reached only after AS path length has been compared, which places it as a tie-breaker for paths that already have equal AS hop counts. The origin code indicates how a route was injected into BGP—IGP, EGP, or incomplete—with IGP preferred over EGP and both preferred over incomplete. This attribute is often overlooked in real-world design because origin codes rarely differentiate routes in modern networks.
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MED
Why it's wrong here
MED (Multi-Exit Discriminator) is a metric used to influence inbound traffic from a neighboring AS, and it is evaluated only if origin codes are tied. It is typically applied on external BGP links and compared only when the paths originate from the same neighboring AS; a lower MED value is preferred. Since it appears after origin, a router first checks weight, local preference, AS path length, and origin before ever considering MED.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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