This article outlines an issue reported by an FIA (Fiber Internet Access)customer, where their traffic is predominantly routed through their secondary provider instead of the intended primary provider. The root cause was identified as a routing preference behavior—prefixes learned from FIA customers were not preferred over those received from directly connected eBGP peers.
[email protected]_Router> show route XXX.XXX.120.0/24 extensive | match "source|inactive|Localpref"
Source: XX.XX.54.235 << Primary RR
Localpref: 270
Source: XX.XX.54.234 << Secondary RR
Inactive reason: Not Best in its group - IGP metric
Source: XXX.XXX.70.194 << FIA eBGP Peer
Inactive reason: Local Preference
Localpref: 100
The FIA customer is connected to two upstream providers: A primary provider (Juniper customer) and a secondary provider (non-Juniper customer). The FIA customer is advertising their prefixes to the Internet through both upstream connections.
Upon investigation, we observed that the Provider Edge (PE) router—where the FIA customer is connected—is receiving the same prefixes via two paths:
However, the directly received eBGP route from the customer is marked as inactive. This is due to a higher local preference being set on the route received from the Route Reflector. Specifically:
As a result, the PE router prefers the route via the Route Reflector, which leads to traffic being routed through the secondary provider instead of the intended primary provider.
A routing policy was implemented on the PE router to assign a higher local preference (e.g., 280) to routes received directly from the FIA customer. This ensured that the PE router now prefers the direct eBGP path, aligning with the intended routing behavior.