Hello @menning777
It is likely caused by a blackholing effect due to the more specific /24 null route. When both the /23 and /24 null routes exist, the router prioritizes the more specific /24 route, meaning all traffic destined for 103.246.86.0/24 is dropped immediately, even if a valid route exists elsewhere.
This could explain why traffic to global websites like Yahoo fails while local traffic remains unaffected. Once you remove the /24 null route, only the /23 route remains, which acts as a safety net and drops traffic only if no better route exists, allowing global traffic to flow correctly.
So, you should keep the /23 null route but avoid configuring the /24 unless absolutely necessary.
Why now this issue ?
This problem may have surfaced recently due to changes in routing behavior, such as a BGP update, overlapping advertisements, or a shift in return traffic paths. If your network is advertising 103.246.86.0/24 but simultaneously blackholing it, inbound traffic from the internet may be lost. Additionally, any recent policy changes or ACL modifications could be influencing how your router handles traffic.
Best regards
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