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Symptoms: Traffic From Specific Source Not Taking Expected Path

  • Traffic from the 10.100.0.0/24 subnet should route through ISP-B (secondary link) per policy, but it is using ISP-A (primary link) instead.
  • Policy-based routing was configured to send 10.100.0.0/24 traffic via a dedicated WAN link for compliance reasons.
  • Traceroute from a host on 10.100.0.0/24 shows the traffic taking the ISP-A path.
  • Traffic from all other subnets correctly routes via ISP-A as expected.
  • The policy route was configured last week but has apparently never worked.
  • Both ISP links are up and functioning; failover between them works for normal traffic.
  • The router shows the route-map is applied to an interface, but traffic still takes the default route.
  • No errors in router logs related to policy routing.