This is a clone of issue OCPBUGS-56506. The following is the description of the original issue:
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Description of problem:

There is a incompatibility with route handling of BGP advertised UDN network host subnets.

For example, two UDN L3 networks netA (10.165.0.0/16) and netB (10.166.0.0/16) are created.

node-1 and node-2 are assigned with host subnets as like below.

node-1:

net-A 10.165.1.0/24
net-B 10.166.1.0/24

node-2:
net-A 10.165.2.0/24
net-B 10.166.2.0/24

The ovnkube-node pod on each node learns remote routes, imports into its FRR instance and corresponding ip route rules are created.

node-1:
10.165.2.0/24 nhid 57 via 172.18.0.3 dev breth0 proto bgp metric 20 
10.166.2.0/24 nhid 57 via 172.18.0.3 dev breth0 proto bgp metric 20 
node-2:
10.165.1.0/24 nhid 54 via 172.18.0.2 dev breth0 proto bgp metric 20 
10.166.1.0/24 nhid 54 via 172.18.0.2 dev breth0 proto bgp metric 20

The correct behavior would be avoid importing these routes into FRR so that inter UDN traffic egress into provider network by default, it provides flexibility for provider network to define routing rules among these networks.

The host subnets assigned on the same node is not imported, so pod-pod traffic on netA and netB networks within same node egressing into provider network. so we need similar behavior for remote routes as well.

Slack discussion: https://redhat-internal.slack.com/archives/C07AT0XP4J0/p1747667324516379

Version-Release number of selected component (if applicable):

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Affected Platforms:

Is it an

1. internal CI failure
2. customer issue / SD
3. internal RedHat testing failure

If it is an internal RedHat testing failure:

• Please share a kubeconfig or creds to a live cluster for the assignee to debug/troubleshoot along with reproducer steps (specially if it's a telco use case like ICNI, secondary bridges or BM+kubevirt).

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• If it's a connectivity issue,
• What is the srcNode, srcIP and srcNamespace and srcPodName?
• What is the dstNode, dstIP and dstNamespace and dstPodName?
• What is the traffic path? (examples: pod2pod? pod2external?, pod2svc? pod2Node? etc)

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  • If it is a connectivity issue:
    • What is the srcNode, srcNamespace, srcPodName and srcPodIP?
    • What is the dstNode, dstNamespace, dstPodName and dstPodIP?
    • What is the traffic path? (examples: pod2pod? pod2external?, pod2svc? pod2Node? etc)
    • Please provide the UTC timestamp networking outage window from must-gather
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  • If it is not a connectivity issue:
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