Description of problem: [BGP UDN pre-merge testing] in eBGP mode, UDN is not advertised 20 minutes after UDN RA was accepted 

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

How reproducible:

Steps to Reproduce:

1. Configured BGP in eBGP mode, and with default network successfully advertised, created a UDN namespace, and L3 UDN in the namespace, label the UDN with label app=udn that used in ra-udn.yaml

#oc get userdefinednetwork -A
NAMESPACE                                NAME                AGE
e2e-test-udn-networking-8w3qt3q0-kw4fm   udn-network-78349   56s

#oc get userdefinednetwork udn-network-78349 -n e2e-test-udn-networking-8w3qt3q0-kw4fm --show-labels
NAME                AGE   LABELS
udn-network-78349   71s   app=udn

#oc get userdefinednetwork udn-network-78349 -n e2e-test-udn-networking-8w3qt3q0-kw4fm -oyaml
apiVersion: k8s.ovn.org/v1
kind: UserDefinedNetwork
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"k8s.ovn.org/v1","kind":"UserDefinedNetwork","metadata":{"annotations":{},"name":"udn-network-78349","namespace":"e2e-test-udn-networking-8w3qt3q0-kw4fm"},"spec":{"layer3":{"mtu":1400,"role":"Primary","subnets":[

]},"topology":"Layer3"}}
  creationTimestamp: "2025-03-08T23:28:55Z"
  finalizers:
  - k8s.ovn.org/user-defined-network-protection
  generation: 1
  labels:
    app: udn
  name: udn-network-78349
  namespace: e2e-test-udn-networking-8w3qt3q0-kw4fm
  resourceVersion: "232212"
  uid: a2697b46-725f-45e0-9eb8-fc8f86bc7c63
spec:
  layer3:
    mtu: 1400
    role: Primary
    subnets:
    - cidr: 10.150.0.0/16
      hostSubnet: 24
  topology: Layer3
status:
  conditions:
  - lastTransitionTime: "2025-03-08T23:28:55Z"
    message: NetworkAttachmentDefinition has been created
    reason: NetworkAttachmentDefinitionCreated
    status: "True"
    type: NetworkCreated
  - lastTransitionTime: "2025-03-08T23:28:55Z"
    message: Network allocation succeeded for all synced nodes.
    reason: NetworkAllocationSucceeded
    status: "True"
    type: NetworkAllocationSucceeded

2. Applied a second ra-udn.yaml with networkSelector to select the UDN created in step 1

—
kind: List
apiVersion: v1
metadata: {}
items:

• apiVersion: k8s.ovn.org/v1
    kind: RouteAdvertisements
    metadata:
      name: udn
    spec:
      advertisements:
      - PodNetwork
      - EgressIP
      networkSelector:
        matchLabels:
          app: udn

3. UDN RA was accepted after waiting between 2-3 minutes

#oc get ra -A
NAME      STATUS
default   Accepted
ra-udn    Accepted

4.  After UDN RA is accepted, waited another 12 minutes, UDN was not advertised

#sudo podman exec -it aa60d26fc82b /bin/sh
/ # date; ip route show | grep bgp
Sun Mar  9 16:40:55 UTC 2025
10.128.0.0/23 via 192.168.111.22 dev offloadbm proto bgp metric 20 
10.128.2.0/23 via 192.168.111.23 dev offloadbm proto bgp metric 20 
10.129.0.0/23 via 192.168.111.20 dev offloadbm proto bgp metric 20 
10.129.2.0/23 via 192.168.111.25 dev offloadbm proto bgp metric 20 
10.130.0.0/23 via 192.168.111.21 dev offloadbm proto bgp metric 20 
10.130.2.0/23 via 192.168.111.40 dev offloadbm proto bgp metric 20 
10.131.0.0/23 via 192.168.111.24 dev offloadbm proto bgp metric 20 
10.131.2.0/23 via 192.168.111.47 dev offloadbm proto bgp metric 20

/ # date; ip route show | grep bgp
Sun Mar  9 16:51:26 UTC 2025
10.128.0.0/23 via 192.168.111.22 dev offloadbm proto bgp metric 20 
10.128.2.0/23 via 192.168.111.23 dev offloadbm proto bgp metric 20 
10.129.0.0/23 via 192.168.111.20 dev offloadbm proto bgp metric 20 
10.129.2.0/23 via 192.168.111.25 dev offloadbm proto bgp metric 20 
10.130.0.0/23 via 192.168.111.21 dev offloadbm proto bgp metric 20 
10.130.2.0/23 via 192.168.111.40 dev offloadbm proto bgp metric 20 
10.131.0.0/23 via 192.168.111.24 dev offloadbm proto bgp metric 20 
10.131.2.0/23 via 192.168.111.47 dev offloadbm proto bgp metric 20 

Actual results:  UDN is not advertised with eBGP

Expected results: UDN should be advertised with eBGP

Additional info:

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Affected Platforms:

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1. internal CI failure
2. customer issue / SD
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