Google remotely monitors and maintains the Google Distributed Cloud connected
hardware. For this purpose, Google engineers have Secure Shell (SSH) access to
the Distributed Cloud connected hardware. If Google detects an issue,
a Google engineer contacts you to troubleshoot and resolve it. If you have
identified an issue yourself, contact Google Support immediately to diagnose
and resolve it.

## Corrupt BGP sessions in Cloud Router resources used by VPN connections

Distributed Cloud VPN connections rely on BGP sessions
established and managed by their corresponding Cloud Router resources to
advertise routes between the Distributed Cloud connected
cluster and Google Cloud. If you modify the configuration of a
Cloud Router resource associated with a Distributed Cloud
VPN connection, that connection can stop functioning.

To recover the corrupt BGP session configuration in the affected Cloud Router,
complete the following steps:

1. In the Google Cloud console, get the name of the corrupt BGP session. For example:

       INTERFACE=anthos-mcc-34987234

2. Get the peer BGP and the Cloud Router BGP IP addresses
   for the corrupted BGP session, as well as the peer ASN used by the affected Distributed Cloud VPN connection. For example:

       GDCE_BGP_IP=168.254.208.74
       CLOUD_ROUTER_BGP_IP=168.254.208.73
       PEER_ASN=65506

   If you deleted the BGP session, get this information from the Distributed Cloud connected cluster instead:
   1. Get the cluster credentials:

      ```
      gcloud edge-cloud container clusters get-credentials CLUSTER_ID \
        --location REGION \
        --project PROJECT_ID
      ```

      Replace the following:
      - `CLUSTER_ID`: the name of the target cluster.
      - `REGION`: the Google Cloud region in which the target cluster is created.
      - `PROJECT_ID`: the ID of the target Google Cloud project.
   2. Get the configuration of the `MultiClusterConnectivityConfig` resource:

      ```
      kubectl get multiclusterconnectivityconfig -A
      ```

      The command returns output similar to the following:

           NAMESPACE     NAME                   LOCAL ASN              PEER ASN
           kube-system   MultiClusterConfig1    65505                   65506
           ```

   3. Get the peer BGP IP address, the Cloud Router IP address, and the
      BGP session ASN:

      ```
      kubectl describe multiclusterconnectivityconfig -n kube-system MCC_CONFIG_NAME   
      ```

      Replace `MCC_CONFIG_NAME` with the name of the
      `MultiClusterConfigResource` that you obtained in the previous step.

      The command returns output similar to the following:

           ​​Spec:
           Asns:
             Peer:  65505
             Self:  65506 # GDCE ASN
           Tunnels:
             Ike Key:
               Name:       MCC_CONFIG_NAME-0
               Namespace:  kube-system
             Peer:
               Bgp IP:      169.254.208.73 # Cloud Router BGP IP
               Private IP:  34.157.98.148
               Public IP:   34.157.98.148
             Self:
               Bgp IP:      169.254.208.74 # GDCE BGP IP
               Private IP:  10.100.29.49
               Public IP:   208.117.254.68
           ```

3. In the Google Cloud console, get the name, region, and
   Google Cloud project name for the corrupted VPN tunnel. For example:

       VPN_TUNNEL=VPNTunnel1
       REGION=US-East1
       VPC_PROJECT_ID=VPC-Project-1

4. Delete the corrupted BGP session from the Cloud Router configuration.

5. Create a new Cloud Router interface:

   ```
   gcloud compute routers add-interface --interface-name=INTERFACE_NAME \
      --vpn-tunnel=TUNNEL_NAME \ 
      --ip-address=ROUTER_BGP_IP \
      --project=VPC_PROJECT_ID \
      --region=REGION \      
      --mask-length=30
   ```

   Replace the following:
   - `INTERFACE_NAME`: a descriptive name that uniquely identifies this interface.
   - `TUNNEL_NAME`: the name of the VPN tunnel that you obtained in the previous step.
   - `ROUTER_BGP_IP`: the BGP IP address of the Cloud Router that you obtained earlier in this procedure.
   - `VPC_PROJECT_ID`: the ID of the target VPC Google Cloud project.
   - `REGION`: the Google Cloud region in which the target VPC Google Cloud project has been created.
6. Create the BGP peer:

   ```
   gcloud compute routers add-bgp-peer --interface=INTERFACE_NAME \
      --peer-name=TUNNEL_NAME \
      --region REGION \
      --project=VPC_PROJECT_ID \
      --peer-ip-address=GDCE_BGP_IP \
      --peer-asn=GDCE_BGP_ASN \
      --advertised-route-priority=100 \
      --advertisement-mode=DEFAULT
   ```

   Replace the following:
   - `INTERFACE_NAME`: the name of the interface that you created in the previous step.
   - `TUNNEL_NAME`: the name of the VPN tunnel that you used to create the interface in the previous step.
   - `REGION`: the Google Cloud region in which the target VPC Google Cloud project is created.
   - `VPC_PROJECT_ID`: the ID of the target VPC Google Cloud project.
   - `GDCE_BGP_IP`: the Distributed Cloud peer BGP IP address that you obtained earlier in this procedure.
   - `GDCE_BGP_ASN`: the Distributed Cloud peer BGP ASN that you obtained earlier in this procedure.

At this point, the BGP session is back up and operational.