Cisco CUCM – Intercluster Lookup Service

Hey people,

Today I’m going to explain the concept of a good feature, called ILS (Intercluster Lookup Service).
ILS enables different CUCM Cluster to exchange directory URI with other clusters in an ILS network, allowing you to create networks of remote CUCM clusters. So, when you configure ILS on multiple clusters, it updates CUCM with the current status of remote clusters in the ILS network.
An ILS network comprises the following components:

Hub Clusters
Hub clusters form the backbone of an ILS network. Hub clusters exchange ILS updates with the other hub clusters in the ILS network, and then relay that information to and from their spoke clusters.

Spoke Clusters
A spoke cluster connects to the hub cluster in an ILS network to relay ILS updates to and from the rest of the ILS network. Spoke clusters contact only their local hub cluster and never directly contact other hub clusters or other spoke clusters. A spoke cluster can have only one hub cluster.

Global Dial Plan Imported Catalogues
To provide URI dialling compatibility with third-party systems, you can manually import a third-party directory URI or +E.164 number catalog from a CSV file into any hub cluster in the ILS network

CONFIGURATION

Let’s go deep to the configuration. For that, I’m going to use this topology as example:
2 CUCM clusters in the ILS network.

  • 10.106.79.71 – HQ Cluster
  • 10.106.79.83 – BR Cluster

topology.png

  • Activate Intercluster Lookup Service on all the CUCM Publisher

    You must activate the Intercluster Lookup Service to configure Cluster IDs and Remote Clusters.
    From Cisco Unified Serviceability, choose Tools > Service Activation.
    From the Server drop-down list, choose the node and then click Go.
    Select ‘Intercluster Lookup Service’ and Save.

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  • Configure Cluster IDs

    You must configure a unique cluster ID for each cluster in the ILS network. The clusters use this unique cluster ID and peer ID when they exchange status messages.
    In Cisco Unified Communications Manager Administration, choose System > Enterprise Parameters.
    In the Enterprise Parameters Configuration window Cluster ID field, enter a name of the cluster that you
    want to configure in your network.

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  • Activate ILS on the Hub Cluster

    You must configure each cluster in your ILS network as either a hub cluster or a spoke cluster. Each ILS network must have at least one hub cluster. You can connect a hub cluster to other hub clusters, or you can configure a hub cluster as the only hub cluster in the network. In addition, you can connect a hub cluster to multiple spoke clusters, or you can configure the hub cluster with no spoke clusters.

    Now, considering the Node 10.102.79.71 as the ILS HUB Cluster.

    Go to Advanced Features > ILS Configuration > and configure as follows.

    AA1.png

    Route String: This will be a unique string that will be advertised to the other clusters. Other ILS peers use Route String to route the call.

    Above configuration uses ‘Password’ based ILS authentication and synchronize the clusters every 1 minute.
    The moment you click Save, it will ask for ILS Registrar Server. Since I do not have any other HUB cluster, we can leave blank and click OK.

    4.png

  • Activate ILS on the Spoke Cluster

    Now, the node 10.106.79.83 will be  the SPOKE cluster.
    Go to Advanced Features > ILS Configuration > and configure as follows.

    A2.png
    When you click Save, enter the Registrar server as the HUB cluster 10.106.79.71.

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    Now refresh the ILS configuration to see the updated status.

    A3.png

  • Configuring URIs for the End Users

    Go to User Management > End User > and select the user you want to enable URI.
    For LDAP user, make sure the URI is synced from LDAP server. For the local users, you can set a URI as shown below.
    CUCM End User URI Configuration.png

    Then, go to the Controlled Devices section and assign the user’s desk phone as the controlled device. Also, configure the primary extension (mandatory!!).

    Primary extension for URI dialing.png

    Now go to the Directory number configuration(e.g. 1002). Now you will be able to see the URI field.

    Direcory URI configuration CUCM.png

  • Verify the Learned Directory URIs

    Go to Call Routing > Global Dial Plan Replication > Learned Directory URIs

    9.pngA4.png

    Any of the URI learned via ILS will be having 2 unique values. One is the Route String and another one is Cluster ID. Route String is used to route the call back to the respective cluster via a separate SIP trunk.
    ILS will only take care of advertising the URIs between clusters. They do not participate in call routing. For dialling the URI from one cluster to another, we need to have a separate SIP trunk.

  • ILS Restrictions


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  • ILS Troubleshooting

    Here are some Troubleshooting Tips:

    Issue: Local Cluster Cannot Connect to the ILS Network

    To troubleshoot connection issues within the local cluster, open RTMT and run alarms and diagnostic traces on that publisher node. If you receive an error message when trying to establish ILS between your clusters, you can try to restart the Cisco Intercluster Lookup service from Cisco Unified Serviceability Administration. In addition, connection issues may arise if authentication is improperly configured between clusters. Check authentication in the following manner:
    • If you are using TLS, make sure that all clusters in the network are using TLSand that Tomcat certificates have been exchanged for all the servers that need to communicate.
    • If you are using TCP password authentication, make sure that all ILS clusters are using TCP password authentication and that the same TCP password is assigned across the network.

    Issue: Directory URIs Are Not Being Replicated Across the ILS Network

    This error can occur for a variety of reasons. Check the following:

    • Verify that all clusters in the network are configured to exchange global dial plan data. If a hub cluster is not configured to exchange global dial plan data, none of that hub’s spoke clusters will be able to exchange directory URI catalogs.
    • Allow enough time for end-to-end replication based on synchronization intervals (set on the ILS Configuration page) that are configured for all the clusters involved in the path. All clusters in an ILS network are a maximum of three hops from every other cluster in the network.
    • Use the utils ils showpeerinfo CLI command to monitor replication progress by looking at the USN values for the remote clusters.
    • Increase speed of replication by changing the ILS Sync Throttle Service Parameter. Note that a low setting can affect system performance.
    • Verify that all clusters in the ILS network have unique cluster IDs and that none of the clusters are configured with Stand Alone Cluster as its cluster ID. You can check Cluster IDs in Cisco Unified CM Administration under System > Enterprise Parameters.

    Issue: Global Dial Plan Replication Is Configured, but Unified CM Still Cannot Place a Call to A Learned Directory URI or Learned Number in a Remote ILS Cluster

    This condition can occur if ILS and Global Dial Plan Replication are enabled on all clusters in the network, but SIP route patterns that route to the route strings for the remote clusters have not been configured. Do the following:
    • In the ILS Clusters and Global Dial Plan Imported Catalogs view in the ILS Configuration window, check the route string for the remote cluster.
    • In the SIP Route Pattern configuration window, make sure that you have route patterns that map to the route strings for your remote clusters

    Hope you’ve enjoyed Smile

    See ya!

    Bruno