Webex Calling Options

In this sample chapter from CCNP and CCIE Collaboration Core CLCOR 350-801 Official Cert Guide, 2nd Edition, you will learn PSTN options for Webex Calling, routers supporting local gateway, and deployment scenarios for the local gateway. This chapter covers the following objective from the Cisco Collaboration Core Technologies v1.1 (CLCOR 350-801) exam: 3.4 Describe cloud calling hybrid local gateway.

This chapter covers the following topics:

• PSTN Options for Webex Calling: This topic will identify the PSTN options available for the Webex Calling solution.

• Routers Supporting Local Gateway: This topic will review the different routers that can be used to support the Local Gateway functions for Webex Calling.

• Deployment Scenarios for the Local Gateway: This topic will overview the various deployment scenarios for how a Local Gateway can be deployed both with and without a Cisco Unified Communications Manager.

Up to this point, we have established that Webex is a cloud-based solution designed to support any company, regardless of size. Webex Calling revolves around the ability to call out across the public switched telephone network (PSTN) from IP-based devices registered to Webex Control Hub. The size of the company and the options you choose with your Webex subscription will affect the complexity level required to deploy Webex Calling. For small and medium businesses (SMBs) there is a very affordable and simple Webex Calling option. Larger enterprises will need to deploy the more complex solution using the Local Gateway. Before Webex Calling is deployed, you should understand each of the topics discussed in this chapter:

• PSTN options for Webex Calling

  • Cloud-connected PSTN (CCP)

  • Cisco PSTN

  • Premises-based PSTN

• Routers supporting local gateway

  • Cisco routers

  • Third-party routers

  • Registration- and certificate-based local gateway

  • Deployment scenarios for the local gateway

This chapter covers the following objectives from the Cisco Collaboration Core Technologies v1.1 (CLCOR 350-801) exam:

• 3.4 Describe cloud calling hybrid local gateway

“Do I Know This Already?” Quiz

The “Do I Know This Already?” quiz allows you to assess whether you should read this entire chapter thoroughly or jump to the “Exam Preparation Tasks” section. If you are in doubt about your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 24-1 lists the major headings in this chapter and their corresponding “Do I Know This Already?” quiz questions. You can find the answers in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes.”

Table 24-1 “Do I Know This Already?” Section-to-Question Mapping

1. An administrator is setting up Webex Calling for their organization. They currently use the Cisco Unified Communications Manager for on-premises call control. They plan to use Webex also for hybrid communication. Which of the following PSTN options should the administrator choose?

1. Hybrid-based PSTN

2. Cisco PSTN

3. Cloud Connected PSTN

4. Premises-based PSTN

2. Which of the following statements is true regarding Webex Calling using Cisco PSTN?

1. Toll-free numbers are supported with the Cisco Calling Plan.

2. Existing Webex Calling locations can transition to the Cisco Calling Plan.

3. The Cisco Calling Plan does support Webex Contact Center.

4. The Cisco Calling Plan allows you to order up to 100 new phone numbers at a time.

3. Which of the following components must be configured in Webex Control Hub before Webex Calling will work using Premises-based PSTN?

1. Virtual Lines

2. Service Settings

3. Locations

4. PSTN

4. Which of the following SBC products can function as a Local Gateway with Webex Calling? (Select all that apply.)

1. Catalyst 8000v

2. AP 1100v

3. Mediant 8000B/C Gateway & E-SBC

4. ISR880

5. AP 1100

6. Mediant 4000/B SBC

5. Which of the following Cisco routers can be deployed on Amazon AWS to support 3000 concurrent calls?

1. C1000v – 1vcpu (4GB)

2. C1000v – 4vcpu (8GB)

3. C8000v-M (4GB)

4. C8000v-L (8GB)

5. The correct answer is C8000v-M (4GB).

6. Which of the following devices are considered Edge Platforms? (Select all that apply.)

1. ISR1100

2. C8200

3. ISR 4461

4. CSR1000v

5. C8300

6. C8000v

7. Which of the following connection types for Webex Calling allows the greatest number of concurrent calls?

1. SCCP-based

2. Certificate-based

3. MMP-based

4. Registration-based

5. SIP-based

8. When considering which Local Gateway deployment option to implement, which of the following items should you consider? (Select all that apply.)

1. Ownership of PSTN gateway

2. Desired call throughput of the site PSTN connection

3. TDM vs. IP gateway connections

4. Age of gateways

5. Cisco router type

9. Which of the following is a recommended deployment option for the Local Gateway when deploying Webex Calling using the Premises-based PSTN method?

1. Local Gateway and PSTN Connection Co-located

2. Dedicated Local Gateway and PSTN Connections

3. Cisco Unified Communications Manager with Co-located PSTN Gateway/SBC and Local Gateway

4. Partner Hosted Local Gateways

10. Which of the following is the correct call flow in a Webex Calling deployment using Premises-based PSTN?

1. PSTN Gateway > Local Gateway > Cisco Unified Communications Manager > Webex

2. PSTN Gateway > Webex > Local Gateway > Cisco Unified Communications Manager

3. Cisco Unified Communications Manager > PSTN Gateway > Webex > Local Gateway

4. PSTN Gateway > Cisco Unified Communications Manager > Local Gateway > Webex

PSTN Options for Webex Calling

Webex Calling Plans, Trunks, and Route Groups provide you with the ability to configure Webex Calling to manage calls between Webex Calling–hosted users and on-premises IP public branch exchange (PBX) users. This solution lets you configure hosted users to use Cloud PSTN (Cloud Connected PSTN [CCP] or Cisco PSTN) or Premises-based PSTN. Once your location is enabled, you must set up PSTN connectivity for Webex Calling users within that location. The following PSTN options are available:

• Cisco PSTN: Choose this option if you’d like a bundled solution that allows you to order new PSTN numbers and port existing numbers to Cisco. The Cisco PSTN option is only available under the following conditions:

  • You have purchased and enabled the Cisco Calling Plan.

  • The location is in a country where Cisco Calling Plan is supported.

• Cloud Connected PSTN: Choose this option if you’re looking for a cloud solution that doesn’t require deployment of local hardware and then select your CCP provider of choice. Cloud PSTN (Cisco PSTN or CCP) can only be used to provide PSTN access for Webex Calling users. Calls originating from on-premises users can’t access cloud PSTN.

• Premises-based PSTN (Local Gateway): Choose this option if you want to keep your current PSTN provider. Trunks for Premises-based PSTN through Local Gateway can also be used to connect to on-premises PBXs. You can retain existing Local Gateway functionality without making any configuration changes. Locations using Local Gateway are set to Premises-based PSTN and Local Gateways become Trunks.

Configure your selected PSTN connection within Control Hub by selecting Management > Locations and clicking the Calling tab. In the Calling Connection section, click Manage and then select your PSTN connection of choice.

Cloud Connected PSTN (CCP)

CCP enables global cloud PSTN calling options for Webex Calling Dedicated Instance (DI). Dedicated Instance leverages existing CCP partner peering with Webex Calling for this feature. To enable this feature for DI, Webex Calling introduces a new call routing construct called Route Lists. Route Lists in Webex Calling are lists of numbers reachable through a Route Group. Each Route List is exclusively assigned to a Location that supplies up to 40,000 unassigned numbers from the hosted pool. Only customers with DI entitlements can see or configure Route Lists in Control Hub. Figure 24-1 illustrates a Webex Calling organization with two Route Lists in their respective locations, each of them pointing to the same Route Group/Trunk, which in turn routes to a single Dedicated Instance cluster.

For E911 locations, all emergency calls should use the built-in Dedicated Instance E911 capability. E911 calls should not be sent to the Webex Calling Organization.

For non-E911 Dedicated Instance locations that use Cloud Connected PSTN, emergency calls can be sent to the Webex Calling Organization. The calling number of the emergency call must match a PSTN number in a Route List. The Route List will identify the Webex Calling location that the emergency call belongs to and overwrite the calling number with the Emergency Callback Number (ECBN) for that Webex Calling location.

If the calling device on Dedicated Instance does not have valid Direct Inward Dialing (DID), then it should be configured to send the correct ECBN as the calling number for all emergency calls. This will then match the correct Route List in the Webex Calling Organization and send the call appropriately.

Use the following steps to enable CCP for DI:

• Step 1. Provision Location(s) in Control Hub.

  1. Select Cloud Connected PSTN as the connection type for the location and select the corresponding CCP provider.

  2. Order PSTN numbers from a CCP provider (integrated or non-integrated). Integrated providers will supply numbers directly to Control Hub, where they will appear automatically. For non-integrated providers, import the PSTN numbers as follows:

     1. Sign in to Control Hub and go to the Calling > Numbers menu. Click the Manage drop-down menu on the right side of the table and select Add.

     2. Select Location from the drop-down menu on the Selection page. The PSTN connection associated with the location is listed against the location.

     3. Add the PSTN numbers purchased in the fields on the Select Numbers page. You may add up to 1000 numbers and choose to activate them immediately or later. Click Save after all numbers have been added. The confirmation page displays the PSTN numbers that have been added to the location.

  3. Perform the following steps for each Location to create a Route List, assign it to an appropriate Route Group, and select which numbers will be assigned to DI:

     1. Navigate to Calling > Route Lists and choose an option from the list to view its properties.

     2. Select a Route Group from the Routing Choice menu.

     3. Click Add Numbers and enter the numbers associated with the Route List.

     4. Select the PSTN numbers in the Route List that are designated for Dedicated Instance (in/out) and then click Add. As part of Dedicated Instance service activation, SIP Trunks to Dedicated Instance and the Route Groups are created in Control Hub (the name starts with “WxC-DI”).

  4. Configure Dial Plans in Webex Calling with patterns pointing to Dedicated Instance and associate them with a Route Group.

• Step 2. Configure Dedicated Instance:

  1. Configure the PSTN DIDs and assign them to phones, users, hunt pilot, and so on.

  2. Configure the dial plan on Dedicated Instance to route PSTN calls to Webex Calling, using the Route Group, Route List, and SIP Trunks configured during Dedicated Instance service activation.

  3. To enable international calling, select the relevant location in the Control Hub Calling page. Navigate to Advanced > Outgoing and Incoming Permissions > Outgoing Calls > International and select Allow from the drop-down menu.

Cisco PSTN

The Cisco Calling Plan offers a bundled solution to simplify your cloud calling experience. As a Webex Calling customer, you can order new PSTN numbers or port existing numbers to Cisco easily and with the full support of Cisco and its partners.

You can select varied connections for multi-site applications. For example, you can select Cisco PSTN for one location, Cloud-Connected PSTN (CCP) for a second location, and Premises-based PSTN for the third location. When choosing the Cisco Calling Plan, the following applies:

• Requirements:

  • Your partner must be an authorized Webex Calling partner and have accepted the new Webex Calling addendum through enrollment into the Webex Calling PSTN program.

  • Your partner places an order with Cisco Calling Plan licenses (Outbound Calling Plan and Telephone Numbers) within the Cisco Commerce Workspace (CCW).

• Limitations:

  • Cisco Calling Plan service is currently available to specified countries and regions. As this list is constantly changing, you will need to inquire what countries are participating at the time you sign up.

  • Existing Webex Calling locations can’t transition to the Cisco Calling Plan.

  • Toll-free numbers aren’t currently available. You can’t order new toll-free numbers or port existing toll-free numbers to the Cisco Calling Plan.

  • You can order a maximum of 100 new phone numbers at a time. Additional numbers can be placed as a separate order.

  • Cisco Calling Plan is available with the free Webex Calling trial offer. When using the Cisco Calling Plan with a Webex Calling trial, you can create a maximum of 10 new phone numbers.

  • Number porting isn’t available with a Webex Calling trial.

  • Cisco Calling Plan isn’t supported with Webex Contact Center or other use in which high-concurrent calls or high-volume calls are frequently made.

Use the following steps to enable Webex Calling using Cisco PSTN.

• Step 1. From the customer view in https://admin.webex.com, go to Management > Locations and select the location you want to update.

• Step 2. Select the Calling tab and click Manage next to PSTN Connection.

• Step 3. Select Cisco PSTN and click Next.

• Step 4. Enter the contact information and click Next. This field is for the contact information of the person who will sign the legal contract with Cisco.

• Step 5. Enter the Emergency Services Address (ESA) and click Save. By default, the ESA entered here is applied to all phone numbers for this location. You can change the ESA for an individual user if needed. For example, you may need to change the ESA if you have a remote employee who works from home.

• Step 6. On the summary screen, do one of the following:

  • Click Add numbers.

  • Click Done.

You can add numbers to your calling plan later.

Premises-Based PSTN

Premises-based PSTN allows organizations to bring their own carrier by interconnecting any service provider’s PSTN with a Premises-based Local Gateway that tightly integrates to Cisco's Webex Calling cloud. This service is provided through existing enterprise routing infrastructure that uses a trunk for the Local Gateway either without an on-premises IP PBX or with an existing Cisco Unified Communications Manager call environment. The PSTN connection can be accessed using Cisco Unified Border Element (UBE) or through an IOS gateway with Primary Rate Interface (PRI) cards. Cisco UBE is the recommended deployment option for Premises-based PSTN and will be the sole focus throughout the rest of Part VI, “Webex Calling.”

The Webex Control Hub was discussed extensively in Chapter 23, “Adding Users and Devices in Webex Control Hub.” As a review, the Webex Control Hub is a management portal that integrates with Webex Calling to streamline your orders and configuration as well as to centralize your management of the bundled offer: Webex Calling, Webex Messaging, and Webex Meeting. Webex Control Hub is the central point for provisioning all services, devices, and users. You can do first-time setup of your calling service, register MPP phones to the cloud, and configure users by associating devices and adding numbers, services, calling features, and so on. Also, from Control Hub, you can cross-launch to the Calling Admin Portal, which is used to initially configure Webex Calling and to manage it once everything is set up. Important components that need to be configured to enable Webex Calling include Numbers, Locations, Call Routing, and Managed Gateways. These components will be discussed further in Chapter 26, “Webex Calling Using a Local Gateway.” Other configuration options include Virtual Lines, Features, PSTN (used for managing cloud PSTN orders), Service Settings, and Client Settings.

The Local Gateway is an enterprise or partner-managed edge device for PSTN interworking and legacy PBX interworking, including Cisco Unified Communications Manager. You can use Webex Control Hub to assign a local gateway to a location, after which Control Hub provides parameters that you can configure on a router. These steps register the Local Gateway with the cloud, and then PSTN service is provided through the gateway to Webex Calling users in a specific location. All communication to and from the cloud is secured using TLS transport for SIP and SRTP for media.

Cisco UBE can be used to connect an enterprise to a telephony service provider over SIP, who will interconnect calls out to the PSTN, and vice versa. If an existing Cisco UBE enterprise deployment is being modified to also utilize the local gateway function for Cisco Webex Calling, Cisco UBE High Availability (HA) can be deployed to ensure call flows and functionalities are not interrupted. Cisco UBE HA Layer 2 box-to-box redundancy uses the Redundancy Group (RG) infrastructure protocol to form an active/standby pair of routers. This pair shares the same virtual IP address (VIP) across their respective interfaces and continually exchange status messages. Cisco UBE session information is check-pointed across the pair of routers, enabling the standby router to take all Cisco UBE call processing responsibilities over immediately if the active router goes out of service, resulting in stateful preservation of signaling and media. As of IOS-XE 16.12.2, Cisco UBE HA can be deployed as a Local Gateway for Cisco Webex Calling Trunk Premises-based PSTN deployments. The purpose of this chapter is to provide an introduction to Webex Calling options, so we will not be diving any deeper into Cisco UBE HA in this book.

Routers Supporting Local Gateway

Webex Local Gateway can be hosted on a variety of Cisco IOS-XE routers and a select group of third-party routers. This topic will cover the platforms, capacities, and software versions required to support Local Gateway functionality on Cisco routes and third-party routers. This chapter will also cover the differences between the registration-based Local Gateway and certificate-based Local Gateway settings.

Cisco Routers

The 1100 and 4000 series of IOS-XE devices are the entry point for Local Gateways and the oldest devices supported to function as Local Gateways. These are the same devices that function today as branch gateways in an on-premises-based VoIP system. This allows the rapid conversion from on-premises to cloud-based or a hybrid calling model without requiring router upgrades.

The smallest supported router for Local Gateway is the ISR 1100 series. These small devices are capable of handling 500 calls with up to five calls per second (CPS). The routers are available with different amounts of memory, WAN, and Ethernet interfaces to suit the needs of small sites. Since telephone ports are not supported with the ISR 1100 series, these routers could only be used as a Cisco UBE using SIP trunks. The ISR 1100 series products went end of sale (EOS) on May 9, 2023 and have an end of support date of May 31, 2028.

The 4000 series of Integrated Services Routers are able to handle the demands of most branch office needs. A wide range of interface choice for WAN, Ethernet, and Telephony allow the user to customize the router to suit their needs. The router can be used as a Cisco UBE for full SIP-based communications but also as a Time Division Multiplexing (TDM) gateway using older circuits such as T1/E1 PRI. The product line supports 500 calls with four CPS on the smallest ISR 4321, up to 10,000 calls and 55 CPS on the largest ISR 4461. This product line eases the process of finding a router with the right mix of interfaces and performance needed for the branch site in your organization. The ISR 4300/4400 line is set to go end of sale (EOS) on November 7, 2023. The product will be supported for several more years, but the latest IOS XE release will be either 17.9 or 17.12, depending on the software train you are utilizing. Table 24-2 identifies all the 1100 and 4000 series routers that support Local Gateway.

Table 24-2 Local Gateway Support on 1100 and 4000 Series Routers

The replacements for the ISR 1000 and 4000 routers are the Catalyst 8000 Edge Platforms. The Cisco Catalyst 8300 Series Edge Platforms are best-of-breed, 5G-ready, cloud edge platforms designed for accelerated services, multi-layer security, cloud-native agility, and edge intelligence to accelerate your journey to cloud. The C8000 line is broken into two series similar to the 4000 series lineup. The smaller 8200 series provides multi-core processors, up to 32GB of DRAM, up to four Ethernet ports (two support SFP), and one Network Interface Module, which can support various WAN and Telephony interfaces.

The C8300 products contain multicore processors, expandable memory, and up to six Ethernet ports. Two of those ports can support Small Form Factor Pluggable adapters to allow copper or fiber connections. The Edge Platforms also come with dual power supplies for greater redundancy. Numerous WAN and Telephony interface cards allow you to tailor the product to the site’s voice and data services, which require support at a branch site.

When the C8000 line is used as a Local Gateway, its performance is upgraded from the ISR 4000 series it replaces. Call throughput ranges from 1500 (middle of the pack for ISR 4000) on the small end to 10,000 on the higher end. Sustainable CPS rates of nine on the C8200L to 55 on the C8300-2N2S-4T2X meet the needs of most branch locations. Table 24-3 identifies all the 1100 and 4000 series routers that support Local Gateway.

Table 24-3 Local Gateway Support on Catalyst 8000 Edge Routers

A third option for Local Gateways is either the CSR1000v or the C8000v. Both products are virtual machines that can run in a variety of virtual environments. The Cloud Services Router 1000v is a virtual IOS-XE router that can run in VMware ESXi, Citrix XenServer, Microsoft Hyper-V, SuSE KVM, or Red Hat KVM virtual environments. The CSR1000v can also be deployed in Microsoft Azure, Amazon EC2, and Google Cloud Platform. The CSR1000v can support up to IOS-XE version 17.3 software. After that version, the branding and licensing was changed to reflect the new product name of Catalyst 8000v.

The Catalyst 8000v is a continuation of the CSR1000v. The C8000v is a software-based virtual router that combines the functionalities of Cisco Cloud Services Router (Cisco CSR1000V) and Cisco Integrated Services Virtual Router (Cisco ISRv) into a single image that is intended for deployment in cloud and virtual data centers. It is supported in ESXi, KVM, NFVIS hypervisors. Further, you can deploy this router on public cloud providers such as Amazon Web Services (AWS), Microsoft Azure, Google Cloud Platform (GCP), and Alibaba Cloud.

The router can be deployed as a virtual machine in your virtual environment, and it can be created as a small, medium, or large virtual machine using increasing amounts of vCPU, memory, and other resources. The number of concurrent and sustained CPS also increases. If the C8000v is deployed in a cloud environment such as Microsoft Azure or Amazon AWS, the medium VM is deployed with 3000 concurrent calls and 20 CPS. Table 24-4 identifies the 1000v and 8000v virtual routers that support Local Gateway.

Table 24-4 Local Gateway Support on 1000v and 8000v Virtual Routers

Third-Party Routers

A relatively new addition to the supported Session Border Controller area are third-party Session Border Controllers (SBCs). The following products running Oracle SBC version 9.0 software are supported as a Local Gateway with Webex Calling:

• AP 1100

• AP3900

• AP 4600

• AP 6300

• AP 6350

• AP 3950 (Starting from SBC 9.0)

• AP 4900 (Starting from SBC 9.0)

• VME

• Oracle SBC on Public Cloud

The following AudioCodes SBCs running software version 7.40A.250.440 or later are supported as Local Gateway with Webex Calling:

• Mediant 500 Gateway and E-SBC

• Mediant 800B/C Gateway and E-SBC

• Mediant 1000B Gateway and E-SBC

• Mediant 2600 E-SBC

• Mediant 4000/B SBC

• Mediant 9000, 9030, 9080 SBC

• Mediant Software SBC (VE/SE/CE)

Finally, the Ribbon line of SBCs has also received approval to function as Local Gateways with Webex Calling. The following Ribbon SBCs running Ribbon Code version 10.1.0 or higher are supported as Local Gateways:

• SBC 5000

• SBC 7000

• SBC SWe

Registration- and Certificate-Based Local Gateway

While it is true that an ISR 4461 can handle 10,000 concurrent calls, that capacity can be restricted to as low as 250 if the connection to the Webex cloud is not chosen correctly. To understand this issue, it is important to understand that there are two ways to connect to the Webex Calling system:

• Registration-based Local Gateway

• Certificate-based Local Gateway

In the registration-based Local Gateway connection, you create the connection in Control Hub and you are provided with the elements needed to allow your Local Gateway to create a TCP connection to the cloud. This is a one-way connection from the Local Gateway to the cloud. One of the big benefits of this connection type is that a technician with limited IOS skills can successfully deploy a Local Gateway behind a NAT/firewall without requiring changes to the NAT or firewall. The connection does not require CA signed certificates, which reduces complexity and cost. However, since the registration consists of a single TCP connection, the link has a lower capacity and is not as durable if there are network issues such as high latency and packet loss. This means that no matter what SBC platform you are using, you are limited to 250 concurrent calls per trunk built on that device. It is possible to build multiple trunks on a single Local Gateway. Careful configuration of outbound interfaces, SIP listening ports, dial-peers, and load balancing for the on-premises Cisco Unified Communications Manager can allow you to exceed the 250-call limit. Figure 24-2 illustrates the connection flow for Webex Calling using registration-based Local Gateway.

The certificate-based method of connecting a Local Gateway fixes the capacity issue by using Mutual TLS as the connection type. This method also uses four bi-directional connections rather than a single one-way connection, as with the registration-based connection. This connection type requires CA signed certificates in the Local Gateway. The engineer also needs to add the Webex Calling trust bundle into the Local Gateway so that the SBC trusts the certificates of Webex Calling.

A connection is configured to endure four fully qualified domain names (FQDNs) or a DNS Service Record (SRV) that points to the Access SBCs of Webex Calling. If configured correctly, four bi-directional TLS connections will be created to carry traffic to and from the Local Gateway and Webex Calling. NAT/firewall traversal is possible with the certificate-based connection method using Session Traversal Using NAT (STUN). Figure 24-3 illustrates the connection flow for Webex Calling using certificate-based Local Gateway.

As you can see from these two descriptions, if you are looking for an easy installation and only have a capacity need below 250 concurrent calls over the public Internet, it is recommended that you use the registration-based connection method. If you require up to 2000 concurrent calls over the public Internet, the solution will be certificate-based. It is possible to reach up to 6500 concurrent calls with the certificate-based connection method, but this will require a dedicated Interconnect connection to Webex Edge Connect. If you wish to use any of the newly supported third-party SBCs, you will need to use the certificate-based connection method as well. Table 24-5 identifies sizing parameters for a Local Gateway based on registration type.

Table 24-5 Local Gateway Sizing Parameters Based on Registration Type

Deployment Scenarios for the Local Gateway

Webex Local Gateways can be deployed in different configurations to adapt to the needs of individual customers, depending on several factors. Does the Local Gateway and the PSTN connection share the same physical or virtual hardware? Does the site contain an IP PBX such as Cisco Unified Communications Manager? Is the Local Gateway hosted offsite from the customer through a service provider (SP) or value-added reseller (VAR)? Each of these factors will be address in the following scenarios. The two biggest factors you should you consider when deploying a Local Gateway are who owns the PSTN gateway and what is your desired throughput of the site PSTN connection?

The first scenario to consider is a company that uses all Webex endpoints but wishes to use its local PSTN’s circuits. If the customer doesn’t already have a device to handle the connection to the PSTN, a single router supporting Local Gateway and PSTN services is a good solution. The router or edge device will supply the Local Gateway functionality as well as the connection to the PSTN. In this scenario, the Webex dial plan routes all non-Webex calls to the trunk pointing to the Local Gateway. The Local Gateway configuration provides the secure connection to the Webex cloud and contains dial-peers, which route calls to the PSTN. Figure 24-4 illustrates a single site deployment for Webex Calling where the PSTN connection and Local Gateway are co-located.

The second scenario separates the Local Gateway function from the PSTN gateway using separate routers. The most common reason for this deployment type is to increase capacity. The Local Gateway handles all calls to and from the Webex cloud. Any call not destined for Webex is passed to the PSTN gateway. The PSTN gateway uses similar logic to send any calls not designated for the PSTN to the Local Gateway. This simplifies the configuration of each device and allows higher call capacity through each router. Figure 24-5 illustrates a single site deployment for Webex Calling where the PSTN connection and Local Gateway use dedicated routers for each service. This is the recommended deployment option for Webex Calling when an IP PBX is not being used.

Another reason to use this deployment model would be if the customer does not control the PSTN device. The customer configures the Local Gateway to hand off all incoming calls from Webex to the PSTN device. Similarly, the PSTN device sends all incoming calls to the Local Gateway.

Adding Cisco Unified Communications Manager to the customer site creates a new scenario because it changes the configuration a bit. In this case, the customer will want the calls from Webex to go to Cisco Unified Communications Manager since there will be an existing dial plan for both on-premises endpoints and the PSTN. Similar to the example of a location with a single router providing both Local Gateway and PSTN functions, the same type of router configuration can be used in this environment. The largest drawback would be the router’s capacity to handle sufficient traffic for Cisco Unified Communications Manager, Webex, and PSTN.

When calls are made from a Webex endpoint, any call not matching the Webex dial plan would be routed to the Local Gateway. The Local Gateway would pass the call to the Cisco Unified Communications Manager. The Cisco Unified Communications Manager dial plan would be leveraged to send calls to either a Cisco Unified Communications Manager–controlled endpoints or routed back the Local Gateway/PSTN device to hand the calls off to the PSTN.

Inbound calls to Webex from the PSTN would route to the PSTN gateway function of the router and onward to the Cisco Unified Communications Manager. The dial plan of the Cisco Unified Communications Manager will be used to determine if the call should be routed to a locally registered device or to a Webex-registered device. When the call is destined for a Webex-registered device, the Cisco Unified Communications Manager will route the call to the Local Gateway function of the router, which forwards the call to the Webex cloud, which will in turn route to the endpoint or phone. Figure 24-6 illustrates a single-site deployment for Webex Calling where the PSTN connection and Local Gateway are co-located on the same router and Cisco Unified Communications Manager is used for on-premises call control.

As you might have guessed, the forth scenario deals with using Cisco Unified Communications Manager and a dedicated router for the PSTN gateway function and Local Gateway function. This is the recommended option for Webex Calling using Cisco Unified Communications Manager. You will benefit from increased call capacity and more granule call control. This scenario is best suited for customers that have an existing on-premises call control solution that utilizes high call volume. The call flow for this scenario remains the same as the previously discussed scenario using a Cisco Unified Communications Manager, as shown next. Figure 24-7 illustrates a single-site deployment for Webex Calling where dedicated routers are used for the PSTN connection and Local Gateway, and Cisco Unified Communications Manager is used for on-premises call control.

• Webex > Local Gateway > Cisco Unified Communications Manager > PSTN Gateway

• PSTN Gateway > Cisco Unified Communications Manager > Local Gateway > Webex

Any of the scenarios outlined previously are acceptable deployments. However, when planning for future expansion or growth, it is recommended that you separate the Local Gateway and PSTN gateway functions to gain the highest capacity. In addition, the ownership of the devices (customer vs. PSTN provider) might play a role in the decision.

This brings us to the next scenario. Only one Local Gateway needs to be configured for each organization, but multiple Local Gateways can be configured as well by creating multiple locations in the Webex Control Hub. There are a couple rules that should be followed when creating multiple locations:

• You cannot assign multiple Local Gateways to a single location. Only one Local Gateway can be assigned per locations.

• You can assign a single Local Gateway to multiple locations.

Picture an organization that has three locations configured: Washington, DC, New York, NY, and London, UK. Washington and London have a Local Gateway assigned to them. New York simply uses the same Local Gateway as Washington. If a device registered to New York needs to place a call out the PSTN, the call will traverse from the New York location to Webex, back to Washington, then out the Local Gateway to the PSTN. This is how two or more locations can use the same Local Gateway. However, New York cannot use both the Washington and London local gateways because of the second rule outlined previously. Figure 24-8 illustrates how multiple Local Gateways can be used over multiple locations.

There is one final scenario you need to understand. Endpoints registered to the Webex Control Hub will communicate directly with Webex in the cloud. They do not have to route calls through the Local Gateway first. That connection is over the Internet, just as you would connect to a website like Cisco.com. In this manner, these endpoints do not have to be co-located with the Local Gateway. Therefore, partners can provide Local Gateway services hosted within their own data centers on behalf of their customers. This could be an official SP or a VAR. In fact, many Cisco VAR partners offer this type of service today. Figure 24-9 illustrates how customers can use the on-premises PSTN Webex Calling option through a hosted Local Gateway within a Cisco Partner environment.

Exam Preparation Tasks

As mentioned in the section “How to Use This Book” in the Introduction, you have a couple of choices for exam preparation: the exercises here, Chapter 35, “Final Preparation,” and the exam simulation questions in the Pearson Test Prep Software Online.

Review All Key Topics

Review the most important topics in this chapter, noted with the Key Topics icon in the outer margin of the page. Table 24-6 lists a reference of these key topics and the page numbers on which each is found.

Table 24-6 Key Topics for Chapter 24

Define Key Terms

Define the following key terms from this chapter and check your answers in the glossary:

CCP

Cisco PSTN

Premises-based PSTN

Webex Calling DI

Webex Calling Route Lists

Local Gateway

Cisco UBE HA

Branch Gateways

Catalyst 8000 Edge Platforms

CSR1000v

C8000v

Registration-based Local Gateway

Certificate-based Local Gateway

Q & A

The answers to these questions appear in Appendix A. For more practice with exam format questions, use the Pearson Test Prep Software Online.

1. List the three PSTN options for Webex Calling.

2. List the five series of Cisco routers that support the Local Gateway.

3. What are the four companies that offer third-party routers to support the Local Gateway?

4. What are the two rules you must follow when creating multiple locations in the Webex Control Hub for Webex Calling?