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- In Use Case 1—Wireless-to-Wired Bonjour Gateway Service Policy—BYOD Employee AirPrint Example, Converged Access Bonjour Gateway Configuration
- In Use Case 2—Wireless-to-Wireless Bonjour Gateway Service Policy—BYOD Guest AirPlay Example, Converged Access Bonjour Gateway Configuration
- Use Case 3—Converged Access Multi-Node Bonjour Gateway Configuration Example
Bonjour is Apple’s zero-configuration protocol for advertising, discovering, and connecting to network services like file sharing, print sharing, media sharing, etc. The Bonjour protocol was originally designed for home network use and utilizes Multicast Domain Name Services (mDNS) via link-local multicasting to share network services. While this approach works well in home networks, a limitation of link-local multicasting is that these network services will only be shared within a single Layer 2 domain (such as a VLAN or WLAN). In a BYOD enterprise scenario, different WLANs and VLANs are used for different classes of devices, including corporate devices, employee devices, personal devices, and guest devices (as well as quarantine WLANs for unapproved devices). As such, basic Bonjour operations—such as printing to a wired printer from a wireless LAN—may not be natively supported.
To address this limitation and to facilitate the user demand of BYOD for Apple devices within the enterprise, Cisco has developed the Bonjour Gateway feature for its Wireless LAN Controllers (WLCs) and Catalyst switches. This feature solves the Layer 2 domain limitation for Bonjour by allowing the WLC or Catalyst switches to snoop, cache, and proxy-respond to Bonjour service requests that may reside on different Layer 2 domains. Additionally, these responses may be selectively controlled by administrative policies, so that only certain Bonjour services will be permitted in specific Layer 2 domains.
This document provides an overview of the Bonjour protocol and shows how the Bonjour Gateway feature functions, as well as how it can be practically deployed in an enterprise BYOD context to manage Bonjour services. To this end, step-by-step configuration guidance and verification commands are presented for both Cisco Unified Wireless Network Controllers (WLC 5508) and the Converged Access Switches and Controller (CT 3850/ WLC 5760).
Bonjour is Apple’s implementation of a suite of zero-configuration networking protocols and is supported on both Mac OS X devices (such as laptops and desktops), as well as on Apple iOS devices (such as iPhones and iPads). Bonjour is designed to make network configuration easier for users.
For example, consider enabling IP-based print services. Each printer needs a unique IP address, whether statically assigned or dynamically assigned (by a DHCP server). Since dynamically-assigned addresses can change, most printers are manually configured with a static address so that computers on the network can reach them using the same address every time. In this case, each client device must know the statically configured IP address of the printer(s) in order to use these. To make the process more user friendly, network administrators may configure DNS records so that clients can access printers by name, rather than by specific IP addresses. Even so, the clients must know the specific DNS name of each printer they are trying to access. Thus, the seemingly minor task of enabling IP-based printing can require significant client and server configuration. Additionally, in a home network environment, people who do not fit the traditional role of the network administrator often set up networks (e.g., families connecting their laptops and personal devices to the Internet over a shared router). As such, this level of configuration simply is not practical in such a setting.
Consider the same example in a network running Bonjour. Bonjour lets you connect a printer to your network without assigning it a specific IP address or manually entering that address into each computer. With zero-configuration networking, nearby computers can discover its existence and automatically determine the printer’s IP address. If that address is a dynamically assigned address that changes, they can automatically discover the new address in the future.
- File Sharing Services
- Remote Desktop Services
- Full screen Mirroring (Apple iOS v5.0+ for iPad2, iPhone4S, or later)
- iTunes Services:
Bonjour’s zero-configuration networking services benefit not only users (who will no longer have to assign IP addresses or host names to access network services), but also applications (as applications can leverage Bonjour to automatically detect required services or to interact with other applications to allow for automatic connection, communication, and data exchange, all without any user configuration).
- Addressing (allocating IP addresses to hosts)—Bonjour Addressing
- Naming (using names to refer to hosts instead of IP addresses)—Bonjour Naming
- Service discovery (finding services on the network automatically)—Bonjour Service Discovery
Bonjour solves the addressing problem of allocating IP addresses to hosts by leveraging self-assigned link-local addressing. Link-local addressing uses a range of addresses reserved for the local network and is achieved differently by IPv6 and IPv4:
- IPv6 includes self-assigned link-local addressing as part of the protocol
- IPv4 self-assigned addressing works by picking a random IP address in the link-local range and testing it. If the address is not in use, it becomes the local address. If it is already in use, the computer or other device chooses another address at random and tries again.
Any user or service on a computer or iOS device that supports link-local addressing benefits from this feature automatically. When a host computer joins a local network, it finds an unused local address and adopts it. No user action or configuration is required.
Bonjour leverages Multicast DNS (mDNS) for name-to-address translation, which sends DNS-format queries over the local network using an IP multicast address. Because these DNS queries are sent to a multicast address, no single DNS server with global knowledge is required to answer the queries. Each service or device can provide its own DNS capability—when it sees a query for its own name, it provides a DNS response with its own address.
Actually, Bonjour goes a bit further than basic mDNS functionality by including a responder that handles mDNS queries for any network service on the host computer or iOS device. This relieves an application of the need to interpret and respond to mDNS messages. Once a service is registered with the Bonjour process, Bonjour automatically advertises the availability of the service so that any queries for it are directed to the correct IP address and port number automatically.
Note Registration is performed using one of the Bonjour APIs. This functionality is available only to services running on the host OS X computer or iOS device. Services running on other devices, such as printers, need to implement a simple mDNS responder daemon that handles queries for services provided by that device (which is included on printers supporting the Apple AirPrint feature).
Bonjour also provides built-in support for the NAT port mapping protocol (NAT-PMP). If the upstream router supports this protocol, OS X and iOS applications can create and destroy port mappings to allow hosts on the other side of the firewall to connect to the provided services.
For name-to-address translation to work properly, a unique name on the local network is necessary. Unlike conventional DNS host names, the local name only has significance on the local network or LAN segment. A local name can be assigned much the same way as a self-assigned a local address: a name is chosen and if it is not already in use, it gets used. If it is unavailable, then the name can be modified slightly and re-tested for availability. For example, if a printer with the default name XYZ-LaserPrinter.local attaches to a local network with two other identical printers already installed, it tests for XYZ-LaserPrinter.local, then XYZ-LaserPrinter-2.local, then XYZ-LaserPrinter-3.local, which is unused and which becomes its name.
This section explains the Bonjour local “domain” and the naming rules for Bonjour service instances and service types. These service names are snooped by and presented within the Cisco WLC and as such are helpful for an administrator to understanding.
Bonjour protocols deal primarily with local link service advertisements. A host’s link-local network includes itself and all other hosts that can exchange packets without IP header data being modified (i.e., hosts sharing a single layer 2 domain/VLAN). In practice, this includes all hosts not separated by a router. On Bonjour systems, “local.” is used to indicate a name that should be looked up using an mDNS query on the local IP network.
Note that “local.” is not really a domain, but rather a pseudo-domain. It differs from conventional DNS domains in a fundamental way: names within DNS domains are globally unique; link-local domain names are not. As such, local names are useful only on the local network. In many cases this is adequate, as these provide a way to refer to network devices using names instead of IP numbers and of course they require less effort to coordinate and administer as compared to globally unique names.
Locally unique names are particularly useful on networks that have no connection to the global Internet, either by design or because of interruption, and on small, temporary networks, such as a pair of computers linked by a crossover cable or a few people playing network games using laptops on the wireless network of a home or cafe.
Bonjour service instance names are intended to be user-readable strings with descriptive names. Figure 1 illustrates the organization of the name of a Bonjour service instance. At the top level of the tree is the domain, such as “local.” for the local network. Below the domain is the registration type, which consists of the service type preceded by an underscore (_music) and the transport protocol, also preceded by an underscore (_tcp). At the bottom of the tree is the human-readable service instance name, such as Zealous Lizard's Tune Studio. The complete name is a path along the tree from bottom to top, with each component separated by a dot.
Table 1 shows a list of some Bonjour protocols by their names and service type strings.
The final element of Bonjour is service discovery. Service discovery allows applications to find all available instances of a particular type of service and to maintain a list of named services and port numbers. The application can then resolve the service hostname to a list of IPv4 and IPv6 addresses, as previously described.
The list of named services provides a layer of indirection between a service and its current DNS name and port number. Indirection allows applications keep a persistent list of available services and resolve an actual network address just prior to using a service. The list allows services to be relocated dynamically without generating a lot of network traffic announcing the change.
Service discovery in Bonjour is accomplished by “browsing.” An mDNS query is sent out for a given service type and domain, and any matching services reply with their names. The result is a list of available services to choose from.
This is very different from the traditional device-centric paradigm of network services, which describes services in terms of physical hardware. In a device-centric view, the network consists of a number of devices or hosts, each with a set of services. In a device-centric browsing scheme, a client queries the server for what services it is running, gets back a list (FTP, HTTP, print-services and so on), and decides which service to use. The interface reflects the way the physical system is organized. But this is not necessarily what the user logically wants or needs.
On the other hand, a service-centric paradigm is typically more logical and efficient from a user-perspective. Users typically want to accomplish a certain task, not query a list of devices to find out what services are running. It makes far more sense for a client to ask a single question, “What print services are available?” than to query each available device with the question, “What services are you running?” and sift through the results looking for printers. The device-centric approach is not only time-consuming, but it also generates a significant amount of irrelevant network traffic. In contrast, the service-centric approach sends a single query, generating only relevant replies.
Bonjour takes the service-oriented view. Queries are made according to the type of service needed, not the hosts providing them. Applications store service instance names, not addresses, so if the IP address, port number, or even host name has changed, the application can still connect. By concentrating on services rather than devices, the user’s browsing experience becomes more relevant and efficient.
Server-free addressing, naming, and service discovery have the potential to create a significant amount of excess network traffic, but Bonjour uses several mechanisms to reduce this traffic to a minimum to avoid unnecessary “chattiness”, including:
Bonjour uses a cache of mDNS records to prevent hosts from requesting information that has already been requested. For example, when one host requests, say, a list of print spoolers, the list of printers comes back via multicast, so all local hosts see it. The next time a host needs a list of print spoolers, it already has the list in its cache and does not need to reissue the query.
To prevent repeated answers to the same query, Bonjour service queries include a list of known answers. For example, if a host is browsing for printers, the first query includes no print services and gets, say, twelve replies from available print servers. The next time the host queries for print services, the query includes a list of known servers. Print servers already on the list do not respond.
Bonjour also suppresses duplicate responses in another way. If a host is about to respond, and notices that another host has already responded with the same information, the host suppresses its response.
When a host is browsing for services, it does not continually send queries to see if new services are available. Instead, the host issues an initial query and sends subsequent queries exponentially less often, for example: after 1 second, 3 seconds, 9 seconds, 27 seconds, and so on, up to a maximum interval of one hour.
This does not mean that it can take over an hour for a browser to see a new service. When a service starts up on the network, it announces its presence a few times using a similar exponential back-off algorithm. This way, network traffic for service announcement and discovery is kept to a minimum, but new services are seen very quickly.
However it should be noted that the mDNS addresses used by Bonjour are link-local multicast addresses and are only forwarded within the local Layer 2 domain, as link-local multicast is meant to stay local by design. Furthermore, routers cannot even use multicast routing to redirect the mDNS queries, because the time-to-live (TTL) of these packets is set to 1.
Bonjour was originally developed with home networks in mind. As such, since most home networks consist of a single Layer 2 domain, this link-local limitation of mDNS rarely posed any practical deployment constraints. However in an enterprise context, where large numbers of (wired and wireless) Layer 2 domains exist, this limitation severely handicaps Bonjour functionality, as Bonjour clients would only see locally-hosted services and would not be able to see or connect to services hosted on other subnets. This link-local multicast limitation of Bonjour mDNS is illustrated in Figure 2.
To address this limitation and to facilitate BYOD functionality on enterprise networks, Cisco released a Bonjour Gateway feature in WLC 7.4+ software. The Bonjour Gateway feature (technically speaking a mDNS gateway feature, but most relevantly applied to Bonjour) snoops and caches all Bonjour service advertisements across multiple VLANs and can be configured to (selectively) reply to Bonjour queries. Figure 3 through Figure 5 illustrate the operation of the Bonjour Gateway.
In Figure 3, the Bonjour Gateway listens/snoops all Bonjour advertisements.
Next, the Bonjour Gateway caches all these service advertisements, as shown in Figure 4.
Note Incidentally, CUWN WLCs support up to 64 services and 100 service providers per service type. Each service provider is registered in the WLC as its domain name. Additionally, each Bonjour service has an advertised TTL (which is different from a packet’s TTL) and the controller asks the device for an update at 85% of this TTL.
In addition to listening to service advertisements, the WLC is always listening for client queries for services, as illustrated in Figure 5.
Clients that request locally-hosted services will receive unicast replies from the service provider; however clients that request services that may be hosted on other VLANs will receive unicast responses from the WLC, as shown in Figure 6.
And finally, the Bonjour Gateway service can serve to further optimize Bonjour traffic by unicasting replies directly to clients requesting a given service (as opposed to multicasting replies like some competitive solutions), making more efficient use of network resources, as shown in Figure 7.
A key functional advantage of the Bonjour Gateway is that it can be configured to selectively reply to Bonjour service requests, thus allowing for administrative control of Bonjour services within the enterprise. Bonjour policies can be applied on the following basis:
- Per WLAN (on CUWN Controllers only)
- Per Interface/Interface-Group (on CUWN Controllers only)
- Per VLAN (on CUWN Controllers and Converged Access Controllers/Switches)
These Bonjour service policy options are illustrated in Figure 8.
Consider a few examples of how such Bonjour service policies may be deployed. For instance, in an BYOD enterprise context, you can configure Bonjour policies such that employees can take advantage of Bonjour services that enhance productivity (such as AirPrint, AirPlay, and File Sharing), but block entertainment-oriented Bonjour services (such as iTunes Sharing).
Additionally, stricter limitations could be placed on Guest WLANs. For example, inter-domain Bonjour services could be limited to AirPlay only—such that guest devices may be allowed to connect to (wired or wireless) AppleTVs that reside on the production network—so that guests could share presentations, videos, demonstrations, etc.
These example Bonjour service policies for an enterprise BYOD deployment context are illustrated in Figure 9.
It is important to note that these Bonjour service policy examples are not a one-size-fits-all solution. The policy-specifics will likely vary according to deployment contexts. As a second example consider a college/university deployment context. In this example, assume separate WLANs for teachers and students. Teachers would likely have all Bonjour productivity-oriented services enabled, such as AirPrint, AirPlay, and File Sharing. However you may wish to limit AirPlay on student networks, as this may prevent significant volumes of traffic traversing different WLANs as students may host full-length HD movies on one network while streaming them to devices on another. Similarly, Time Capsule traffic may be another service to limit from spanning WLANs—again due to the significant traffic loads these typically entail. However, consideration may be extended students by permitting iTunes Music Sharing (as music files are significantly smaller than videos or Time-Capsule backups).
These example Bonjour service policies for a university BYOD deployment context are illustrated in Figure 10.
- Wireless-to-Wired Bonjour Gateway Service Policies—The primary use case is enabling wireless BYOD devices to print to wired AirPrint printers.
- Wireless-to-Wireless Bonjour Gateway Service Policies—Enables Bonjour services to be shared among devices in separate WLANs; an example use case would be to allow guest devices to access wireless AppleTVs to share presentations (even though these devices may reside in different WLANs).
- Multi-node Bonjour Gateway Service Policies—Enables Bonjour services to be selectively shared across multiple network nodes (this option is available for Converged Access platforms only).
- Interfaces/Interface-Groups (Only CUWN Controllers)
- WLANs (Only CUWN Controllers)
- VLANs (Both CUWN Controllers and Converged Access Controllers/Switches)
For CUWN examples, the examples that follow utilize a variety of deployment options. Furthermore, design configuration are presented both via the Cisco WLC GUI and the Cisco WLC CLI. CLI examples show both the general syntax of a command (which is highlighted in blue) and the specific variation needed in the design example (which is highlighted in red).
In this primary Bonjour Gateway use case, wireless BYOD employee devices are permitted to access AirPrint-enabled printers that are deployed on separate wired networks. Incidentally, this design will also support wireless printing from wireless clients across separate WLANs (only on CUWN Controllers).
A prerequisite of this design is that the wired VLANs hosting AirPrint printers must be trunked to the Cisco WLC controller, as shown in Figure 11.
Multiple design and configuration options exist to enable Bonjour service policies and in the following examples different approaches will be used to highlight some of these options. In addition, Bonjour Gateway feature configurations are presented for both the Cisco Unified Wireless Networking (CUWN) Centralized WLC deployment model and the Converged Access deployment model in the respective sections below.
These steps are shown in Figure 12.
The corresponding Cisco WLC CLI for globally enabling mDNS snooping is shown in Example 1.
The mDNS snooping query interval can be tuned with the command shown in Example 2 (again the range is 10 to 120 minutes). Example 2 shows both the general version of this command and the specific syntax to set the mDNS query interval to 10 minutes.
These mDNS configuration commands can be verified by the show network summary command output, as illustrated in Example 3.
Figure 13 shows the Apple File Sharing Protocol (AFP) service being added to the default mDNS profile.
Bonjour services can be added to the default (or non-default) profiles with the command shown in Example 4. The Profile Name of the default mDNS profile is “default-mdns-profile”.
This is shown in Figure 14 where the AirPlay service (the service that allows for iTunes music to be streamed to a remote Apple Airport Express device, which in turn can supply an audio signal of the music to speakers) is removed from the default mDNS profile.
Bonjour services can also be removed from the default (or non-default) profiles with the command shown in Example 5.
The addition/removal of services to a mDNS profile can be verified by the show mdns profile command, which can either show a summary of configured profiles or a detailed view of a specific profile, as shown in Example 6 and Example 7, respectively.
- Management interface (static and configured at setup time; mandatory)
- AP-manager interface (static and configured at setup time; mandatory)
- Virtual interface (static and configured at setup time; mandatory)
- Service-port interface (static and configured at setup time; optional)
- Dynamic interface (user-defined)
In this case, it is assumed that the ua28-wlc5508-1-v2 interface is applied to the BYOD_Employee WLAN (in line with the recommendations in Chapter 9, “BYOD Wireless Infrastructure Design”), as shown in Figure 15. If this is not the case, then the policies should be applied to whatever (static or dynamic) interface is associated with the WLAN. This association is verified by selecting the WLANs heading bar and then selecting the WLAN number that corresponds to the BYOD_Employee WLAN.
As Figure 16 shows (in this case) the ua28-wlc5508-1-v2 interface corresponds to VLAN 40, which is where the wired AirPrint printer(s) reside. Bonjour service advertisements from these printers will now be shared with other WLANs/VLANs.
The Default mDNS profile can be added to the interface associated with the WLAN with the commands shown in Example 8.
The mDNS profile attached to an interface can be verified by the command show interface detailed interface-name, as shown in Example 9. Alternatively, if the mDNS profile is attached to an interface-group, then the show command would be show interface group detailed interface-group-name.
If wireless multicast is enabled on the switch (which is the default setting), then wireless clients on the same client VLAN are able to discover Bonjour services even when mDNS configuration is not enabled, which will prevent administrative control over the advertisement of these policies. Therefore it is recommended to disable this default behavior with the no wireless mdns-bridging command, as shown in Example 10.
On the Converged Access platforms (WLC5760 and Catalyst 3850), the first step to configuring the Bonjour Gateway feature is to create a service policy to allow all mDNS traffic which is to be applied globally.
To enable the mDNS gateway feature on Converged Access platforms, create a mDNS service-list and apply it globally, as shown in Example 11, where a service-list has been configured to allow all types of mDNS traffic.
Note This service-list can also be used to restrict specific mDNS traffic types, as is shown in Step 3—Configure and Globally Apply a mDNS Querier.
An optional mDNS querier can also be configured on the Converged Access platforms to permit only specific DNS queries. This may be useful in enterprise environments to restrict specific types of services over the network.
In Example 12, a mDNS querier is configured (via a service-list) to permit only AirPrint, IP Printing, and Scanning queries and is then applied globally.
Example 13 shows an edited mDNS service list that permits only AirPrint and directory services.
It is important to discuss that by enabling mDNS gateway functionality globally, all VLANs will have the global service policy enabled. However, individual VLANs can also be configured with individual service policies to permit only specific types of mDNS traffic. This is useful in an enterprise environment where a printer may be on one VLAN, but its services should be available to specific clients on a different VLAN.
Example 14 shows how mDNS policies can be applied on a per-VLAN basis. Specifically, all mDNS traffic to be passed and cached on VLAN 10 (via the service-list configured in Step 1—Disable mDNS Bridging for Wireless Clients); however only AirPrint. IP Printing, and Scanning services (configured in Step 3—Configure and Globally Apply a mDNS Querier) are permitted over VLAN 11.
To verify that the mDNS cache is being populated with the required services, use the show mdns cache command (shown in Example 12) which will list all the services in the mDNS cache and the VLAN on which they have been detected.
In this secondary Bonjour Gateway use case, wireless guest devices are permitted to access Apple TV devices (using AirPlay) so that guests may share presentations, video, or other content with employees. Incidentally, Apple TVs, like some AirPrint printers, may be connected via either wired or wireless connections; this design supports both options. However in this case, assume the Apple TV is residing in the BYOD Personal Devices WLAN, as shown in Figure 17.
2. Click the New button at the top-right, as shown in Figure 18.
3. Give the new profile a name and click the Apply button, as shown in Figure 19.
The corresponding Cisco WLC CLI for creating a new mDNS profile is shown in Example 15, which creates a new mDNS profile named “Guest-mDNS-Profile”.
Newly created mDNS profiles will be displayed by the show mdns profile summary verification command, as shown in Example 16.
In this particular use case, only the AirPlay service will be offered to BYOD guest devices. Therefore the Bonjour AirPlay service needs to be added to the new mDNS Profile, which is done by performing the following:
2. Select the desired Bonjour service(s) from the Services List drop-down list and click the Add button, as shown in Figure 20.
The corresponding Cisco WLC CLI for adding Bonjour services to a profile is shown in Example 17.
Services within a mDNS profile can be verified by the show mdns profile detailed command, as presented in Example 18.
1. Click the WLANs heading-bar and select the desired WLAN (in this case, the BYOD_Guest WLAN, as shown in Figure 21).
The mDNS settings of a WLAN can be verified by the show wlan wlan-id verification command, as shown in Example 21.
- Step 1—Disable mDNS Bridging for Wireless Clients
- Step 2—Configure and Globally-Apply a Service Policy for mDNS Traffic
- Step 3—Configure and Globally-Apply a mDNS Querier
- Step 4—Edit mDNS Service Policies
- Step 5—Apply mDNS Service Policies to a VLAN
Each of these steps is described, however for brevity these steps are combined into a single configuration example, shown in Example 22.
Note As previously noted, applying mDNS policies on a per-WLAN basis is not supported on Converged Access platforms, therefore the mDNS policies are applied to the Guest VLAN interface in this adapted example.
Note While Bonjour services on Guest VLANs are restricted to AirPlay, other Bonjour services—such as AirPrint, IP Printing, and Scanning—are permitted in other parts of the network. As such, the global querier will include all these services.
Multi-node Bonjour Gateway service policies enable Bonjour services to be selectively shared across multiple network nodes. Furthermore, this option is available for Converged Access platforms only. This deployment model allows Bonjour services to be redistributed and advertised to other network devices.
In this use case, a multi-node mDNS deployment model scenario consists of a Catalyst 4500 switch in the distribution layer and three separate Catalyst 3850 switches in the access layer. As a practical example, let us consider three different areas in a school environment, each of which has various Bonjour-enabled devices deployed within them:
- A Classroom using access-switch C3850-1
- An Office using access-switch C3850-2
- A Social area using access-switch C3850-3
- The Apple-TV in the classroom does not need to be advertised outside the classroom.
- The Printer and File Servers in the Office area need to have their Bonjour services advertised/redistributed to the other nodes in the network, however the Apple TV located in this area needs to remain local to this area.
- The Music Player in the Social Area may be advertised to all the other nodes in the school network.
The network and rules for this use-case are summarized in Figure 23.
In addition to the GUI and CLI configuration-verification screenshots and commands that have been highlighted in the previous sections, Cisco WLC software has some additional options for verifying Bonjour Gateway operation, which we now discuss.
For instance, a summary of all mDNS records can be shown by clicking the CONTROLLER heading-bar, expanding the mDNS link on the lower left, and then clicking Domain Names, as shown in Figure 24.
A summary of mDNS records can also be provided via the CLI with the command show mdns domain-name-ip summary, as shown in Example 27.
Also, clicking on any service listed within an mDNS profile will display a mDNS Service>Detail screen that will display device-level details—including MAC address, VLAN, and network-type (wired or wireless) for any and all devices providing that Bonjour service. For example, Figure 25 shows that the Apple TV service is available both via the wired and wireless networks.
Device-level mDNS service detail is also available via the CLI using the command show mdns service detailed mdns-service-name, as demonstrated in Example 28.
Additionally, the CLI allows for a summary of mDNS services to be displayed via the show mdns service summary command, as shown in Example 29.
Finally, it bears mentioning that third-party tools are also available to verify mDNS operations. For example, Figure 26 shows Tildesoft’s “Bonjour Browser” displaying mDNS details for the Epson wired AirPrint printer.
While the configuration and verification of the Bonjour Gateway feature remains the same for these scenarios, it may be helpful for network administrators to understand how this feature operates in these contexts.
In guest anchoring scenarios, the guest WLAN is able to see Bonjour services advertised to the anchor controller. This is because the Bonjour queries and advertisements are sent inside the Control and Provisioning of Wireless Access Points (CAPWAP) tunnel, as shown in Figure 27.
Bonjour Gateway with Layer 3 roaming works across Ethernet over IP (EoIP) tunnels to ensure that users moving among access points (APs) on different controllers continue to see the devices they saw on the original controller. The Bonjour services on the anchor controller are displayed to the client, including both wired and wireless devices, as shown in Figure 28.
For centrally-switched WLANs, the behavior for Bonjour is the same as if the AP was in local mode. In this case, Bonjour queries from the client are sent to the controller and Bonjour responses from the controller are sent back to the AP in the unicast CAPWAP tunnel. This means FlexConnect APs will not require “Multicast-Unicast” mode to support Bonjour.
Note Customers running FlexConnect in branches can also run Bonjour Gateway functionality over their wired network infrastructure (Cisco switches and/or routers). For additional details on such design options, see: http://www.cisco.com/go/mdns and http://www.cisco.com/en/US/docs/wireless/controller/technotes/5700/software/release/ios_xe_33/service_discovery_gateway_DG/b_service_discovery_gateway_DG.html.
This paper overviewed Apple’s Bonjour protocol—a zero-configuration protocol for advertising, discovering, and connecting to network services—and how it can be effectively managed within a BYOD enterprise context.
The design limitation of Bonjour’s use of link-local multicasting was discussed, showing how it limited the usefulness of the protocol to only a single Layer 2 domain. To enable the use of Bonjour in (multi-WLAN/VLAN) BYOD enterprise networks, the Cisco WLC Bonjour Gateway was introduced. Next, an overview of the operation of the Bonjour Gateway feature was provided, showing how it can be used to snoop, cache, and proxy-respond to Bonjour service requests. Additionally, it was shown how these responses could be selectively enabled and disabled, allowing for administrative policy-based control of Bonjour services.
- Printing from wireless devices to wired printers.
- Sharing Bonjour services between wireless devices in different WLANs.
Step-by-step configuration guidance was presented for each scenario, using slightly different approaches to highlight the various configuration options available. Each step was presented for not only the Cisco WLC GUI configuration and verification, but also for the Cisco WLC CLI.
Additional verification options were also highlighted, as well as how the Bonjour Gateway operates in various advanced scenarios, including guest anchoring, Layer 3 roaming, and FlexConnect deployments.
- Cisco Wireless LAN Controller Configuration Guide, Release 7.4—Configuring Multicast Domain Name System
- Cisco Catalyst 3850 Switches—IOS XE 3.3SE Release Configuration Guide—Configuring the Service Discovery Gateway
- Cisco WLC Bonjour Gateway Deployment Guide