(Cisco Controller) > debug mdns all enableĬisco Controller) >*emWeb: Feb 22 16:24:18.203: bgSetBonjourAccessPolicy :1192 Bonjour AccessPolicy status is already in requested state Disabled Here the snippet only shows query from management interface. The debugs reflect the same thing as seen in the captures. This capture is the query packet in detail as shown in the image. This mode is very inefficient and is not recommended. In this mode, the controller unicasts every multicast packet to every AP associated to the controller. Note: If multicast routing is not enabled on the wired for wlc and AP management vlan, then AP multicast mode must be set to unicast. As the devices are in different vlans, you needs to have multicast routing enabled for vlan 1 and 239 on the wired for this to work. Remember in this setup the WLC is a 2504 in vlan 1 and the AP is in vlan 231. The address 239.100.100.100 (this is not static, this is what you configured in the next example) only appears in the capwap header between the WLC and the APs, the wireless clients never sees anything of it (but it can see the inner original mdns packet) as shown in the image. WLC forwards the query to this group, APs receive it and send it over the air. The APs join this multicast group and listen on it. Now, where does this multicast IP 239.100.100.100 come from? On the WLC, Access Point (AP) multicast mode ( controller > general) was set to multicast with multicast group address as 239.100.100.100 (it is just an example, any ip in the 239 range). Since this query is over the wireless, capwap header is added to the packet with outer source IP still to be that of management but the destination is multicast IP 239.100.100.100 as shown in the image. The inner packet shows WLC query to 224.0.0.251 from management interface. Packet 83 shows that WLC sends a query over the wireless. In this capture at WLC switch port, packets 80, 81 and 82 show WLC sends a query to 224.0.0.251 over the wired network with source IP of the management (10.48.39.142) and dynamic interfaces(192.168.232.11 and 192.168.239.8) as shown in the image. When mDNS is enabled globally, the controller sends mDNS queries to 224.0.0.251 for all the services on wired (management and dynamic interfaces) and wireless network. Additionally, it can contain one or more subtype identifiers. AppleTV service uses: _airplay._tcp.local. A service type always contains the service name and the protocol. Service strings are used to match service instances to service queries. WLC listens to these default services if you does not have a customized mDNS profile created as shown in the image.Įach of these services has a service string associated with it. These steps are described as follows: Step 1. There are basic four steps which take place when mDNS runs on a Cisco WLC. This way you can have the sources and clients in different subnets. For example, Apple TV and responds back to Bonjour clients when they ask/request for a service. The WLC listens for Bonjour services, caches these Bonjour advertisements (AirPlay, AirPrint, and so on) from the source/host. In order to address this issue, the Cisco Wireless LAN Controller (WLC) acts as a Bonjour Gateway. This meant that all the service providers/sources (which advertise the service) and Bonjour clients(which ask for service) had to be in the same subnet. Routers cannot use multicast routing to redirect the traffic because the time to live (TTL) is set to 1. The address used by the Bonjour protocol is link-local multicast address and therefore is only forwarded to the local L2 network. This protocal uses mDNS on UDP port 5353. Each query or advertisement is sent to the Bonjour multicast address ipv4 224.0.0.251 (ipv6 FF02::FB). The Bonjour protocol operates on service announcements and service queries. Background Informationīonjour protocol is an Apple service discovery protocol which locates devices and sevices on a local network with the use of multicast Domain Name System (mDNS) service records. If your network is live, ensure that you understand the potential impact of any command. All of the devices used in this document started with a cleared (default) configuration. The information in this document was created from the devices in a specific lab environment. The information in this document is based on these software and hardware versions: Basic knowledge of how to configure mDNS on WLC.Prerequisites RequirementsĬisco recommends that you have knowledge of these topics: This document describes the implementation of the Bonjour protocol on the wireless controller and provides guidelines to help troubleshoot issues.
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