Configuration and Concepts
The Bonjour protocol operates on service announcements and service queries, which allow devices to ask and advertise specific applications such as:
• Printing Services
• File Sharing Services
• Remote Desktop Services
• iTunes File Sharing
• iTunes Wireless iDevice Syncing
These service announcements and queries are link-local multicast addresses which are only forwarded on the local Layer 2 (L2) domain, since link-local multicast is meant to stay local by design.
In Cisco Unified and NGWC wireless deployments, wireless multicast is not forwarded with default configurations.
Successful implementation requires one of three configurations to be implemented in order to provide Bonjour services to Cisco Wireless clients:
1) Configure WLC multicast
- Bonjour will only function within vlans, wired and wireless
Cisco Wireless LAN Controller Configuration Guide, Release 7.4 – Configuring Multicast
Wireless LAN Apple Bonjour Deployment Guide
Understanding WLC Multicast
2) Implement the WLC Bonjour (mDNS) Gateway Feature
- Bonjour will function Inter-vlan wireless to wireless only
The mDNS Gateway Feature will provide wireless inter-vlan name and service resolution, but L3 unicast routing must also be functional between the clients for inter-vlan Bonjour dependent applications to function.
- If configured, non-Bonjour multicast will function independently with the mDNS gateway enabled
- Bonjour will function wired to wireless:
WLC Code 7.4: Intra-vlan only
WLC Code 7.5: Inter-vlan with mDNS AP configured
- Referred to as 'Service Discovery Gateway' on NGWC (3850/5670) platforms
- Feature initially introduced:
CUWN 7.4.100
Release Notes for Cisco Wireless LAN Controllers and Lightweight Access Points for Release 7.4.100.0 – What’s New in this Release?
Bonjour Gateway Deployment Guide 7.4
Bonjour Gateway Wireless LAN Controller Deployment Guide, Release 7.5
NGWC 3.3.0SE
Release Notes for Cisco 5700 Series Wireless LAN Controller, Cisco IOS XE Release 3.3.xSE – What’s new in Cisco IOX XE Release 3.3.0SE
Configuring the Service Discovery Gateway
Service Discovery Gateway Deployment Guide, Cisco IOS-XE Release 3.3
3) Flexconnect local switching or Autonomous mode Access Points
- Unified Flexconnect Access Points servicing wlans enabled for 'Flexconnect Local Switching' do not forward client traffic to the WLC via Capwap tunnel, eliminating multicast configuration considerations. Flexconnect Access Points send flexconnect locally switched wlan traffic directly to their connected switch. L2 mDNS traffic from the Flexconnect AP should be treated as traffic from another switch, therefore mDNS should function within the local Vlan.
- Traffic handling and considerations for Autonomous Access Points are the same as the previously referenced Flexconnect Local Switching client traffic.
- A L3 IGMP router may be required in some topologies to sustain reliable L2 multicast functionality. Refer to the following document for further information:
Multicast Does Not Work in the Same VLAN in Catalyst Switches
Common Issues
1) With traditional multicast, Bonjour name resolution will not work on anchored Wireless Lan Controller Wlans (eg guest wlan anchored to anchor/dmz controller-- see CSCtr26626 ).
This is due to the fact that multicast traffic is not supported over guest tunnels, even if multicast is enabled on the Cisco Unified Wireless Network: http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob41dg/ch10GuAc.html#wp1057543
Bonjour service resolution with anchored wlans will function with the WLC Bonjour (mDNS) gateway feature. Configuration is required on anchor and foreign controllers.
2) Some Bonjour clients may not send IGMP reports for the corresponding mDNS address. If IGMP snooping is enabled on the relevant Wireless Lan Controller, Bonjour will not function until at least one wireless client sends an IGMP report for the mDNS group.
This issue is only applicable to multicast dependent implementations, as the mDNS Gateway feature does not rely on IGMP to function.
3) Number of Apple TVs limitation in iOS devices:
Whenever there are more than 63 Apple TVs being advertised, the iOS devices (iPad and iPhones) won’t be able to mirror them correctly, there is no way to rule which 63 devices will be listed.
This limitation is due to the iOS's mDNS Route Picker which can only handle 63 entries. There is no hard rule for which 63 will be listed.
The new LSS feature on 7.5 can help this by segregating the Apple TVs into groups, http://www.cisco.com/en/US/docs/wireless/technology/bonjour/7.5/Bonjour_Gateway_Phase-2_WLC_software_release_7.5.html#wp44429
If the customer cannot upgrade to 7.5 they will need to get back to multicast and segregate the Apple TVs by VLANs.
Known Bugs
Current Issues:
CSCud33073 mDNS snooping is enabled for flexlocal sw enabled WLAN after WLC upgrade
+Resolved in 7.5.102.0
CSCue05421 iTunes Home Sharing is not snooped by controller
+Not yet resolved
CSCue22334 mDNS LSS is not working due to Wrong AP Base MAC returned from RRM DB
+Resolved in 7.5.102.0
CSCue90227 mDNS Gateway doesn't advertise wireless device services to wired network
+Not yet resolved
CSCuf69032 Bonjour LSS feature not working
+Resolved in forthcoming 8.0 code
CSCue72667 8500 or vWLC doesn't include 4th SP data in response
+Resolved in 7.5.102.0
Issues Resolved in 7.4.121.0 or later:
CSCud44827 WLC drops mdns packets when dns-sd & nsec records are not present
CSCud78560 WLC updates mDNS TTL with junk values when disable/enable snooping
CSCuj36260 cannot disable mDNS snooping on WLAN with local switching after upgrade
