•
Packets with mDNS multicast IP and multicast MAC are sent on a multicast CAPWAP tunnel, if
multicast-multicast mode is enabled. A multicast CAPWAP tunnel is a special CAPWAP tunnel used
for reducing the number of copies of multicast packet that are required to be generated for each AP
CAPWAP tunnel. Sending packets on the multicast CAPWAP tunnel requires the outer IP header to be
destined to the multicast CAPWAP tunnel's address, which all APs are subscribed to.
•
All mDNS packet handling is done at a foreign switch for roamed clients. A foreign switch is the new
switch that a roamed wireless client is actually attached to, which is called the point of attachment.
Service Discovery Gateway
The Service Discovery Gateway feature enables multicast Domain Name System (mDNS) to operate across
Layer 3 boundaries (different subnets). An mDNS gateway provides transport for service discovery across
Layer 3 boundaries by filtering, caching, and redistributing services from one Layer 3 domain (subnet) to
another. Prior to implementation of this feature, mDNS was limited in scope to within a subnet because of
the use of link-local scoped multicast addresses. This feature enhances Bring Your Own Device (BYOD).
Related Topics
Configuring the Service List (CLI), on page 279
Example: Creating a Service-List, Applying a Filter and Configuring Parameters, on page 288
Enabling mDNS Gateway and Redistributing Services (CLI), on page 283
Example: Specify Alternative Source Interface for Outgoing mDNS Packets, on page 287
Example: Redistribute Service Announcements, on page 287
Example: Disable Bridging of mDNS Packets to Wireless Clients, on page 288
Example: Enabling mDNS Gateway and Redistributing Services, on page 288
Example: Global mDNS Configuration, on page 289
Example: Interface mDNS Configuration, on page 289
mDNS Gateway and Subnets
You need to enable an mDNS gateway for service discovery to operate across subnets. You can enable mDNS
gateway for a device or for an interface.
You need to configure service routing globally before configuring at the interface level.
Note
After the device or interface is enabled, you can redistribute service discovery information across subnets.
You can create service policies and apply filters on either incoming service discovery information (called
IN-bound filtering) or outgoing service discovery information (called OUT-bound filtering).
If redistribution is enabled globally, global configuration is given higher priority than interface configuration.
Note
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
OL-29890-01
277
Configuring the Service Discovery Gateway
Service Discovery Gateway
