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Before configuring multicast routing over GRE, you should be familiar with the concepts of IP Multicast Routing Technology and GRE Tunneling.
The following are the restrictions for configuring multicast routing over GRE tunnel:
IPv6 multicast over GRE tunnel is not supported.
The total number of supported multicast routes (mroutes) is 2000, across all tunnels.
Bidirectional PIM is not supported.
Multicast routing should be configured on the first hop router (FHR), the rendezvous point (RP) and the last hop router (LHR) to support multicast over the GRE tunnel.
On Catalyst 9500 series switches, the tunnel source can be a loopback, physical, or L3 EtherChannel interface.
No feature interactions such as IPSec, ACL, Tunnel counters, Crypto support, Fragmentation, Cisco Discovery Protocol (CDP), QoS, GRE keepalive, Multipoint GRE, etc. are supported on the GRE Tunnel.
Note | Beginning in Cisco IOS XE Denali 16.3.1, multicast routing and NHRP are supported with GRE Tunneling. NHRP can optionally be configured along with the multicast configuration on the tunnel interface to facilitate dynamic discovery of tunnel end points. Please see NHRP for configuring NHRP on a tunnel interface. |
You can configure a GRE tunnel to transport IP multicast packets between a source and destination that are connected by a medium that does not support multicast routing.
The following example shows multicast-routing between a Catalyst switch through a GRE tunnel.
In the figure above, the multicast source (10.1.1.1) is connected to Catalyst Switch-1 and is configured for multicast group 239.1.1.20. The multicast receiver (10.2.2.3) is connected to Catalyst Switch-2 and is configured to receive multicast packets for group 239.1.1.20. Separating Switch-1 and Switch-2 is an IP cloud, which is not configured for multicast routing.
A GRE tunnel is configured between Switch-1 to Switch-2 sourced with their loopback interfaces. Multicast-routing is enabled on Switch-1 and Switch-2. The ip pim sparse-dense-mode command is configured on tunnel interfaces to support PIM in either the sparse or dense modes. Sparse-dense mode configuration on the tunnel interfaces allows sparse-mode or dense-mode packets to be forwarded over the tunnel depending on rendezvous point (RP) configuration for the group.
Device(config)# ip multicast-routing Device(config)# interface Loopback0 //Tunnel source interface Device(config-if)# ip address 2.2.2.2 255.255.255.255 Device(config)# interface Tunnel 10 //Tunnel interface configured for PIM traffic Device(config-if)# ip address 192.168.24.1 255.255.255.252 Device(config-if)# ip pim sparse-dense-mode Device(config-if)# ip nhrp map 192.168.24.3 4.4.4.4 //NHRP may optionally be configured to dynamically discover tunnel end points. Device(config-if)# ip nhrp map multicast 4.4.4.4 Device(config-if)# ip nhrp network-id 1 Device(config-if)# ip nhrp nhs 192.168.24.3 Device(config-if)# tunnel source Loopback0 Device(config-if)# tunnel destination 4.4.4.4 Device(config)# interface GigabitEthernet 0/0/0 //Source interface Device(config-if)# ip address 10.1.1.2 255.255.255.0 Device(config-if)# ip pim sparse-dense-mode
Device(config)# ip multicast-routing Device(config)# interface Loopback0 //Tunnel source interface Device(config-if)# ip address 4.4.4.4 255.255.255.255 Device(config)# interface Tunnel 10 //Tunnel interface configured for PIM traffic Device(config-if)# ip address 192.168.24.2 255.255.255.252 Device(config-if)# ip nhrp map 192.168.24.4 2.2.2.2 //NHRP may optionally be configured to dynamically discover tunnel end points. Device(config-if)# ip nhrp map multicast 2.2.2.2 Device(config-if)# ip nhrp network-id 1 Device(config-if)# ip nhrp nhs 192.168.24.4 Device(config-if)# ip pim sparse-dense mode Device(config-if)# tunnel source Loopback0 Device(config-if)# tunnel destination 2.2.2.2 Device(config)# interface GigabitEthernet 0/0/0 //Receiver interface Device(config-if)# ip address 10.2.2.2 255.255.255.0 Device(config-if)# ip pim sparse-dense-mode
The following sections provide references related to customizing IGMP.
Related Topic |
Document Title |
---|---|
For complete syntax and usage information for the commands used in this chapter. |
See the IP Multicast Routing Commands section of the Command Reference, Cisco IOS XE Everest 16.5.1a (Catalyst 9500 Series Switches) ) |
Cisco IOS commands |
Standard/RFC |
Title |
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None |
N/A |
MIB |
MIBs Link |
---|---|
No new or modified MIBs are supported by these features, and support for existing MIBs has not been modified by these features. |
To locate and download MIBs for selected platforms, Cisco IOS XE releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Release |
Modification |
---|---|
Cisco IOS XE Everest 16.5.1a |
This feature was introduced. |