Table Of Contents
Unidirectional Link Routing Commands
ip multicast default-rpf-distance
Unidirectional Link Routing Commands
Use the commands in this chapter to configure and monitor unidirectional link routing. For configuration information and examples of unidirectional link routing, refer to the "Configuring Unidirectional Link Routing" chapter of the Cisco IOS IP and IP Routing Configuration Guide.
ip igmp helper-address (UDL)
To configure Internet Group Management Protocol (IGMP) helpering as required for IGMP unidirectional link routing (UDLR), use the ip igmp helper-address (UDL) interface configuration command. To disable such report forwarding, use the no form of this command.
ip igmp helper-address udl type number
no ip igmp helper-address
Syntax Description
Defaults
No forwarding occurs.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command is required on a downstream router on each interface connected to a potential multicast receiver. The command allows the downstream router to helper IGMP reports received from hosts to an upstream router connected to a unidirectional link associated with the configured type and number arguments.
Examples
The following example configures a helper address on a downstream router:
ip multicast-routing!! Interface that receiver is attached to, configure for IGMP reports to be! helpered for the unidirectional interface.!interface ethernet 0description Forward IGMP reports from this interface to UDL querierip address 14.0.0.2 255.0.0.0ip pim sparse-dense-modeip igmp helper-address udl serial 0Related Commands
ip igmp unidirectional-link
To configure an interface to be unidirectional and enable it for Internet Group Management Protocol (IGMP) unidirectional link routing (UDLR), use the ip igmp unidirectional-link interface configuration command. To disable the unidirectional link, use the no form of this command.
ip igmp unidirectional-link
no ip igmp unidirectional-link
Syntax Description
This command has no arguments or keywords.
Defaults
No unidirectional link routing occurs.
Command Modes
Interface configuration
Command History
Usage Guidelines
One example of when you might configure this command is if you have traffic traveling via a satellite.
If you have a small number of receivers, another way to achieve UDLR is to configure a UDLR tunnel. See the tunnel udlr receive-only and tunnel udlr send-only commands.
Examples
The following example configures an upstream router with UDLR on serial interface 0:
ip multicast-routing!! Unidirectional link!interface serial 0description Unidirectional to downlink-rtrip address 10.0.0.1 255.0.0.0ip pim sparse-dense-modeip igmp unidirectional-linkno keepaliveRelated Commands
ip multicast default-rpf-distance
When configuring Internet Group Management Protocol (IGMP) unidirectional link routing, to change the distance given to the default Reverse Path Forwarding (RPF) interface, use the ip multicast default-rpf-distance global configuration command. To restore the default value, use the no form of this command.
ip multicast default-rpf-distance distance
no ip multicast default-rpf-distance
Syntax Description
Defaults
The distance default value is 15.
Command Modes
Global configuration
Command History
Usage Guidelines
This command is optional. If you want to receive all multicast traffic from all sources on the unidirectional link, as long as 15 is the lowest distance, you need not change the value of 15.
The default RPF interface is selected when an IGMP Query is received on a unidirectional link and indicates to the router all sources will RPF to the unidirectional link interface.
Any explicit sources learned by routing protocols will take preference as long as their distance is less than the distance argument configured with the ip multicast default-rpf-distance command.
You might consider changing the default value for one of the following reasons:
•
To make IGMP prefer the unidirectional link, configure a value less than existing routing protocols.
•
Examples
The following example configures a distance of 20:
ip multicast default-rpf-distance 20Related Commands
show ip igmp udlr
To display unidirectional link routing (UDLR) information for directly connected multicast groups on interfaces that have a unidirectional link helper address configured, use the show ip igmp udlr EXEC command.
show ip igmp udlr [group-name-or-address | type number]
Syntax Description
group-name-or-address
(Optional) Name or address of the multicast group for which to show UDLR information.
type number
(Optional) Interface type and number for which to show UDLR information.
Command Modes
EXEC
Command History
Usage Guidelines
This command displays which groups are being forwarded and received over the unidirectional link.
On the upstream router, this command shows which interface is a UDL interface and which IP multicast groups are being forwarded out that interface. The UDL Reporter is the IP address of the downstream interface on the receiving router. If there is more than one downstream router, this field shows which downstream router forwarded the IGMP host report to the upstream router over the ground-based network. This report is forwarded over the unidirectional link so that all downstream routers know which groups have already have been requested by other downstream routers, so that additional IGMP host reports are suppressed.
On the downstream router, this command (the Interface field) shows which local interface an IGMP host report (from a directly connected host for a specific group) was received on. The UDL Reporter is the IP address of the router that had forwarded the IGMP host report to the upstream router over the ground-based network. The UDL Interfaces column shows the interface on which IP multicast packets are being received.
Examples
The following is sample output of the show ip igmp udlr command on an upstream router:
upstream-rtr# show ip igmp udlrIGMP UDLR Status, UDL Interfaces: Serial0Group Address Interface UDL Reporter Reporter Expires224.2.127.254 Serial0 10.0.0.2 00:02:12224.0.1.40 Serial0 10.0.0.2 00:02:11225.7.7.7 Serial0 10.0.0.2 00:02:15The following is sample output of the show ip igmp udlr command on a downstream router:
downstream-rtr# show ip igmp udlrIGMP UDLR Status, UDL Interfaces: Serial0Group Address Interface UDL Reporter Reporter Expires224.2.127.254 Serial0 10.0.0.2 00:02:49224.0.1.40 Serial0 10.0.0.2 00:02:48225.7.7.7 Serial0 10.0.0.2 00:02:52Table 122 describes the significant fields in the first display.
tunnel udlr receive-only
To configure a unidirectional, generic routing encapsulation (GRE) tunnel to act as a back channel that can receive messages, when another interface is configured for unidirectional link routing (UDLR) to send messages, use the tunnel udlr receive-only interface configuration command. To remove the tunnel, use the no form of this command.
tunnel udlr receive-only type number
no tunnel udlr receive-only type number
Syntax Description
Defaults
No UDLR tunnel is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to configure a router that has a unidirectional interface with send-only capabilities. One example of when you might configure this command is if you have traffic traveling via a satellite.
The type and number arguments must match the send-only interface type and number specified by the interface command.
You must configure the tunnel udlr send-only command at the opposite end of the tunnel.
If you have a large number of receivers, you should configure UDLR by an alternative means: IGMP UDLR. See the ip igmp unidirectional-link command.
Examples
In the following example, Router A (the upstream router) is configured with OSPF and PIM. Serial interface 0 has send-only capability. Therefore, the UDLR tunnel is configured as receive only, and points to Serial 0.
Router A
ip multicast-routing!! Serial0 has send-only capability!interface serial 0encapsulation hdlcip address 10.1.0.1 255.255.0.0ip pim sparse-dense-mode!! Configure tunnel as receive-only UDLR tunnel.!interface tunnel 0tunnel source ethernet 0tunnel destination <downstream-router>tunnel udlr receive-only serial 0!! Configure OSPF.!router ospf <pid>network 10.0.0.0 0.255.255.255 area 0Router B (the downstream router) is configured with OSPF and PIM. Serial interface 1 has receive-only capability. Therefore, the UDLR tunnel is configured as send-only, and points to Serial 1.
Router B
ip multicast-routing!! Serial1 has receive-only capability!interface serial 1encapsulation hdlcip address 10.1.0.2 255.255.0.0ip pim sparse-dense-mode!! Configure tunnel as send-only UDLR tunnel.!interface tunnel 0tunnel source ethernet 0tunnel destination <upstream-router>tunnel udlr send-only serial 1!! Configure OSPF.!router ospf <pid>network 10.0.0.0 0.255.255.255 area 0Related Commands
tunnel udlr send-only
To configure a unidirectional, generic routing encapsulation (GRE) tunnel to act as a back channel that can send messages, when another interface is configured for unidirectional link routing (UDLR) to receive messages, use the tunnel udlr send-only interface configuration command. To remove the tunnel, use the no form of this command.
tunnel udlr send-only type number
no tunnel udlr send-only type number
Syntax Description
Defaults
No UDLR tunnel is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to configure a router that has a unidirectional interface with receive-only capabilities. The UDLR tunnel will act as a back channel. One example of when you might configure this command is if you have traffic traveling via a satellite.
The type and number arguments must match the receive-only interface type and number specified by the interface command.
You must configure the tunnel udlr receive-only command at the opposite end of the tunnel.
Examples
In the following example, Router A (the upstream router) is configured with OSPF and PIM. Serial interface 0 has send-only capability. Therefore, the UDLR tunnel is configured as receive only, and points to Serial 0.
Router A
ip multicast-routing!! Serial0 has send-only capability!interface serial 0encapsulation hdlcip address 10.1.0.1 255.255.0.0ip pim sparse-dense-mode!! Configure tunnel as receive-only UDLR tunnel.!interface tunnel 0tunnel source ethernet 0tunnel destination <downstream-router>tunnel udlr receive-only serial 0Router B (the downstream router) is configured with OSPF and PIM. Serial interface 1 has receive-only capability. Therefore, the UDLR tunnel is configured as send-only, and points to Serial 1.
Router B
ip multicast-routing!! Serial1 has receive-only capability!interface serial 1encapsulation hdlcip address 10.1.0.2 255.255.0.0ip pim sparse-dense-mode!! Configure tunnel as send-only UDLR tunnel.!interface tunnel 0tunnel source ethernet 0tunnel destination <upstream-router>tunnel udlr send-only serial 1Related Commands