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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.
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
Syntax Description
udl type number Interface type and number of unidirectional interface.
Defaults
No forwarding occurs.
Command Modes
Interface configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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 0 description Forward IGMP reports from this interface to UDL querier ip address 14.0.0.2 255.0.0.0 ip pim sparse-dense-mode ip igmp helper-address udl serial 0
Related Commands
Configures an interface to be unidirectional and enables it for IGMP UDLR.
Command
Description
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-linkSyntax Description
This command has no arguments or keywords.
Defaults
No unidirectional link routing occurs.
Command Modes
Interface configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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 0 description Unidirectional to downlink-rtr ip address 10.0.0.1 255.0.0.0 ip pim sparse-dense-mode ip igmp unidirectional-link no keepalive
Related Commands
Configures IGMP helpering as required for IGMP UDLR. Changes the distance given to the default RPF interface when configuring IGMP unidirectional link routing. Displays UDLR information for directly connected multicast groups on interfaces that have a unidirectional link helper address configured. Configures a unidirectional, GRE tunnel to act as a back channel that can receive messages, when another interface is configured for UDLR to send messages. Configures a unidirectional, GRE tunnel to act as a back channel that can send messages, when another interface is configured for UDLR to receive messages.
Command
Description
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
Syntax Description
distance Distance given to the default RPF interface. The default value is 15.
Defaults
The distance default value is 15.
Command Modes
Global configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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:
Examples
The following example configures a distance of 20:
ip multicast default-rpf-distance 20
Related Commands
Configures an interface to be unidirectional and enables it for IGMP UDLR.
Command
Description
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
12.0(3)T This command was introduced.
Release
Modification
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 udlr IGMP UDLR Status, UDL Interfaces: Serial0 Group Address Interface UDL Reporter Reporter Expires 224.2.127.254 Serial0 10.0.0.2 00:02:12 224.0.1.40 Serial0 10.0.0.2 00:02:11 225.7.7.7 Serial0 10.0.0.2 00:02:15
The following is sample output of the show ip igmp udlr command on a downstream router:
downstream-rtr# show ip igmp udlr IGMP UDLR Status, UDL Interfaces: Serial0 Group Address Interface UDL Reporter Reporter Expires 224.2.127.254 Serial0 10.0.0.2 00:02:49 224.0.1.40 Serial0 10.0.0.2 00:02:48 225.7.7.7 Serial0 10.0.0.2 00:02:52
Table 118 describes the significant fields in the first display.
| Field | Description |
|---|---|
Group Address | All groups helpered by the reporter on the interface. |
Interface | Interface type and number to which the group is connected. |
UDL Reporter | IP address of the router on the UDL network that is IGMP helpering for the group. |
Reporter Expires | How soon the reporter will become inactive, in hours:minutes:seconds. This can occur under the following conditions:
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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
Syntax Description
type number Interface type and number. Make this type and number match the unidirectional send-only interface type and number specified by the interface command. Thus, when packets are received over the tunnel, the upper layer protocols will believe the packets are received over the unidirectional send-only interface.
Defaults
No UDLR tunnel is configured.
Command Modes
Interface configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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 0 encapsulation hdlc ip address 10.1.0.1 255.255.0.0 ip pim sparse-dense-mode ! ! Configure tunnel as receive-only UDLR tunnel. ! interface tunnel 0 tunnel source ethernet 0 tunnel destination <downstream-router> tunnel udlr receive-only serial 0 ! ! Configure OSPF. ! router ospf <pid> network 10.0.0.0 0.255.255.255 area 0
Router 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 1
encapsulation hdlc
ip address 10.1.0.2 255.255.0.0
ip pim sparse-dense-mode
!
! Configure tunnel as send-only UDLR tunnel.
!
interface tunnel 0
tunnel source ethernet 0
tunnel destination <upstream-router>
tunnel udlr send-only serial 1
!
! Configure OSPF.
!
router ospf <pid>
network 10.0.0.0 0.255.255.255 area 0
Related Commands
interface Defines the IP addresses of the server, configures an interface type, and enters interface configuration mode. interface tunnel Configures a tunnel interface. Configures an interface to be unidirectional and enables it for IGMP UDLR. Configures a unidirectional, GRE tunnel to act as a back channel that can send messages, when another interface is configured for UDLR to receive messages.
Command
Description
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
Syntax Description
type number Interface type and number. Make this type and number match the unidirectional receive-only interface type and number specified by the interface command. Thus, when packets are sent by upper layer protocols over the interface, they will be redirected and sent over this GRE tunnel.
Defaults
No UDLR tunnel is configured.
Command Modes
Interface configuration
Command History
12.0(3)T This command was introduced.
Release
Modification
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 0 encapsulation hdlc ip address 10.1.0.1 255.255.0.0 ip pim sparse-dense-mode ! ! Configure tunnel as receive-only UDLR tunnel. ! interface tunnel 0 tunnel source ethernet 0 tunnel destination <downstream-router> tunnel udlr receive-only serial 0
Router 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 1
encapsulation hdlc
ip address 10.1.0.2 255.255.0.0
ip pim sparse-dense-mode
!
! Configure tunnel as send-only UDLR tunnel.
!
interface tunnel 0
tunnel source ethernet 0
tunnel destination <upstream-router>
tunnel udlr send-only serial 1
Related Commands
interface Defines the IP addresses of the server, configures an interface type, and enters interface configuration mode. interface tunnel Configures a tunnel interface. Configures an interface to be unidirectional and enables it for IGMP UDLR. Configures a unidirectional, GRE tunnel to act as a back channel that can receive messages, when another interface is configured for UDLR to send messages.
Command
Description
Posted: Thu Jul 27 13:30:35 PDT 2000
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