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Table Of Contents
UDLR Tunnel ARP and IGMP Proxy
Supported Standards, MIBs, and RFCs
Integrated UDLR Tunnel, IGMP UDLR, and IGMP Proxy Example
tunnel udlr address-resolution
UDLR Tunnel ARP and IGMP Proxy
This feature module describes the UDLR Tunnel ARP and IGMP Proxy enhancements to the Unidirectional Link Routing (UDLR) feature and includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
Most protocols in the Internet assume that links are bidirectional. In particular, routing protocols used by directly connected routers no longer behave properly in the presence of a unidirectional link, such as a satellite link. The Unidirectional Link Routing feature, introduced in Cisco IOS Release 12.0(3)T, enables a router to emulate the behavior of a bidirectional link for operation of IP over unidirectional links.
The unidirectional link routing (UDLR) enhancements introduced in this feature module include enhancements to the existing UDLR tunnel mechanism and the addition of the Internet Group Management Protocol (IGMP) proxy mechanism.
UDLR Tunnel Enhancements
In Cisco IOS Release 12.1(5)T, the following enhancements were made to the existing UDLR tunnel mechanism of the Unidirectional Link Routing feature:
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IGMP Proxy
When UDLR was introduced in Cisco IOS Release 12.0(3)T, it was delivered with two mechanisms for bidirectional link emulation: UDLR tunneling and IGMP UDLR. As of Cisco IOS Release 12.1(5)T, the UDLR capability is now delivered with three complementary mechanisms for bidirectional link emulation: UDLR tunneling, IGMP UDLR, and IGMP Proxy. Each mechanism may be used independently or in conjunction with either or both of the other mechanisms.
The IGMP Proxy mechanism was added to the Unidirectional Link Routing feature to permit hosts that are not directly connected to a downstream router to be able to join a multicast group sourced from an upstream network. Figure 1 illustrates this mechanism.
Figure 1 IGMP Mroute Proxy Mechanism
In the scenario in Figure 1, the following sequence of events occur:
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In an enterprise network, for example, it is desirable to receive IP multicast traffic via satellite and to be able to forward the traffic throughout the network. With IGMP UDLR alone, this scenario is not possible because receiving hosts must be directly connected to the downstream router. The IGMP Proxy mechanism overcomes this limitation by creating an IGMP report for (*, G) entries in the multicast forwarding table. To make this scenario work, the network administrator must configure PIM sparse mode (PIM-SM) in the network, make the UDL downstream router the rendezvous point (RP) for a select set of addresses, and configure mroute proxy on interfaces leading to PIM enabled networks with potential members. When the UDL downstream router has a (*, G) forwarding entry for an mroute proxy interface, an IGMP report for the group is created and sent to a loopback interface (IGMP Proxy interface). The loopback interface then uses the same mechanism as IGMP UDLR to forward reports upstream.
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Benefits
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Related Documents
For related information on the Unidirectional Link Routing feature, refer to the following documents:
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Supported Platforms
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Supported Standards, MIBs, and RFCs
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
To obtain lists of MIBs supported by platform and Cisco IOS release and to download MIB modules, go to the Cisco web site on Cisco Connection Online (CCO) at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
No new or modified RFCs are supported by this feature.
Configuration Tasks
See the following sections for configuration tasks for the IGMP Proxy feature. Each task in the list is identified as either optional or required:
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Configuring IGMP Proxy
To configure IGMP Proxy, use the following commands in interface configuration mode:
Verifying IGMP Proxy
To verify that IGMP Proxy is configured properly, use the show ip igmp command.
Configuration Examples
This section provides the following configuration examples:
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IGMP Proxy Example
In the following example, Router C sends a PIM-SM Join message to Router B for multicast group G. Router B will request an IGMP report for group G to Router A. Router A will then forward group G multicast traffic over the unidirectional link. Figure 2 illustrates this example.
Figure 2 IGMP Mroute Proxy Topology
Router A
interface ethernet 0ip address 10.1.1.1 255.255.255.0ip pim dense-mode!interface ethernet 1ip address 10.2.1.1 255.255.255.0ip pim dense-modeip igmp unidirectional link!interface ethernet 2ip address 10.3.1.1 255.255.255.0Router B
ip pim rp-address 10.5.1.1 5access-list 5 permit 239.0.0.0 0.255.255.255.255!interface loopback 0ip address 10.7.1.1 255.255.255.0ip pim dense-modeip igmp helper-address udl ethernet 0ip igmp proxy-service!interface ethernet 0ip address 10.2.1.2 255.255.255.0ip pim dense-modeip igmp unidirectional link!interface ethernet 1ip address 10.5.1.1 255.255.255.0ip pim sparse-modeip igmp mroute-proxy loopback 0!interface ethernet 2ip address 10.6.1.1 255.255.255.0Router C
ip pim rp-address 10.5.1.1 5access-list 5 permit 239.0.0.0 0.255.255.255!interface ethernet 0ip address 10.8.1.1 255.255.255.0ip pim sparse-mode!interface ethernet 1ip address 10.9.1.1 255.255.255.0ip pim sparse-modeIntegrated UDLR Tunnel, IGMP UDLR, and IGMP Proxy Example
The following example shows how to configure UDLR tunnels, IGMP UDLR, and IGMP Proxy on both the upstream and downstream routers sharing a unidirectional link.
Upstream
ip multicast-routing!!!interface Tunnel0ip address 9.1.89.97 255.255.255.252no ip directed-broadcasttunnel source 9.1.89.97tunnel mode gre multipointtunnel key 5tunnel udlr receive-only Ethernet2/3!interface Ethernet2/0no ip addressshutdown!! user networkinterface Ethernet2/1ip address 9.1.89.1 255.255.255.240no ip directed-broadcastip pim dense-modeip cgmpfair-queue 64 256 128no cdp enableip rsvp bandwidth 1000 100!interface Ethernet2/2ip address 9.1.95.1 255.255.255.240no ip directed-broadcast!! physical send-only interfaceinterface Ethernet2/3ip address 9.1.92.100 255.255.255.240no ip directed-broadcastip pim dense-modeip nhrp network-id 5ip nhrp server-onlyip igmp unidirectional-linkfair-queue 64 256 31ip rsvp bandwidth 1000 100!router ospf 1network 9.1.92.96 0.0.0.15 area 1!ip classlessip route 9.1.90.0 255.255.255.0 9.1.92.99!Downstream
ip multicast-routing!!!interface Loopback0ip address 9.1.90.161 255.255.255.252ip pim sparse-modeip igmp helper-address udl Ethernet2/3ip igmp proxy-service!interface Tunnel0ip address 9.1.90.97 255.255.255.252ip access-group 120 outno ip directed-broadcastno ip mroute-cachetunnel source 9.1.90.97tunnel destination 9.1.89.97tunnel key 5tunnel udlr send-only Ethernet2/3tunnel udlr address-resolution!interface Ethernet2/0no ip addressno ip directed-broadcastshutdownno cdp enable!! user networkinterface Ethernet2/1ip address 9.1.90.1 255.255.255.240no ip directed-broadcastip pim sparse-modeip igmp mroute-proxy Loopback0no cdp enable!! Backchannelinterface Ethernet2/2ip address 9.1.95.3 255.255.255.240no ip directed-broadcastno cdp enable!! physical receive-only interfaceinterface Ethernet2/3ip address 9.1.92.99 255.255.255.240no ip directed-broadcastip pim sparse-modeip igmp unidirectional-linkno keepaliveno cdp enable!router ospf 1network 9.1.90.0 0.0.0.255 area 1network 9.1.92.96 0.0.0.15 area 1!ip classlessip route 0.0.0.0 0.0.0.0 9.1.95.1! set rpf to be the physical receive-only interfaceip mroute 0.0.0.0 0.0.0.0 9.1.92.96ip pim rp-address 9.1.90.1!! permit ospf, ping and rsvp, deny othersaccess-list 120 permit icmp any anyaccess-list 120 permit 46 any anyaccess-list 120 permit ospf any anyCommand Reference
This section documents the following new commands. All other commands used with the UDLR feature are documented in the Cisco IOS Release command reference publications.
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ip igmp mroute-proxy
To enable Internet Group Management Protocol (IGMP) report forwarding of proxied (*, G) mroute entries, use the ip igmp proxy-service interface configuration command. To disable this service, use the no form of this command.
ip igmp mroute-proxy type number
no ip igmp mroute-proxy type number
Syntax Description
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
When used with the ip igmp proxy-service interface command, this command enables forwarding of Internet Group Management Protocol (IGMP) reports to a proxy service interface for all (*, G) forwarding entries for this interface in the multicast forwarding table.
Examples
The following example shows how to configure the ip igmp mroute-proxy command on Ethernet 1 to request that IGMP reports be sent to Loopback 0 for all groups in the mroute table that are forwarded to Ethernet 1. This example also shows how to configure the ip igmp proxy-service command on Loopback 0 to enable the forwarding of IGMP reports out the interface for all groups on interfaces registered through the ip igmp mroute-proxy command.
interface loopback 0ip address 10.7.1.1 255.255.255.0ip pim dense-modeip igmp helper-address udl ethernet 0ip igmp proxy-service!interface ethernet 0ip address 10.2.1.1 255.255.255.0ip pim dense-modeip igmp unidirectional link!interface ethernet 1ip address 10.1.1.1 255.255.255.0ip pim sparse-modeip igmp mroute-proxy loopback 0Related Commands
Enables the mroute proxy service.
ip igmp unidirectional-link
Configures an interface to be unidirectional and enables it for IGMP UDLR.
ip igmp proxy-service
To enable the mroute proxy service, use the ip igmp mroute-proxy interface configuration command. To disable forwarding, use the no form of this command.
ip igmp proxy-service
no ip igmp proxy-service
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
Based on the IGMP query interval, the router periodically checks the mroute table for (*, G) forwarding entries that match interfaces configured with the ip igmp mroute-proxy command. Where there is a match, one IGMP report is created and received on this interface. This command was intended to be used with the ip igmp helper-address udl command, in which case the IGMP report would be forwarded to an upstream router.
Examples
The following example shows how to configure the ip igmp mroute-proxy command on Ethernet 1 to request that IGMP reports be sent to Loopback 0 for all groups in the mroute table that are forwarded to Ethernet 1. This example also shows how to configure the ip igmp proxy-service command on Loopback 0 to enable the forwarding of IGMP reports out the interface for all groups on interfaces registered through the ip igmp mroute-proxy command.
interface loopback 0ip address 10.7.1.1 255.255.255.0ip pim dense-modeip igmp helper-address udl ethernet 0ip igmp proxy-service!interface ethernet 0ip address 10.2.1.1 255.255.255.0ip pim dense-modeip igmp unidirectional link!interface ethernet 1ip address 10.1.1.1 255.255.255.0ip pim sparse-modeip igmp mroute-proxy loopback 0Related Commands
tunnel udlr address-resolution
To enable the forwarding of Address Resolution Protocol (ARP) and Next Hop Resolution Protocol (NHRP) over a unidirectional link, use the tunnel udlr address-resolution interface configuration command. To disable forwarding, use the no form of this command.
tunnel udlr address-resolution
no tunnel udlr address-resolution
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
This command is configured on the send-only tunnel interface of a downstream router.
Examples
The following example shows how to configure the tunnel udlr address-resolution command on an interface to enable ARP and NHRP over a send-only tunnel. An ARP address resolution request received from the upstream router on the unidirectional link (Ethernet 0) will be replied to over the send-only tunnel of the receiver. Likewise, an ARP request may be sent by the downstream router over the send-only tunnel, and the response will be received over the unidirectional link.
interface tunnel 0tunnel udlr send-only ethernet 0tunnel udlr address-resolutionRelated Commands
tunnel udlr send-only
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.
