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ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Prerequisites for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Restrictions for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Information About ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Benefits of ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Greater Service Resilience When Links Fail
Link Integrity Protocol Control Messages
Variable Bandwidth Class Support
Load Balancing with ASR1K Frame Relay-Multilink (MLFR-FRF.16)
How to Enable ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Configuring a Multilink Frame Relay Bundle
Configuring a Multilink Frame Relay Bundle Link
Monitoring and Maintaining ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Configuration Examples for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Example: Configuring Multilink Frame Relay
Example: Configuring Variable Bandwidth Class Support
Feature Information for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
ASR1K Frame Relay-Multilink (MLFR-FRF.16)
First Published: July 25, 2011Last Updated: July 25, 2011The ASR1K Frame Relay-Multilink (MLFR-FRF.16)Multilink-Frame Relay (MLFR-FRF.16) feature is based on the Frame Relay Forum Multilink Frame Relay UNI/NNI Implementation Agreement (FRF.16.1) on the Aggregation Service Routers. This feature provides a cost-effective way to increase bandwidth for particular applications by enabling multiple serial links to be aggregated into a single bundle of bandwidth. Multilink Frame Relay (MFR) is supported on User-Network Interfaces (UNI) in Frame Relay networks.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for ASR1K Frame Relay-Multilink (MLFR-FRF.16)" section.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Prerequisites for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Restrictions for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Information About ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Benefits of ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Flexible Pool of Bandwidth
By combining multiple physical interfaces into a bundle, you can design a Frame Relay interface that has more bandwidth than is available from any single physical interface. For example, many new network applications require more bandwidth than is available on a T1 line. One option is to invest in a T3 line; however, T3 lines can be expensive and are not available in some locations. Multilink Frame Relay provides a cost-effective solution to this problem by allowing multiple T1 lines to be aggregated into a single bundle of bandwidth.
Greater Service Resilience When Links Fail
Greater service resilience is provided when multiple physical interfaces are provisioned as a single bundle. When a link fails, the bundle continues to support the Frame Relay service by transmitting across the remaining bundle links.
Scalability
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Link Integrity Protocol Control Messages
For link management, each end of a bundle link follows the MFR Link Integrity Protocol and exchanges link-control messages with its peer (the other end of the bundle link). For a bundle link to be brought up, each end of the link must complete an exchange of ADD_LINK and ADD_LINK_ACK messages. To maintain the link, both ends periodically initiate the exchange of HELLO and HELLO_ACK messages. This exchange of hello messages and acknowledgments serves as a keepalive mechanism for the link. If a router is sending hello messages but not receiving acknowledgments, it will resend the hello message up to a configured maximum number of times. If the router exhausts the maximum number of retries, the bundle link line protocol is considered down (nonoperational).
The bundle link interface's line protocol status is considered up (operational) when the peer device acknowledges that it will use the same link for the bundle. The line protocol remains up when the peer device acknowledges the hello messages from the local router.
The bundle interface's line protocol status is considered up when the Frame Relay data link layer at the local router and peer device is synchronized using the Local Management Interface (LMI), when the LMI is enabled. The bundle line protocol remains up as long as the LMI keepalives are successful.
Variable Bandwidth Class Support
Multilink-Frame Relay (MLFR-FRF.16) variable bandwidth class support allows you to specify the criterion used to activate or deactivate a Frame Relay bundle.
Class A (Single Link)
The Frame Relay bundle is provisioned when one or more bundle links indicate by issuing a BL_ACTIVATE message that operational bandwidth is available. When this occurs, the bundle emulates a physical link by issuing a PH_ACTIVATE message to the data link layer.
When the operational bandwidth of a bundle link fails to meet operational requirements (for instance, if it is in rollback mode), the bundle link issues a BL_DEACTIVATE message. When all bundle links are down in a class A bundle, a PH_DEACTIVATE message is sent to the data link layer, indicating that the Frame Relay bundle cannot accept frames.
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Class B (All Links)
The Frame Relay bundle is provisioned when all bundle links indicate by issuing a BL_ACTIVATE message that operational bandwidth is available. When this occurs, the bundle emulates a physical link by issuing a PH_ACTIVATE message to the data link layer.
When the operational bandwidth of a bundle link fails to meet operational requirements (for instance, if it is in loopback mode), the bundle link issues a BL_DEACTIVATE message. When any bundle link is down in a class B bundle, a PH_DEACTIVATE message is sent to the data link layer, indicating that the Frame Relay bundle cannot accept frames.
Class C (Threshold)
The Frame Relay bundle is provisioned when the minimum number of links in the configured bundle issue a BL_ACTIVATE message. When this occurs, the bundle emulates a physical link by issuing a PH_ACTIVATE message to the data link layer.
When the number of bundle links that are issuing a BL_ACTIVATE message falls below the configured threshold value, a PH_DEACTIVATE message is sent to the data link layer, indicating that the Frame Relay bundle cannot accept frames.
Load Balancing with ASR1K Frame Relay-Multilink (MLFR-FRF.16)
MFR provides load balancing across the bundle links within a bundle. If a bundle link chosen for transmission happens to be busy transmitting a long packet, the load-balancing mechanism can try another link, thus solving the problems seen when delay-sensitive packets have to wait.
How to Enable ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Configuring a Multilink Frame Relay Bundle
Perform this task to configure the bundle for multilink Frame Relay.
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DETAILED STEPS
Configuring a Multilink Frame Relay Bundle Link
Tip
Perform this task to configure a bundle link interface for multilink Frame Relay.
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DETAILED STEPS
Monitoring and Maintaining ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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DETAILED STEPS
Examples
The following is sample output from the show frame-relay multilink command. Because a particular bundle or bundle link is not specified, information for all bundles and bundle links is displayed.
Router# show frame-relay multilinkBundle: MFR1, State = down, class = A, fragmentation disabledBID = router1Bundle links:Serial3/1, HW state = Administratively down, link state = Down, LID = second-linkSerial3/2, HW state = up, link state = Add_sent, LID = first-linkBundle: MFR1, State = down, class = B, fragmentation disabledBID = router1Bundle links:Serial3/0, HW state = Administratively down, link state = Down, LID = third-linkSerial3/1, HW state = Administratively down, link state = Down, LID = second-linkSerial3/2, HW state = up, link state = Add_sent, LID = first-linkThe following is sample output from the show frame-relay multilink command when a Frame Relay bundle is configured as bandwidth class C (threshold):
Router# show frame-relay multilinkBundle: MFR2, State = down, class = C (threshold 100), fragmentation disabledBID = router2Bundle links:Serial3/1, HW state = Administratively down, link state = Down, LID = cisco2Serial3/0, HW state = Administratively down, link state = Down, LID = cisco1The following is sample output from the show frame-relay multilink command when the Serial number keyword and argument pair is specified. It displays information about the specified bundle link.
Router# show frame-relay multilink Serial 3/2Bundle links:Serial3/2, HW state = up, link state = Add_sent, LID = first-linkBundle interface = MFR1, BID = router1The following is sample output from the show frame-relay multilink command when the Serial number keyword and argument pair and the detailed option is specified. Detailed information about the specified bundle links is displayed.
Router# show frame-relay multilink Serial 3/2 detailBundle links:Serial3/2, HW state = up, link state = Add_sent, LID = first-linkBundle interface = MFR1, BID = router1Cause code = none, Ack timer = 6, Hello timer = 9,Max retry count = 3, Current count = 0,Peer LID = , RTT = 0 msStatistics:Add_link sent = 110, Add_link rcv'd = 0,Add_link ack sent = 0, Add_link ack rcv'd = 0,Add_link rej sent = 0, Add_link rej rcv'd = 0,Remove_link sent = 0, Remove_link rcv'd = 0,Remove_link_ack sent = 0, Remove_link_ack rcv'd = 0,Hello sent = 0, Hello rcv'd = 0,Hello_ack sent = 0, Hello_ack rcv'd = 0,outgoing pak dropped = 0, incoming pak dropped = 0Configuration Examples for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
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Example: Configuring Multilink Frame Relay
The following example shows the configuration of bundle "MFR1." Serial interfaces 3/0 and 3/2 are configured as bundle links:
interface MFR1no ip addressframe-relay intf-type dceframe-relay multilink bid router1!interface MFR1.1 point-to-pointip address 10.0.0.1 255.255.255.0frame-relay interface-dlci 100interface Serial3/0encapsulation frame-relay MFR1frame-relay multilink lid first-linkframe-relay multilink hello 9frame-relay multilink retry 3frame-relay multilink ack 4interface Serial3/2encapsulation frame-relay MFR1frame-relay multilink lid first-linkframe-relay multilink hello 8frame-relay multilink ack 3frame-relay multilink retry 2Example: Configuring Variable Bandwidth Class Support
The following example configures the Frame Relay bundle "MFR2" to use the class B (all links) criterion to be activated or deactivated:
interface MFR2frame-relay multilink bandwidth-class bframe-relay intf-type dceframe-relay multilink bid router2exitinterface MFR2.2 point-to-pointip address 10.1.1.10 255.255.255.0frame-relay interface-dlci 145endAdditional References
Related Documents
Standards
MIBs
None
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
Technical Assistance
Feature Information for ASR1K Frame Relay-Multilink (MLFR-FRF.16)
Table 2 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 2 Feature Information for Multilink-Frame Relay (MLFR-FRF.16)
ASR1K Frame Relay - Multilink (MLFR-FRF.16)
Cisco IOS XE Release 3.4S
The ASR1K Frame Relay-Multilink (MLFR-FRF.16) feature is based on the Frame Relay Forum Multilink Frame Relay UNI/NNI Implementation Agreement (FRF.16.1) on the Aggregation Service Routers.
The following sections provide information about this feature:
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The following commands were introduced or modified: debug frame-relay multilink, encapsulation frame-relay mfr, frame-relay multilink ack, frame-relay multilink bandwidth-class, frame-relay multilink bid, frame-relay multilink hello, frame-relay multilink lid, frame-relay multilink retry, interface mfr, show frame-relay multilink.
Glossary
BID—bundle identification. The BID is the name used to identify the bundle. The BID can be assigned, or the default can be used.
BL_ACTIVATE—A message that controls the addition of a bundle link to a Frame Relay bundle.
BL_DEACTIVATE—A message that controls the removal a bundle link from a Frame Relay bundle.
bundle—A logical grouping of one or more physical interfaces using the formats and procedures of multilink Frame Relay. A bundle emulates a physical interface to the Frame Relay data link layer. The bundle is also referred to as the MFR interface.
bundle link—An individual physical interface that is a member of a bundle.
DLCI—data-link connection identifier. A value that identifies a permanent virtual circuit (PVC) in a Frame Relay network.
HELLO message—A message that notifies a peer endpoint that the local endpoint is in the operational state (up).
HELLO_ACK—A message that notifies a peer endpoint that a hello message has been received.
LID—link identification. The LID is the name used to identify a bundle link. The LID can be assigned, or the default can be used.
LMI—Local Management Interface. A set of enhancements to the basic Frame Relay specification. LMI includes support for a keepalive mechanism, which verifies that data is flowing; a multicast mechanism, which provides the network server with its local DLCI and the multicast DLCI; global addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a status mechanism, which provides an ongoing status report on the DLCIs known to the switch.
NNI—Network-to-Network Interface. The interface between two Frame Relay devices that are both located in a private network or both located in a public network.
PH_ACTIVATE—A message that indicates that the Frame Relay bundle is up.
PH_DEACTIVATE—A message that indicates that the Frame Relay bundle is down.
UNI—User-Network Interface. The interface between a Frame Relay device in a public network and a Frame Relay device in a private network.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© 2011 Cisco Systems, Inc. All rights reserved.
