Frame Relay Fast Restart
Feature History
Release
Modification
12.0(18)ST
This feature was introduced on the Cisco 10000 series routers.
12.0(19)ST1
This feature was introduced on the Cisco 7500 series routers.
12.0(22)S
This feature was integrated into Cisco IOS Release 12.0(22)S.
This document describes the Frame Relay Fast Restart feature in Cisco IOS Release 12.0(22)S. It
includes the following sections:
•
Feature Overview, page 1
•
Supported Platforms, page 3
•
Supported Standards, MIBs, and RFCs, page 3
•
Configuration Tasks, page 4
•
Configuration Examples, page 5
•
Command Reference, page 6
Feature Overview
The Frame Relay Fast Restart feature increases network availability by reducing recovery time from
Route Processor (RP) failures on Cisco 7500 series and Cisco 10000 series routers in Frame Relay
networks. This feature reduces recovery time by accelerating the transition from primary RP to standby
RP after a hardware or software failure.
When a switchover from primary RP to standby RP occurs on a switch with Frame Relay line cards, the
switch must implement an initialization procedure to bring permanent virtual circuits (PVCs) back up
and to reestablish dynamic mappings. While this procedure is under way, the Frame Relay interface is
unavailable for traffic forwarding. Before the introduction of this feature, the initialization procedure
took from 30 to 90 seconds to complete on each Frame Relay interface. The Frame Relay Fast Restart
feature reduces interface restart time to 10 to 15 seconds.
The Frame Relay Fast Restart feature uses the methods described in the following sections to reduce
interface restart time:
•
Accelerating the LMI Cycle
•
Accelerating Inverse ARP
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Feature Overview
Accelerating the LMI Cycle
To address the possibility that the line protocol is down upon switchover to the standby RP, the Frame
Relay Fast Restart feature introduces an accelerated Local Management Interface (LMI) cycle. The
accelerated LMI cycle is designed to bring the line protocol up quickly, in turn making PVCs available
sooner.
Before the introduction of Frame Relay Fast Restart, LMI polling cycles occurred every 10 seconds, and
on the sixth cycle a full LMI status request was sent. This pattern resulted in the sending of a full LMI
status request every 60 seconds. With the accelerated LMI cycle, a full status request is sent to the switch
immediately after switchover to the standby RP. The next polling cycle begins within 1 second following
receipt of the full status from the switch rather than waiting the default 10 seconds. A full status request
is also sent at the last polling cycle. The accelerated LMI cycle ends after a fixed number of polling
cycles, which can be configured to meet the requirements of the switch.
The accelerated LMI cycle causes the line protocol to come up and PVCs to be reported active in 1 or 2
seconds instead of the 30 to 40 seconds that it would have taken before the introduction of this feature.
Note
It may take an additional 10 seconds before the remote router sees that the PVCs are up.
Note
The accelerated DTE LMI cycle is nonstandard and may cause problems for some DCE LMI
implementations. When the DTE device is directly connected to a Cisco DCE device that is
terminating PVCs, the DCE device must be running a Cisco IOS software release based on Cisco IOS
Release 12.0(18)ST, 12.0(17.6)S, 12.1(9.1), or 12.2(2.2) or later.
Accelerating Inverse ARP
Inverse Address Resolution Protocol (ARP) requests, where applicable, will be sent out as soon as a PVC
becomes active. Before the introduction of the Frame Relay Fast Restart feature, when an Inverse ARP
request was unsuccessful, the request was resent every 60 seconds. This new feature accelerates the
Inverse ARP timer so that if a request comes back unsuccessful, a second request is sent in 10 seconds.
Subsequent requests are sent every 60 seconds.
Benefits
The Frame Relay Fast Restart feature increases network availability by reducing the recovery time from
hardware and software failures on Cisco routers in Frame Relay networks. This feature enables PVCs to
be available for use within 10 to 15 seconds of switchover to a standby Route Processor; in contrast,
before the introduction of this feature, it could take from 30 to 90 seconds.
Restrictions
The Frame Relay Fast Restart feature supports only the following interfaces and connections:
•
Serial interfaces
•
DTE LMI type
•
PVCs (switched and terminated)
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Supported Platforms
Related Documents
•
Cisco IOS Wide-Area Networking Configuration Guide, Release 12.0
•
Cisco IOS Wide-Area Networking Command Reference, Release 12.0
Supported Platforms
•
Cisco 7500 series
•
Cisco 10000 series
Determining Platform Support Through Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated
information regarding platform support for this feature, access Feature Navigator. Feature Navigator
dynamically updates the list of supported platforms as new platform support is added for the feature.
Feature Navigator is a web-based tool that enables you to quickly determine which Cisco IOS software
images support a specific set of features and which features are supported in a specific Cisco IOS image.
To access Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your
account information, send a blank e-mail to [email protected]. An automatic check will verify
that your e-mail address is registered with Cisco.com. If the check is successful, account details with a
new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com
by following the directions at http://www.cisco.com/register.
Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases
occur. For the most current information, go to the Feature Navigator home page at the following URL:
http://www.cisco.com/go/fn
Supported Standards, MIBs, and RFCs
Standards
No new standards are supported by this feature.
MIBs
No new MIBs are supported by this feature.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules,
go to the Cisco MIB website on Cisco.com at
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
No new RFCs are supported by this feature.
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Configuration Tasks
Configuration Tasks
See the following sections for configuration tasks for the Frame Relay Fast Restart feature. Each task in
the list is identified as either required or optional.
•
Enabling Frame Relay Fast Restart on the Router (required)
•
Enabling Frame Relay Fast Restart on an Interface (optional)
•
Changing the Number of Accelerated LMI Polling Cycles (optional)
•
Configuration Examples (optional)
Enabling Frame Relay Fast Restart on the Router
To enable Frame Relay Fast Restart on the router, use the following command in global configuration
mode:
Command
Purpose
Router(config)# frame-relay fast-restart
Enables Frame Relay fast restart on the router and sets the default
number of accelerated polling cycles to be completed to 4 cycles.
Enabling Frame Relay Fast Restart on an Interface
Entering the frame-relay fast-restart command in global configuration mode will enable Frame Relay
Fast Restart on all interfaces. Frame Relay Fast Restart can be disabled on individual interfaces using
the no frame-relay fast-restart command in interface configuration mode.
To reenable Frame Relay Fast Restart if it was disabled on an interface using the no frame-relay
fast-restart command, use the following commands in interface configuration mode:
Command
Purpose
Step 1
Router(config-if)# encapsulation frame-relay
Enables Frame Relay encapsulation.
Step 2
Router(config-if)# frame-relay fast-restart [poll
number-of-cycles]
Enables Frame Relay Fast Restart on the interface.
This command can also be used to configure the
number of accelerated LMI polling cycles for the
interface. The default is 4 cycles. The range is from
1 to 10.
Note
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In order for Frame Relay Fast Restart to work
on an interface, it must be enabled on the
router using the frame-relay fast-restart
command in global configuration mode.
Frame Relay Fast Restart
Configuration Examples
Changing the Number of Accelerated LMI Polling Cycles
To change the number of accelerated LMI polling cycles that will be completed for an interface, use the
following commands in interface configuration mode:
Command
Purpose
Step 1
Router(config-if)# encapsulation frame-relay
Enables Frame Relay encapsulation.
Step 2
Router(config-if)# frame-relay fast-restart [poll
number-of-cycles]
Enables Frame Relay Fast Restart on the interface.
This command can also be used to configure the
number of accelerated LMI polling cycles for the
interface. The default is 4 cycles. The range is from
1 to 10.
Note
In order for Frame Relay Fast Restart to work
on an interface, it must be enabled on the
router using the frame-relay fast-restart
command in global configuration mode.
Verifying Frame Relay Fast Restart
To verify the configuration of Frame Relay Fast Restart, use the show running-config command in
EXEC mode:
Router# show running-config
Building configuration...
Current configuration : 17801 bytes
!
version 12.0
.
.
.
ip cef distributed
no ip domain-lookup
ip host host1
frame-relay fast-restart <!--indicates frame-relay fast-restart is enabled-->
!
!
Configuration Examples
This section provides the following configuration example:
•
Frame Relay Fast Restart Example
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Command Reference
Frame Relay Fast Restart Example
In the following example, Frame Relay Fast Restart is enabled on the router, and the accelerated LMI
poll timer is set to complete 3 polling cycles:
frame-relay fast-restart
interface Serial0/0/0/1:1
ip address 131.180.60.5 255.255.255.0
encapsulation frame-relay
frame-relay fast-restart poll 3
frame-relay map ip 131.180.60.10 100
frame-relay intf-type dte
Command Reference
This section documents new commands. All other commands used with this feature are documented in
the Cisco IOS Release 12.2 command reference publications.
•
frame-relay fast-restart (global)
•
frame-relay fast-restart (interface)
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frame-relay fast-restart (global)
frame-relay fast-restart (global)
To enable Frame Relay Fast Restart functionality on the router, use the frame-relay fast-restart
command in global configuration mode. To disable Frame Relay Fast Restart functionality, use the no
form of this command.
frame-relay fast-restart
no frame-relay fast-restart
Syntax Description
This command has no arguments or keywords.
Defaults
Frame Relay Fast Restart is not enabled by default.
Frame Relay Fast Restart will complete 4 accelerated LMI cycles by default.
Command Modes
Global configuration
Command History
Release
Modification
12.0(18)ST
This command was introduced on Cisco 10000 series routers.
12.0(19)ST1
This command was introduced on Cisco 7500 series routers.
12.0(22)S
This command was integrated into Cisco IOS Release 12.0(22)S.
Usage Guidelines
Frame Relay fast restart reduces the time needed for permanent virtual circuits (PVCs) to become active
and for dynamic mappings to become established after a primary-to-standby Route Processor
switchover.
Frame Relay Fast Restart can be disabled on individual interfaces by using the no frame-relay
fast-restart command in interface configuration mode.
To configure the number of accelerated Local Management Interface (LMI) polling cycles to be
completed when Frame Relay Fast Restart is enabled, use the frame-relay fast-restart command in
interface configuration mode. The default number of polling cycles is 4.
Note
The frame-relay fast-restart command enables an accelerated DTE Local Management Interface
(LMI) cycle that is nonstandard and may cause problems for some DCE LMI implementations. When
the DTE device is directly connected to a Cisco DCE device that is terminating PVCs, the DCE
device must be running a Cisco IOS software release based on Cisco IOS Release 12.0(19)ST,
12.0(17.6)S, 12.1(9.1), or 12.2(2.2) or later.
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frame-relay fast-restart (global)
Examples
In the following example, Frame Relay Fast Restart is enabled, and the accelerated LMI poll timer is set
to complete a minimum of 3 cycles:
frame-relay fast-restart
interface Serial0/0/0/1:1
ip address 131.180.60.5 255.255.255.0
encapsulation frame-relay
frame-relay fast-restart poll 3
frame-relay map ip 131.180.60.10 100
frame-relay intf-type dte
The following example shows Frame Relay Fast Restart enabled on the router but disabled on serial
interface 0/0/0/1:1:
frame-relay fast-restart
interface Serial0/0/0/1:1
no frame-relay fast-restart
Related Commands
Command
Description
frame-relay
Enables Frame Relay Fast Restart functionality on the interface and
fast-restart (interface) configures the number of accelerated LMI polling cycles.
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frame-relay fast-restart (interface)
frame-relay fast-restart (interface)
To enable Frame Relay Fast Restart functionality on the interface and to configure the number of
accelerated Local Management Interface (LMI) polling cycles, use the frame-relay fast-restart
command in interface configuration mode. To disable Frame Relay Fast Restart functionality on the
interface, use the no form of this command.
frame-relay fast-restart [poll number-of-cycles]
no frame-relay fast-restart
Syntax Description
poll number-of-cycles
Defaults
4 cycles
Command Modes
Interface configuration
Command History
Release
Usage Guidelines
(Optional) Number of accelerated LMI polling cycles. The range is from
1 to 10.
Modification
12.0(18)ST
This command was introduced on Cisco 10000 series routers.
12.0(19)ST1
This command was introduced on Cisco 7500 series routers.
12.0(22)S
This command was integrated into Cisco IOS Release 12.0(22)S.
Frame Relay Fast Restart reduces the time needed for permanent virtual circuits (PVCs) to become
active and for dynamic mappings to become established after a primary-to-standby Route Processor
switchover.
Frame Relay Fast Restart will not work unless it has been enabled on the router by using the frame-relay
fast-restart command in global configuration mode.
Frame Relay Fast Restart uses an accelerated LMI cycle in which a full status request is sent to the switch
immediately after switchover to the standby Route Processor. The next polling cycle begins within 1
second following receipt of the full status from the switch. A full status request is also sent at the last
polling cycle. You can use the frame-relay fast-restart command in interface configuration mode to
configure the number of polling cycles that will be completed.
To reset the number of accelerated LMI polling cycles to the default setting, use the frame-relay
fast-restart command in interface configuration mode.
Examples
The following example configures LMI to complete 6 accelerated polling cycles:
interface Serial0/0/0/1:1
ip address 131.180.60.5 255.255.255.0
encapsulation frame-relay
frame-relay fast-restart poll 6
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frame-relay fast-restart (interface)
Related Commands
Command
Description
frame-relay fast-restart (global)
Enables Frame Relay Fast Restart functionality on the router.
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Glossary
Glossary
DTE—data terminal equipment. Device at the user end of a user-network interface that serves as a data
source, destination, or both. DTE connects to a data network through a data communications equipment
(DCE) device (for example, a modem) and typically uses clocking signals generated by the DCE. DTE
includes such devices as computers, protocol translators, and multiplexers.
Inverse ARP—Inverse Address Resolution Protocol. Method of building dynamic routes in a network.
Allows an access server to discover the network address of a device associated with a virtual circuit.
LMI—Local Management Interface. 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 data-link connection identifier (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.
PVC—permanent virtual circuit. Virtual circuit that is permanently established. PVCs save bandwidth
associated with circuit establishment and teardown in situations where certain virtual circuits must exist
all the time.
RP—Route Processor. Processor module that contains the CPU, system software, and most of the
memory components that are used in the router.
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Glossary
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