Table Of Contents
General Description of the ATM T1/E1 IMA Feature Set
Supported Standards, MIBs, and RFCs
Verifying the ATM Interface Configuration
Verifying IMA Group Configuration
Monitoring and Maintaining ATM Inverse Multiplexing
ima differential-delay-maximum
Configuring Multiport T1/E1 ATM Network Modules with Inverse Multiplexing over ATM on Cisco 2600 and 3600 Series Routers
This document describes the Cisco IOS Inverse Multiplexing for ATM (IMA) features available with the introduction of Multiport T1/E1 ATM network modules with IMA for the Cisco 2600 and 3600 series routers. It includes the following sections:
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Supported Standards, MIBs, and RFCs
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Feature Overview
Inverse multiplexing provides the capability to transmit and receive a single high-speed data stream over multiple slower-speed physical links. In inverse multiplexing over ATM, the originating stream of ATM cells is divided so that complete ATM cells are transmitted in round-robin order across the set of ATM links.
Asynchronous Transfer Mode (ATM) T1 and E1 IMA network modules provide four or eight T1 or E1 ports with inverse multiplexing capability. These modules allow wide-area networking (WAN) uplinks at speeds ranging from 1.536 Mbps to 12.288 Mbps for T1, and from 1.92 Mbps to 15.36 Mbps for E1. See the "Bandwidth Considerations" section.
Cisco's scalable ATM IMA solution means that you can deploy just the bandwidth you need by using multiple E1 or T1 connections instead of a more expensive E3, T3, or OC-3 to bridge between LANs and ATM WAN applications. Enterprises and branch offices can aggregate traffic from multiple low-bandwidth digital physical transmission media, such as T1 pipes, to transmit voice and data at high-bandwidth connection speeds. For example, illustrates a scenario where an organization must transport a mission-critical application among headquarters and branch offices at 6 Mbps.
Figure 1
LAN-to-WAN Application Connectivity with T1 and IMA
IMA Protocol Overview
In the transmit direction, IMA takes cells from the ATM layer and sends them in a round-robin order over the individual links that make up a logical link group called an IMA group (links can also be assigned as individuals rather than as group members). The IMA group performance is approximately the sum of the links, although some overhead is required for ATM control cells. At the receiving end, the cells are recombined to form the original cell stream and are passed up to the ATM layer.
Filler cells are used to ensure a steady stream on the receiving side. IMA control protocol (ICP) cells control the operation of the inverse multiplexing function. Using a frame length of 128, one out of every 128 cells on each link is an ICP cell. The inverse multiplexing operation is transparent to the ATM layer protocols; therefore, the ATM layer can operate normally as if only a single physical interface were being used.
illustrates inverse multiplexing and demultiplexing with four bundled links, providing 6.144 Mbps of bandwidth for T1s and 7.68 Mbps of bandwidth for E1 for packet traffic. The transmit side, where cells are distributed across the links, is referred to as Tx, and the receive side, where cells are recombined, is called Rx.
Figure 2 Inverse Multiplexing and Demultiplexing
General Description of the ATM T1/E1 IMA Feature Set
ATM networks were designed to handle the demanding performance needs of voice, video, and data at broadband speeds of 34 Mbps and above. However, the high cost and spotty availability of long-distance broadband links limits broadband ATM WANs, preventing many organizations from taking advantage of ATM's power. In response to these issues, the ATM Forum defined lower-speed ATM interface options for T1 and E1. However, this was not a complete solution because a single T1 or E1 link often does not provide enough bandwidth to support either traffic among different router and switch locations or heavy end-user demand.
For this reason, many organizations find themselves caught between the bandwidth limitations of a narrowband T1 or E1 line and the much higher costs of moving to broadband links. In response to this dilemma, the ATM Forum, with Cisco as an active member, defined Inverse Multiplexing for ATM (IMA). Using Cisco 2600 and 3600 series routers to provide ATM access gives branch offices and enterprises an affordable LAN-to-ATM interface.
ATM IMA T1/E1 support on the Cisco 2600 and 3600 series routers includes the following features:
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Benefits
The following benefits are offered by the ATM T1/E1 IMA features for the Cisco 2600 and 3600 series routers:
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Restrictions
This section describes general restrictions and ATM aspects that the ATM IMA feature does not support as well as bandwidth considerations.
General Limitations
The following restrictions apply to the ATM IMA feature on the Cisco 2600 and 3600 series:
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Bandwidth Considerations
When planning IMA groups and payload bandwidth requirements, consider the overhead required for ATM cell headers, service-layer encapsulation such as RFC 1483, AAL5 encapsulation, and ICP cells. and show approximate values for T1 and E1 IMA groups, respectively with a frame length of 128, estimating ATM overhead at about 10 percent. The effective payload bandwidth varies based on packet size because the packets must be divided into an integer number of ATM cells leaving the last cell padded with filler bytes.
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Related Documents
The following Cisco IOS Release 12.0 documents provide information about ATM configuration:
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For information about the physical characteristics of the ATM T1/E1 IMA network modules, or for instructions on how to install the network or modem modules, either see the Cisco 2600 or 3600 series Network Module Hardware Installation Guide that came with your ATM T1/E1 IMA network module or view the up-to-date information on CCO.
Supported Platforms
The ATM IMA feature is supported on the following modular access routers:
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Supported Standards, MIBs, and RFCs
This feature supports the following MIBs:
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For descriptions of supported MIBs and how to use MIBs, see Cisco's MIB website on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
This feature supports the following RFCs:
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Prerequisites
Before you can configure a Cisco 2600 or 3600 series router to provide ATM IMA T1/E1 service, you must perform the following tasks:
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Configuration Tasks
This section describes the configuration tasks required in order to set up ATM IMA groups. You can also configure ATM links individually, but this feature description only includes those individual configuration steps that may pertain to ATM IMA groups.
Perform the following configuration tasks in order to enable ATM inverse multiplexing:
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Configuring the ATM Interface
Repeat the steps below to configure each ATM interface for ATM IMA operation.
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Enter global configuration mode.
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Enter interface configuration mode and specify the location of the interface.
The slot value indicates the router slot position of the installed network module. Depending on the router, enter a slot value from 0 to 3.
The port value indicates the T1 or E1 link that you are configuring. Enter a value from 0 to 3 or from 0 to 7, depending on whether the network module has four ports or eight ports. Cisco IOS creates the interfaces automatically when a module is installed.
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loop-timed}The clock source command sets the clock source for a link.
line specifies that the link uses the recovered clock from the link and is the default setting. Generally, this setting is most reliable.
internal specifies that the DS1 link uses the internal clock.
loop-timed specifies that the T1 or E1 interface takes the clock from the Rx (line) and uses it for Tx. If the ATM interface is part of an IMA group, you can use the loop-timed keyword to specify that the clock source is the same as the IMA group clock source.
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Router(config-if)# cablelength long {gain26 | gain36}
{-15db | -22.5db | -7.5db | 0db}or
cablelength short {133 | 266 | 399 | 533 | 655}(T1 interfaces only) To set a cable length longer than 655 feet for a T1 link, use the cablelength long command. The keywords are as follows:
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To set a cable length 655 feet or shorter for a T1 link, use the short command. There is no default for cablelength short. The keywords are as follows:
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If you do not set the cable length, the system defaults to a setting of cablelength long gain26 0db.
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Instead of configuring protocol parameters on the physical interface, you can set up the parameters on the IMA group virtual interface.
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The no atm oversubscribe command1 enables the ATM bandwidth manager, which keeps track of bandwidth used by virtual circuits on a per-interface basis. This is useful because many services, such as ABR and VBR-RT, require guaranteed bandwidth. When you specify the no form of the command, a check determines whether the ATM link is already oversubscribed. If it is, the command is rejected. Otherwise, the total bandwidth available on the link is recorded and all future connection setup requests are monitored to ensure that the link is not oversubscribed.
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Normally, the default setting for this command is sufficient. Helping to ensure reliability, scrambling randomizes the ATM cell payload frames to avoid continuous non-variable bit patterns and improve the efficiency of ATM's cell delineation algorithms. By default, payload scrambling is on for E1 links and off for T1 links.
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(E1 interfaces only) This command specifies the impedance (amount of wire resistance and reactivity to current) for the E1 link. Impedance levels are maintained to avoid data corruption over long-distance links. The impedance is determined by the dongle-type cable that you plug in to the IMA module. Set this command to match that cable.
Specify 120-ohm to match the unbalanced twisted-pair 120-ohm interface. This is the default.
75-ohm is for a balanced BNC 750-ohm interface.
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remote](For testing only) This command is useful for testing because it loops all packets from the ATM interface back to the interface and directs the packets to the network.
The default line setting places the interface into external loopback mode at the line.
remote keeps the local end of the connection in remote loopback mode.
local places the interface into local loopback mode.
payload places the interface into external loopback at the payload level.
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Router(config-if)# fdl {att | ansi | all | none}(Optional, T1 only) This command sets the Facility Data Link (FDL) exchange standard for the CSU controllers. The FDL is a 4-Kpbs channel used with the Extended SuperFrame (ESF) framing format to provide out-of-band messaging for error-checking on a T1 link.
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You should generally leave this setting at the default, ansi, which follows the ANSI T1.403 standard for extended superframe facilities data link exchange support. Changing it allows improved management in some cases but can cause problems if your setting is not compatible with that of your service provider.
att selects the AT&T TR54016 standard for extended superframe facilities data link exchange support.
all enables both of the above standards.
none means that there is no standard suported for the FDL exchange standard.
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This command specifies that the link is included in an IMA group. Enter an IMA group number from 0 to 3. You can specify up to four groups for each IMA network module. IMA groups usually span multiple ports on a module.
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This command ensures that the link is active at the IMA level. If shut down, the link is added to the group but put in an inhibited state.
1 This command was introduced in Cisco IOS Release 12.0(3)T. For more information, see the online feature description, ATM OC-3 Network Module for the Cisco 3600 Series Routers, on CCO at http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t3/oc3_fm.htm.
Verifying the ATM Interface Configuration
Follow the steps below to verify the configuration of ATM interfaces.
Step 1
router# show interface atm0/1ATM0/1 is up, line protocol is upHardware is ATM T1Internet address is 21.1.1.2/8MTU 4470 bytes, sub MTU 4470, BW 1500 Kbit, DLY 20000 usec,reliability 0/255, txload 1/255, rxload 1/255Encapsulation ATM, loopback not setKeepalive not supportedEncapsulation(s): AAL5256 maximum active VCs, 3 current VCCsVC idle disconnect time: 300 secondsLast input never, output never, output hang neverLast clearing of "show interface" counters neverQueueing strategy: fifoOutput queue 0/40, 0 drops; input queue 0/75, 0 drops5 minute input rate 0 bits/sec, 0 packets/sec5 minute output rate 0 bits/sec, 0 packets/sec0 packets input, 0 bytes, 0 no bufferReceived 0 broadcasts, 0 runts, 0 giants, 0 throttles0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort0 packets output, 0 bytes, 0 underruns0 output errors, 0 collisions, 3 interface resets0 output buffer failures, 0 output buffers swapped outStep 2
router# show controller atm0/2Interface ATM0/2 is administratively downHardware is ATM T1LANE client MAC address is 0050.0f0c.1482hwidb=0x617BEE9C, ds=0x617D498Cslot 0, unit 2, subunit 2rs8234 base 0x3C000000, slave base 0x3C000000rs8234 ds 0x617D498CSBDs - avail 2048, guaranteed 2, unguaranteed 2046, starved 0Seg VCC table 3C00B800, Shadow Seg VCC Table 617EF76C, VCD Table 61805798Schedule table 3C016800, Shadow Schedule table 618087C4, Size 63DRSM VCC Table 3C02ED80, Shadow RSM VCC Table 6180C994VPI Index Table 3C02C300, VCI Index Table 3C02E980Bucket2 Table 3C01E500, Shadow Bucket2 Table 6180A0E4MCR Limit Table 3C01E900, Shadow MCR Table 617D2160ABR template 3C01EB00, Shadow template 614DEEACRM Cell RS Queue 3C02C980Queue TXQ Addr Pos StQ Addr Pos0 UBR CHN0 3C028B00 0 03118540 01 UBR CHN1 3C028F00 0 03118D40 02 UBR CHN2 3C029300 0 03119540 03 UBR CHN3 3C029700 0 03119D40 04 VBR/ABR CHN0 3C029B00 0 0311A540 05 VBR/ABR CHN1 3C029F00 0 0311AD40 06 VBR/ABR CHN2 3C02A300 0 0311B540 07 VBR/ABR CHN3 3C02A700 0 0311BD40 08 VBR-RT CHN0 3C02AB00 0 0311C540 09 VBR-RT CHN1 3C02AF00 0 0311CD40 010 VBR-RT CHN2 3C02B300 0 0311D540 011 VBR-RT CHN3 3C02B700 0 0311DD40 012 SIG 3C02BB00 0 0311E540 013 VPD 3C02BF00 0 0311ED40 0Queue FBQ Addr Pos RSQ Addr Pos0 OAM 3C0EED80 255 0311F600 01 UBR CHN0 3C0EFD80 0 03120600 02 UBR CHN1 3C0F0D80 0 03121600 03 UBR CHN2 3C0F1D80 0 03122600 04 UBR CHN3 3C0F2D80 0 03123600 05 VBR/ABR CHN0 3C0F3D80 0 03124600 06 VBR/ABR CHN1 3C0F4D80 0 03125600 07 VBR/ABR CHN2 3C0F5D80 0 03126600 08 VBR/ABR CHN3 3C0F6D80 0 03127600 09 VBR-RT CHN0 3C0F7D80 0 03128600 010 VBR-RT CHN1 3C0F8D80 0 03129600 011 VBR-RT CHN2 3C0F9D80 0 0312A600 012 VBR-RT CHN3 3C0FAD80 0 0312B600 013 SIG 3C0FBD80 255 0312C600 0SAR Scheduling channels: -1 -1 -1 -1 -1 -1 -1 -1Part of IMA group 3Link 2 IMA Info:group index is 1Tx link id is 2, Tx link state is unusableNoGivenReasonRx link id is 99, Rx link state is unusableFaultRx link failure status is fault,0 tx failures, 3 rx failuresLink 2 Framer Info:framing is ESF, line code is B8ZS, fdl is ANSIcable-length is long, Rcv gain is 26db and Tx gain is 0db,clock src is line, payload-scrambling is disabled, no loopbackline status is 0x1064; or Tx RAI, Rx LOF, Rx LOS, Rx LCD.port is active, link is unavailable0 idle rx, 0 correctable hec rx, 0 uncorrectable hec rx0 cells rx, 599708004 cells tx, 0 rx fifo overrun.Link (2):DS1 MIB DATA:Data in current interval (518 seconds elapsed):0 Line Code Violations, 0 Path Code Violations0 Slip Secs, 518 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 519 Unavail SecsTotal Data (last 24 hours)0 Line Code Violations, 0 Path Code Violations,0 Slip Secs, 86400 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 86400 Unavail SecsSAR counter totals across all links and groups:0 cells output, 0 cells stripped0 cells input, 0 cells discarded, 0 AAL5 frames discarded0 pci bus err, 0 dma fifo full err, 0 rsm parity err0 rsm syn err, 0 rsm/seg q full err, 0 rsm overflow err0 hs q full err, 0 no free buff q err, 0 seg underflow err0 host seg stat q full errConfiguring IMA Groups
As shown in the previous section, the ima-group command configures links on an ATM interface as IMA group members. When IMA groups have been set up in this way, you can configure settings for each group.
Verifying IMA Group Configuration
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Router# show ima interface ATM2/IMA2Interface ATM2/IMA2 is upGroup index is 2Ne state is operational, failure status is noFailureactive links bitmap 0x30IMA Group Current Configuration:Tx/Rx configured links bitmap 0x30/0x30Tx/Rx minimum required links 1/1Maximum allowed diff delay is 25ms, Tx frame length 128Ne Tx clock mode CTC, configured timing reference link ATM2/4Test pattern procedure is disabledIMA Group Current Counters (time elapsed 12 seconds):3 Ne Failures, 3 Fe Failures, 4 Unavail SecsIMA Group Total Counters (last 0 15 minute intervals):0 Ne Failures, 0 Fe Failures, 0 Unavail SecsIMA link Information:Link Physical Status NearEnd Rx Status Test Status---- --------------- ----------------- -----------ATM2/4 up active disabledATM2/5 up active disabledrouter# show ima interface ATM2/IMA2 detailInterface ATM2/IMA2 is upGroup index is 2Ne state is operational, failure status is noFailureactive links bitmap 0x30IMA Group Current Configuration:Tx/Rx configured links bitmap 0x30/0x30Tx/Rx minimum required links 1/1Maximum allowed diff delay is 25ms, Tx frame length 128Ne Tx clock mode CTC, configured timing reference link ATM2/4Test pattern procedure is disabledDetailed group Information:Tx/Rx Ima_id 0x22/0x40, symmetry symmetricOperationNumber of Tx/Rx configured links 2/2Number of Tx/Rx active links 2/2Fe Tx clock mode ctc, Rx frame length 128Tx/Rx timing reference link 4/4Maximum observed diff delay 0ms, least delayed link 5Running seconds 32GTSM last changed 10:14:41 UTC Wed Jun 16 1999IMA Group Current Counters (time elapsed 33 seconds):3 Ne Failures, 3 Fe Failures, 4 Unavail SecsIMA Group Total Counters (last 0 15 minute intervals):0 Ne Failures, 0 Fe Failures, 0 Unavail SecsDetailed IMA link Information:Interface ATM2/4 is upifIndex 13, Group Index 2, Row Status is activeTx/Rx Lid 4/4, relative delay 0msNe Tx/Rx state active/activeFe Tx/Rx state active/activeNe Rx failure status is noFailureFe Rx failure status is noFailureRx test pattern 0x41, test procedure disabledIMA Link Current Counters (time elapsed 35 seconds):1 Ima Violations, 0 Oif Anomalies1 Ne Severely Err Secs, 2 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs2 Ne Tx Unusable Secs, 2 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 2 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresIMA Link Total Counters (last 0 15 minute intervals):0 Ima Violations, 0 Oif Anomalies0 Ne Severely Err Secs, 0 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs0 Ne Tx Unusable Secs, 0 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 0 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresInterface ATM2/5 is upifIndex 14, Group Index 2, Row Status is activeTx/Rx Lid 5/5, relative delay 0msNe Tx/Rx state active/activeFe Tx/Rx state active/activeNe Rx failure status is noFailureFe Rx failure status is noFailureRx test pattern 0x41, test procedure disabledIMA Link Current Counters (time elapsed 46 seconds):1 Ima Violations, 0 Oif Anomalies1 Ne Severely Err Secs, 2 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs2 Ne Tx Unusable Secs, 2 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 2 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresIMA Link Total Counters (last 0 15 minute intervals):0 Ima Violations, 0 Oif Anomalies0 Ne Severely Err Secs, 0 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs0 Ne Tx Unusable Secs, 0 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 0 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresStep 2
router# show controller atm0/ima3Interface ATM0/IMA3 is upHardware is ATM IMALANE client MAC address is 0050.0f0c.148bhwidb=0x61C2E990, ds=0x617D498Cslot 0, unit 3, subunit 3rs8234 base 0x3C000000, slave base 0x3C000000rs8234 ds 0x617D498CSBDs - avail 2048, guaranteed 3, unguaranteed 2045, starved 0Seg VCC table 3C00B800, Shadow Seg VCC Table 617EF76C, VCD Table 61805798Schedule table 3C016800, Shadow Schedule table 618087C4, Size 63DRSM VCC Table 3C02ED80, Shadow RSM VCC Table 6180C994VPI Index Table 3C02C300, VCI Index Table 3C02E980Bucket2 Table 3C01E500, Shadow Bucket2 Table 6180A0E4MCR Limit Table 3C01E900, Shadow MCR Table 617D2160ABR template 3C01EB00, Shadow template 614DEEACRM Cell RS Queue 3C02C980Queue TXQ Addr Pos StQ Addr Pos0 UBR CHN0 3C028B00 0 03118540 01 UBR CHN1 3C028F00 0 03118D40 02 UBR CHN2 3C029300 0 03119540 03 UBR CHN3 3C029700 0 03119D40 04 VBR/ABR CHN0 3C029B00 0 0311A540 05 VBR/ABR CHN1 3C029F00 0 0311AD40 06 VBR/ABR CHN2 3C02A300 0 0311B540 07 VBR/ABR CHN3 3C02A700 0 0311BD40 08 VBR-RT CHN0 3C02AB00 0 0311C540 09 VBR-RT CHN1 3C02AF00 0 0311CD40 010 VBR-RT CHN2 3C02B300 0 0311D540 011 VBR-RT CHN3 3C02B700 0 0311DD40 012 SIG 3C02BB00 0 0311E540 013 VPD 3C02BF00 0 0311ED40 0Queue FBQ Addr Pos RSQ Addr Pos0 OAM 3C0EED80 255 0311F600 01 UBR CHN0 3C0EFD80 0 03120600 02 UBR CHN1 3C0F0D80 0 03121600 03 UBR CHN2 3C0F1D80 0 03122600 04 UBR CHN3 3C0F2D80 0 03123600 05 VBR/ABR CHN0 3C0F3D80 0 03124600 06 VBR/ABR CHN1 3C0F4D80 0 03125600 07 VBR/ABR CHN2 3C0F5D80 0 03126600 08 VBR/ABR CHN3 3C0F6D80 0 03127600 09 VBR-RT CHN0 3C0F7D80 0 03128600 010 VBR-RT CHN1 3C0F8D80 255 03129600 011 VBR-RT CHN2 3C0F9D80 0 0312A600 012 VBR-RT CHN3 3C0FAD80 0 0312B600 013 SIG 3C0FBD80 255 0312C600 0SAR Scheduling channels: -1 -1 -1 -1 -1 -1 -1 -1ATM channel number is 1link members are 0x7, active links are 0x0Group status is blockedNe, 3 links configured,Group Info: Configured links bitmap 0x7, Active links bitmap 0x0,Tx/Rx IMA_id 0x3/0x63,NE Group status is startUp,frame length 0x80, Max Diff Delay 0,1 min links, clock mode ctc, symmetry symmetricOperation, trl 0,Group Failure status is startUpNe.Test pattern procedure is disabledSAR counter totals across all links and groups:0 cells output, 0 cells stripped0 cells input, 0 cells discarded, 0 AAL5 frames discarded0 pci bus err, 0 dma fifo full err, 0 rsm parity err0 rsm syn err, 0 rsm/seg q full err, 0 rsm overflow err0 hs q full err, 0 no free buff q err, 0 seg underflow err0 host seg stat q full errStep 3
VCD / Peak Avg/Min BurstInterface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts0/1 1 0 50 PVC SNAP UBR 1000 INAC0/IMA3 2 0 5 PVC SAAL UBR 4000 UP0/IMA3 3 0 16 PVC ILMI UBR 4000 UP0/IMA3 first 1 13 PVC MUX VBR 640 320 80 UP0/IMA3 4 0 34 SVC SNAP VBR-RT 768 768 UPTroubleshooting Tips
To troubleshoot the ATM and IMA group configuration, enter the ping EXEC (user) or privileged EXEC command that checks host reachability and network connectivity. This command can confirm basic network connectivity on AppleTalk, ISO CLNS, IP, Novell, Apollo, VINES, DECnet, or XNS networks.
For IP, the ping command sends ICMP (Internet Control Message Protocol) Echo messages. If a station receives an ICMP Echo message, it sends an ICMP Echo Reply message back to the source.
The extended command mode of the ping command permits you to specify the supported IP header options, so that the router can perform a more extensive range of test options. To enter ping extended command mode, enter yes at the extended commands prompt of the ping command.
For detailed information on using the ping and extended ping commands, see the Cisco IOS Release 12.0 Configuration Fundamentals Command Reference.
If a ping command fails, check the following possible reasons for the connectivity problem:
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Tips
Use the ping command when the network is functioning properly to see how the command works under normal conditions and so that you can compare the results when troubleshooting.
If a communication session is closing when it should not be, an end-to-end connection problem can be the cause. The debug ip packet command is useful for analyzing the messages traveling between the local and remote hosts. IP debugging information includes packets received, generated, and forwarded. Because the debug ip packet command generates a significant amount of output, use it only when traffic on the IP network is low, so other activity on the system is not adversely affected.
Monitoring and Maintaining ATM Inverse Multiplexing
Configuration Examples
This section shows two sample configurations: one for a router that is set up for E1 ATM IMA and one for T1 ATM IMA.
E1 IMA Configuration
The following configuration example shows setup of ATM interfaces, IMA groups, PVCs, and SVCs for E1 IMA.
version 12.0service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname IMARouter!logging buffered 4096 debugging!ip subnet-zerono ip domain-lookupip host 10.11.16.2ip host 10.11.16.3ip host 10.11.55.192ip host 10.11.55.193ip host 10.11.55.195ip host 10.11.55.196!!!!interface Ethernet0/0ip address 10.17.12.100 255.255.255.192no ip directed-broadcast!ATM interface 1/0 includes a PVC, but the specified link is not included in an IMA group. In this example, impedance and scrambling are set at their default values for E1 links and must match the far-end setting. The broadcast setting on the PVC takes precedence (addresses are fictional).
interface ATM1/0ip address 10.1.1.26 255.255.255.1no ip directed-broadcastno atm oversubscribepvc 1/40protocol ip 10.10.10.10 broadcast!scrambling-payloadimpedance 120-ohmno fair-queue!The eight-port ATM IMA E1 network module is in slot 1, and the interface commands below specify three links as members of IMA group 0.
interface ATM1/1no ip addressno ip directed-broadcastno atm oversubscribeima-group 0scrambling-payloadimpedance 120-ohmno fair-queue!interface ATM1/2no ip addressno ip directed-broadcastno atm oversubscribeima-group 0scrambling-payloadimpedance 120-ohmno fair-queue!interface ATM1/3no ip addressno ip directed-broadcastno atm oversubscribeima-group 0scrambling-payloadimpedance 120-ohmno fair-queue!Four links are members of IMA group 1.
interface ATM1/4no ip addressno ip directed-broadcastno atm oversubscribeima-group 1scrambling-payloadimpedance 120-ohmno fair-queue!interface ATM1/5no ip addressno ip directed-broadcastno atm oversubscribeima-group 1scrambling-payloadimpedance 120-ohmno fair-queue!interface ATM1/6no ip addressno ip directed-broadcastno atm oversubscribeima-group 1scrambling-payloadimpedance 120-ohmno fair-queue!interface ATM1/7no ip addressno ip directed-broadcastno atm oversubscribeima-group 1scrambling-payloadimpedance 120-ohmno fair-queue!The following commands specify parameters for the two IMA groups. For each group, a PVC is created and assigned an IP address.
interface ATM1/IMA0ip address 10.18.16.123 255.255.255.192no ip directed-broadcastima clock-mode common port 2no atm oversubscribepvc 1/42protocol ip 10.10.10.10 broadcast!!interface ATM1/IMA1ip address 10.19.16.123 255.255.255.192no ip directed-broadcastno atm oversubscribeima active-links-minimum 3pvc 1/99protocol ip 10.10.10.10 broadcast!!ip classlessip route 0.0.0.0 0.0.0.0 10.18.16.193ip route 10.91.0.1 255.255.255.255 10.1.0.2no ip http server!!!line con 0exec-timeout 0 0history size 100transport input noneline aux 0line vty 0 4exec-timeout 0 0password labloginhistory size 100!endT1 IMA Configuration
The following configuration example shows setup of ATM interfaces, IMA groups, PVCs, and SVCs for T1 IMA.
version 12.0service timestamps debug uptimeservice timestamps log uptimeno service password-encryptionno service dhcp!hostname router!!!!!!ip subnet-zero!!!!!There are four links in IMA group 3. The no scrambling-payload command is actually unnecessary, because this is the default for T1 links. The T1 automatic B8ZS line encoding is normally sufficient for proper cell delineation, so no scrambling-payload is the usual setting for T1 links, The scrambling setting must match the far end.
interface ATM0/0no ip addressno ip directed-broadcastno atm ilmi-keepaliveima-group 3no scrambling-payloadno fair-queue!interface ATM0/1ip address 10.18.16.121 255.255.255.192no ip directed-broadcastno atm ilmi-keepalive!ima-group 3no scrambling-payloadno fair-queue!interface ATM0/2no ip addressno ip directed-broadcastno atm ilmi-keepaliveima-group 3no scrambling-payloadno fair-queue!interface ATM0/3no ip addressno ip directed-broadcastno atm ilmi-keepaliveima-group 3no scrambling-payloadno fair-queue!!IMA group 3 has PVCs that are set up for SVC management and signaling. Two SVCs and a communications PVC are also set up on the group interface.
interface ATM0/IMA3no ip addressno ip directed-broadcastno atm ilmi-keepalivepvc 0/16 ilmi!pvc 0/5 qsaal!!pvc first 1/43vbr-rt 640 320 80encapsulation aal5mux ip!!svc second nsap 47.0091810000000050E201B101.00107B09C6ED.FEabr 4000 3000!!svc nsap 47.0091810000000002F26D4901.444444444444.01!The IMA subcommands below specify that three links must be active in order for the group to be operational. The common clock source is the first link, ATM 0/1, and ATM 0/2 is the test link. The differential delay maximum is set to 50 milliseconds.
ima active-links-minimum 3ima clock-mode common 1ima differential-delay-maximum 50ima test link 2!interface Ethernet1/0no ip addressno ip directed-broadcastshutdown!interface Ethernet1/1no ip addressno ip directed-broadcastshutdown!ip classlessno ip http server!!!line con 0exec-timeout 0 0transport input noneline aux 0line vty 0 4login!!endCommand Reference
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
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In Cisco IOS Release 12.0(1)T or later, you can search and filter the output for show and more commands. This functionality is useful when you need to sort through large amounts of output, or if you want to exclude output that you do not need to see.
To use this functionality, enter a show or more command followed by the "pipe" character (|), one of the keywords begin, include, or exclude, and an expression that you want to search or filter on:
command | {begin | include | exclude} regular-expression
Following is an example of the show atm vc command in which you want the command output to begin with the first line where the expression "PeakRate" appears:
show atm vc | begin PeakRate
For more information on the search and filter functionality, refer to the Cisco IOS Release 12.0(1)T feature module titled CLI String Search.
cablelength long
To set a cable length longer than 655 feet for a DS1 link, enter the cablelength long interface configuration command on the interface for a T1 link. The no form of this command sets the cable length to the default values, cablelength long gain26 0db.
cablelength long {gain26 | gain36} {-15db | -22.5db | -7.5db | 0db}
no cablelength long
Syntax Description
Defaults
gain26 and 0db.
Command Mode
Interface configuration
Command History
Usage Guidelines
This command is supported on T1 long-haul links only. If you enter the cablelength long command on a DSX-1 (short haul) interface, the command is rejected.
The transmit attenuation value is best obtained by experimentation. If the signal received by the far-end equipment is too strong, reduce the transmit level by entering additional attenuation.
Example
On a Cisco 2600 or 3600 series router, the following example specifies a pulse gain of 36 and a decibel pulse rate of -7.5 decibels:
interface atm 0/2cablelength long gain36 -7.5dbRelated Command
cablelength short
To set a cable length of 655 feet or shorter for a DS1 link, enter the cablelength short interface configuration command. This command is supported on T1 interfaces only. The no form of this command deletes the cablelength short value and sets the default of cablelength long gain26 0db.
cablelength short {133 | 266 | 399 | 533 | 655}
no cablelength short
Syntax Description
Default
No default value or behavior
Command Mode
Interface configuration
Command History
Usage Guidelines
This command is supported on T1short-haul links only. If you enter the cablelength short command on a long-haul interface, the command is rejected.
Example
On a Cisco 2600 or 3600 series router, the following example specifies a cable length from 0 to 133 feet:
interface atm 0/2cablelength short 133Related Command
clock source
To configure the clock source of a DS1 link, enter the clock source interface configuration command. The no form of the command restores the default line setting.
clock source {line | internal | loop-timed}
no clock source
Syntax Description
Default
The default value is line.
Command Mode
Interface configuration
Command History
Usage Guidelines
This command sets clocking for individual T1/E1 links.
Make sure that you specify the clock source correctly for each link, even if you are planning to specify that a certain link will provide clocking for all the links in an IMA group. Because links may be taken in and out of service, requiring that the system select another link for common clocking, any link in an IMA group may provide the common clock.
If the ATM interface is part of an IMA group, you can use the loop-timed keyword to specify that the clock source is the same as the IMA group clock source.
Example
On a Cisco 2600 or 3600 series router, the following example specifies an internal clock source for the link:
interface atm 0/2clock source internalRelated Command
fdl
To set the Faciity Data Link (FDL) exchange standard for a T1 interface that uses Extended SuperFrame (ESF) framing format, enter the fdl interface configuration command. The no form of this command specifies that there is no ESF FDL.
fdl {att | ansi | all | none}
no fdl {att | ansi | all | none}
Syntax Description
Default
The default value is ansi.
Command Mode
Interface configuration
Command History
Usage Guidelines
This command is available for T1 links only and sets the standard that will be followed for FDL messaging through a 4-Kbps out-of-band channel that a service provider uses to check for errors on the facility. You must use the same FDL exchange standard as your service provider. If the setting is not correct, the link may fail to come up. You can have a different standard configured on each T1 interface.
Note
Example
On a Cisco 2600 or 3600 series router, the following example specifies both ANSI and AT&T standards for FDL exchange:
interface atm 0/2fdl allima active-links-minimum
To set the minimum number of links that must be operating in order for an ATM IMA group to remain in service, execute the IMA interface configuration command ima active-links-minimum. The no form of the command removes the current configuration and sets the value to the default.
ima active-links-minimum number
no ima active-links-minimum number
Syntax Description
Default
The default is one link.
Command Mode
Interface configuration
Command History
Usage Guidelines
The minimum number of links that should be active for continued group operation depends upon the applications you are using and the speeds they require. ATM frame size and the number of links in a group affect the overhead required by ATM.
When planning, you should assume that only the bandwidth supplied by the minimal number of links will be available. If you decrease the value set in this command, make sure that virtual circuits of a higher bandwidth than the minimum supported by the command are torn down as necessary.
Example
On a Cisco 2660 or 3600 series router, the following example specifies that two links in IMA group 2 must be operational in order for the group to remain in service:
interface atm 0/ima2ima active-links-minimum 2ima clock-mode
To set the transmit clock mode for an ATM IMA group, execute the IMA interface configuration command ima clock-mode. If all the links in the group share a clock source, use the common keyword. If all the links use different clock sources, use the independent clock source keyword. The no form of the command removes the current configuration.
ima clock-mode {common port | independent}
no ima clock-mode
Syntax Description
Default
The default value is common. If no port is specified, the system automatically chooses an active link to provide clocking.
Command Mode
Interface configuration
Command History
Usage Guidelines
This command controls the clock for the IMA group as a whole. When the independent keyword is set, the clock source ATM interface configuration command is used under each interface to determine clocking individually. When the common keyword is set, the clock source ATM interface configuration command for the common link determines clocking for all the links in the group.
Because the system automatically chooses a replacement for the common link when it fails, any link in an IMA group potentially can provide the recovered transmit clock. For this reason, even when the common keyword is set with a specific link stipulated by the port value, you should use the ATM interface configuration clock source command to make sure that the clock source is configured correctly on each interface in the IMA group.
Example
On a Cisco 2600 or 3600 series router, the following example specifies that the links in IMA group 2 use a common clock source on link 0:
interface atm0/ima2ima clock-mode common 0Related Commands
ima differential-delay-maximum
To specify the maximum allowed differential timing delay that can exist among the active links in an IMA group, enter the ima differential-delay-maximum IMA interface configuration command. If a link delay exceeds the specified maximum, the link is dropped; otherwise, the IMA feature adjusts for differences in delays so that all links in a group are aligned and carry ATM-layer traffic. The no form of the command restores the default setting.
ima differential-delay-maximum msec
no ima differential-delay-maximum msec
Syntax Description
Default
The default value is 25 ms.
Command Mode
Interface configuration
Command History
Usage Guidelines
This command helps control latency in ATM-layer traffic by setting a limit on how much latency the slowest link in the group is allowed to introduce (a slower link has a longer propagation delay—for example, due to a longer path through through the network or less accurate physical layer clocking—than other links). Setting a high value allows a slow link to continue operating as part of the group, although such a setting means there is added delay to links across the group. A low setting may result in less latency for traffic across the group than a high setting, but it can mean that the system takes a slow link out of operation, reducing total bandwidth.
When a link has been removed from service, it is automatically placed back in service when it meets the delay differential standard.
Example
On a Cisco 2600 or 3600 series router, the following example specifies that the links in IMA group 2 have a maximum differential delay of 50 ms:
interface atm0/ima2ima differential-delay-maximum 50Related Command
show ima interface atm
This command shows differential delay information about an IMA group.
ima-group
To define physical linkd as IMA group members, execute the ima-group configuration command for each group member. When you first perform the configuration or when you change the group number, the interface is automatically disabled, moved to the new group, and then enabled. The no form of the command removes the port from the group.
ima-group group-number
no ima-group group-number
Syntax Description
group-number
Enter an IMA group number from 0 to 3. IMA groups can span multiple ports on a network module but cannot span network modules.
Default
By default, physical links are not included in IMA groups.
Command Mode
Interface configuration
Command History
Example
On a Cisco 2600 or 3600 series router, the following example makes interface 1 on the ATM module in slot 0 a member of IMA group 2:
interface atm0/1ima-group 2Related Commands
ima test
To specify an interface and a test pattern, execute the ima test IMA configuration command. To verify link and group connectivity, the pattern is sent from the specified link and looped back from the receiving end across all links belonging to the group as defined at the remote end. This can help troubleshoot physical link connectivity or configuration problems at the remote end. The local end verifies that the pattern is returned on all links belonging to the group at the local end, and testing is continuous. An ICP cell in each frame identifies the pattern. The no form of the command stops the test.
ima test [link port] [pattern pattern-id]
no ima test [link port] [pattern pattern-id]
Syntax Description
Defaults
There is no default for the port value. The default value for pattern-id is 106 (0x6A).
Command Mode
Interface configuration
Command History
Command Usage
When a link is not transmitting or receiving a pattern correctly, the command reports the link number where the problem exists.
Example
On a Cisco 2600 or 3600 series router, the following example configures link 4 to send test pattern 56.
interface atm 0/ima 2ima test link 2 pattern 56Related Command
show ima interface atm
Shows the currently configured test link and test pattern for an IMA group.
impedance
To specify the impedance (amount of wire resistance and reactivity to current) for an E1 link, enter the impedance interface configuration command. The setting must match the physical wiring. The no form of the command sets the default of 120-ohm.
impedance {75-ohm | 120-ohm}
no impedance {75-ohm | 120-ohm}
Syntax Description
120-ohm
Matches the unbalanced twisted-pair 120-ohm interface.
75-ohm
Matches the balanced BNC 750-ohm interface.
Default
120-ohm
Command Mode
Interface configuration
Command History
Command Usage
Impedance levels are maintained to avoid data corruption due to attenuation over long-distance links. The impedance is determined by the dongle-type cable that you plug in to the IMA module. Set this command to match that cable.
Example
On a Cisco 2600 or 3600 series router, the following example configures impedance at 120-ohm on ATM interface 0/2.
interface atm 0/2impedance 120-ohminterface atm ima
To configure an ATM IMA group and enter interface configuration mode, enter the interface atm ima global configuration command. If the group does not exist when the command is issued, the command automatically creates the group. The no form of the command removes the IMA group from the specified interface and removes all configurations and connections for the IMA group.
interface atm slot/imagroup-number
no interface atm slot/imagroup-number
Syntax Description
Default
By default there are no IMA groups, only individual ATM links.
Command Mode
Global configuration
Command History
Usage Guidelines
When a port is configured for IMA functionality, it no longer operates as an individual ATM link.
Specifying ATM links as members of a group by using the ima group interface command does not enable the group. You must use the interface atm ima command to create the group.
Example
On a Cisco 2600 or 3600 series router, the following example configures IMA group 0 on the module in slot 1:
interface atm 1/ima0 ip address 10.17.12.100Related Commands
loopback
To loop packets back to the interface for testing, enter the loopback interface configuration command with or without an optional keyword. The no form of the command removes the loopback.
loopback [line | local | payload | remote]
no loopback [line | local | payload | remote]
Syntax Description
Default
The default keyword is line.
Command Mode
Interface configuration
Command History
Usage Guidelines
You can use a loopback test on lines to detect and distinguish equipment malfunctions caused either by line and Channel Service Unit/Digital Service Unit (CSU/DSU) or by the interface. If correct data transmission is not possible when an interface is in loopback mode, the interface is the source of the problem.
The local loopback does not generate any packets automatically. Instead, the ping command is used.
Example
On a Cisco 2600 or 3600 series router, the following example sets up local loopback diagnostics:
interface atm 1/0 loopback localscrambling-payload
Scrambling improves data reliability by randomizing the ATM cell payload frames to avoid continuous non-variable bit patterns and improve the efficiency of ATM's cell delineation algorithms. The no form disables scrambling.
scrambling-payload
no scrambling-payload
Syntax Description
This command has no arguments or keywords.
Defaults
By default, payload scrambling is on for E1 links and off for T1 links.
Command Mode
Interface configuration
Command History
Usage Guidelines
Normally, you do not issue the scrambling-payload command explicitly, because the default value is sufficient. On T1 links, the default B8ZS line encoding normally assures sufficient reliability.
The scrambling setting must match that of the far end.
Example
On a Cisco 2600 or 3600 series router, the following example sets the link on interface 1 on the module in slot 0 to no scrambling:
interface atm0/1no scrambling-payloadshow controllers atm
Enter the privileged EXEC show controllers atm command, using a form that specifies the Inverse Multiplexing over ATM (IMA) group number to see information about an IMA group.
show controllers atm [slot//ima group-number]
Syntax Description
Default
No default behavior or values.
Command History
Release 11.2 GS
This command was added to support the Cisco 12000 series Gigabit Switch Routers.
12.0(5)T and 12.0(5)XK
This command was modified to support IMA groups.
Usage Guidelines
Use this command to monitor and diagnose ATM IMA links and groups.
Example
On a Cisco 2600 or 3600 series router, the following example displays detailed information about IMA group 0 on ATM interface 2.
router# show controller atm0/ima3Interface ATM0/IMA3 is upHardware is ATM IMALANE client MAC address is 0050.0f0c.148bhwidb=0x61C2E990, ds=0x617D498Cslot 0, unit 3, subunit 3rs8234 base 0x3C000000, slave base 0x3C000000rs8234 ds 0x617D498CSBDs - avail 2048, guaranteed 3, unguaranteed 2045, starved 0Seg VCC table 3C00B800, Shadow Seg VCC Table 617EF76C, VCD Table 61805798Schedule table 3C016800, Shadow Schedule table 618087C4, Size 63DRSM VCC Table 3C02ED80, Shadow RSM VCC Table 6180C994VPI Index Table 3C02C300, VCI Index Table 3C02E980Bucket2 Table 3C01E500, Shadow Bucket2 Table 6180A0E4MCR Limit Table 3C01E900, Shadow MCR Table 617D2160ABR template 3C01EB00, Shadow template 614DEEACRM Cell RS Queue 3C02C980Queue TXQ Addr Pos StQ Addr Pos0 UBR CHN0 3C028B00 0 03118540 01 UBR CHN1 3C028F00 0 03118D40 02 UBR CHN2 3C029300 0 03119540 03 UBR CHN3 3C029700 0 03119D40 04 VBR/ABR CHN0 3C029B00 0 0311A540 05 VBR/ABR CHN1 3C029F00 0 0311AD40 06 VBR/ABR CHN2 3C02A300 0 0311B540 07 VBR/ABR CHN3 3C02A700 0 0311BD40 08 VBR-RT CHN0 3C02AB00 0 0311C540 09 VBR-RT CHN1 3C02AF00 0 0311CD40 010 VBR-RT CHN2 3C02B300 0 0311D540 011 VBR-RT CHN3 3C02B700 0 0311DD40 012 SIG 3C02BB00 0 0311E540 013 VPD 3C02BF00 0 0311ED40 0Queue FBQ Addr Pos RSQ Addr Pos0 OAM 3C0EED80 255 0311F600 01 UBR CHN0 3C0EFD80 0 03120600 02 UBR CHN1 3C0F0D80 0 03121600 03 UBR CHN2 3C0F1D80 0 03122600 04 UBR CHN3 3C0F2D80 0 03123600 05 VBR/ABR CHN0 3C0F3D80 0 03124600 06 VBR/ABR CHN1 3C0F4D80 0 03125600 07 VBR/ABR CHN2 3C0F5D80 0 03126600 08 VBR/ABR CHN3 3C0F6D80 0 03127600 09 VBR-RT CHN0 3C0F7D80 0 03128600 010 VBR-RT CHN1 3C0F8D80 255 03129600 011 VBR-RT CHN2 3C0F9D80 0 0312A600 012 VBR-RT CHN3 3C0FAD80 0 0312B600 013 SIG 3C0FBD80 255 0312C600 0SAR Scheduling channels: -1 -1 -1 -1 -1 -1 -1 -1ATM channel number is 1link members are 0x7, active links are 0x0Group status is blockedNe, 3 links configured,Group Info: Configured links bitmap 0x7, Active links bitmap 0x0,Tx/Rx IMA_id 0x3/0x63,NE Group status is startUp,frame length 0x80, Max Diff Delay 0,1 min links, clock mode ctc, symmetry symmetricOperation, trl 0,Group Failure status is startUpNe.Test pattern procedure is disabledSAR counter totals across all links and groups:0 cells output, 0 cells stripped0 cells input, 0 cells discarded, 0 AAL5 frames discarded0 pci bus err, 0 dma fifo full err, 0 rsm parity err0 rsm syn err, 0 rsm/seg q full err, 0 rsm overflow err0 hs q full err, 0 no free buff q err, 0 seg underflow err0 host seg stat q full err
Related Commands
show ima interface atm
The show ima interface atm command provides information about all configured IMA groups or a specific group.
show ima interface atm [slot] /ima[group-number] [detail]
Note
Syntax Description
Default
No default behavior or values.
Command History
Usage Guidelines
Use this command to monitor the status of IMA group links.
Example
On a Cisco 2600 or 3600 series router, the following example displays detailed information about IMA group 0 on ATM interface 2. Without the detail keyword, only the information up to "Detailed group Information:" appears.
Router# show ima interface atm 4/ima0 detailInterface ATM2/IMA2 is upGroup index is 2Ne state is operational, failure status is noFailureactive links bitmap 0x30IMA Group Current Configuration:Tx/Rx configured links bitmap 0x30/0x30Tx/Rx minimum required links 1/1Maximum allowed diff delay is 25ms, Tx frame length 128Ne Tx clock mode CTC, configured timing reference link ATM2/4Test pattern procedure is disabledDetailed group Information:Tx/Rx Ima_id 0x22/0x40, symmetry symmetricOperationNumber of Tx/Rx configured links 2/2Number of Tx/Rx active links 2/2Fe Tx clock mode ctc, Rx frame length 128Tx/Rx timing reference link 4/4Maximum observed diff delay 0ms, least delayed link 5Running seconds 32GTSM last changed 10:14:41 UTC Wed Jun 16 1999IMA Group Current Counters (time elapsed 33 seconds):3 Ne Failures, 3 Fe Failures, 4 Unavail SecsIMA Group Total Counters (last 0 15 minute intervals):0 Ne Failures, 0 Fe Failures, 0 Unavail SecsDetailed IMA link Information:Interface ATM2/4 is upifIndex 13, Group Index 2, Row Status is activeTx/Rx Lid 4/4, relative delay 0msNe Tx/Rx state active/activeFe Tx/Rx state active/activeNe Rx failure status is noFailureFe Rx failure status is noFailureRx test pattern 0x41, test procedure disabledIMA Link Current Counters (time elapsed 35 seconds):1 Ima Violations, 0 Oif Anomalies1 Ne Severely Err Secs, 2 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs2 Ne Tx Unusable Secs, 2 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 2 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresIMA Link Total Counters (last 0 15 minute intervals):0 Ima Violations, 0 Oif Anomalies0 Ne Severely Err Secs, 0 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs0 Ne Tx Unusable Secs, 0 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 0 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresInterface ATM2/5 is upifIndex 14, Group Index 2, Row Status is activeTx/Rx Lid 5/5, relative delay 0msNe Tx/Rx state active/activeFe Tx/Rx state active/activeNe Rx failure status is noFailureFe Rx failure status is noFailureRx test pattern 0x41, test procedure disabledIMA Link Current Counters (time elapsed 46 seconds):1 Ima Violations, 0 Oif Anomalies1 Ne Severely Err Secs, 2 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs2 Ne Tx Unusable Secs, 2 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 2 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresIMA Link Total Counters (last 0 15 minute intervals):0 Ima Violations, 0 Oif Anomalies0 Ne Severely Err Secs, 0 Fe Severely Err Secs0 Ne Unavail Secs, 0 Fe Unavail Secs0 Ne Tx Unusable Secs, 0 Ne Rx Unusable Secs0 Fe Tx Unusable Secs, 0 Fe Rx Unusable Secs0 Ne Tx Failures, 0 Ne Rx Failures0 Fe Tx Failures, 0 Fe Rx FailuresRelated Command
show controllers atm
Displays detailed information about IMA groups and the links they include, as well as about current queues and ATM QoS settings.
Debug Command
This section documents a new debug command, debug ima.
debug ima
To display debug messages for IMA groups and links, enter the debug ima privileged EXEC command. Enter the no form of this command to disable debugging output.
[no] debug ima
Syntax Description
This command has no arguments or keywords.
Default
Debugging for IMA groups is not enabled.
Command History
Example
The following example shows output when you enter the debug ima command while adding two ATM links to an IMA group. Notice that the group has not yet been created with the interface atm slot/imagroup-number command, so the links are not activated yet as group members. However, the individual ATM links are deactivated.
Router# debug imaIMA network interface debugging is onRouter# config terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface atm1/0Router(config-if)# ima-group 1Router(config-if)#01:35:08:IMA shutdown atm layer of link ATM1/001:35:08:ima_clear_atm_layer_if ATM1/001:35:08:IMA link ATM1/0 removed in firmware01:35:08:ima_release_channel:ATM1/0 released channel 0.01:35:08:Bring up ATM1/4 that had been waiting for a free channel.01:35:08:IMA:no shut the ATM interface.01:35:08:IMA allocate_channel:ATM1/4 using channel 0.01:35:08:IMA config_restart ATM1/401:35:08:IMA adding link 0 to Group ATM1/IMA1ATM1/0 is down waiting for IMA group 1 to be activated01:35:08:Link 0 was added to Group ATM1/IMA101:35:08:ATM1/0 is down waiting for IMA group 1 to be created.01:35:08:IMA send AIS on link ATM1/001:35:08:IMA Link up/down Alarm:port 0, new status 0x10, old_status 0x1.01:35:10:%LINK-3-UPDOWN:Interface ATM1/4, changed state to up01:35:10:%LINK-3-UPDOWN:Interface ATM1/0, changed state to down01:35:11:%LINEPROTO-5-UPDOWN:Line protocol on Interface ATM1/4, changed state to up01:35:11:%LINEPROTO-5-UPDOWN:Line protocol on Interface ATM1/0, changed state to downRouter(config-if)# int atm1/1Router(config-if)# ima-group 1Router(config-if)#01:37:19:IMA shutdown atm layer of link ATM1/101:37:19:ima_clear_atm_layer_if ATM1/101:37:19:IMA link ATM1/1 removed in firmware01:37:19:ima_release_channel:ATM1/1 released channel 1.01:37:19:Bring up ATM1/5 that had been waiting for a free channel.01:37:19:IMA:no shut the ATM interface.01:37:19:IMA allocate_channel:ATM1/5 using channel 1.01:37:19:IMA config_restart ATM1/501:37:19:IMA adding link 1 to Group ATM1/IMA1ATM1/1 is down waiting for IMA group 1 to be activated01:37:19:Link 1 was added to Group ATM1/IMA101:37:19:ATM1/1 is down waiting for IMA group 1 to be created.01:37:19:IMA send AIS on link ATM1/101:37:19:IMA Link up/down Alarm:port 1, new status 0x10, old_status 0x1.Router(config-if)#01:37:21:%LINK-3-UPDOWN:Interface ATM1/5, changed state to up01:37:21:%LINK-3-UPDOWN:Interface ATM1/1, changed state to down01:37:22:%LINEPROTO-5-UPDOWN:Line protocol on Interface ATM1/5, changed state to up01:37:22:%LINEPROTO-5-UPDOWN:Line protocol on Interface ATM1/1, changed state to downRelated Commands
Glossary
AAL—ATM Adaptation Layer. Service-dependent sublayer of the data link layer. The AAL accepts data from different applications and presents it to the ATM layer in the form of 48-byte ATM payload segments. AALs consist of two sublayers: convergence sublayer (CS) and segmentation and reassembly (SAR). AALs differ on the basis of the source-destination timing used, whether they use constant bit rate (CBR) or variable bit rate (VBR), and whether they are used for connection-oriented or connectionless mode data transfer. At present, the four types of AAL recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5.
AAL1—ATM adaptation layer 1. One of four AALs recommended by the ITU-T. AAL1 is used for connection-oriented, delay-sensitive services requiring constant bit rates, such as uncompressed video and other isochronous traffic.
AAL5—ATM adaptation layer 5. One of four AALs recommended by the ITU-T. AAL5 supports connection-oriented VBR services and is used predominantly for the transfer of classical IP over ATM and LANE traffic. AAL5 uses simple and efficient AAL (SEAL) and is the least complex of the current AAL recommendations. It offers low bandwidth overhead and simpler processing requirements in exchange for reduced bandwidth capacity and error-recovery capability.
ABR—available bit rate. QoS class defined by the ATM Forum for ATM networks. ABR is used for connections that do not require timing relationships between source and destination. ABR provides no guarantees in terms of cell loss or delay, providing only best-effort service. Traffic sources adjust their transmission rate in response to information they receive describing the status of the network and its capability to successfully deliver data.
AIS—alarm indication signal. In a T1 transmission, an all-ones signal transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving terminal that there is a transmission fault that is located either at, or upstream from, the transmitting terminal.
ATM—Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
B8ZS—binary 8-zero substitution. Line-code type, used on T1 and E1 circuits, in which a special code is substituted whenever 8 consecutive zeros are sent over the link. This code is then interpreted at the remote end of the connection. This technique guarantees ones density independent of the data stream.
CBR—constant bit rate. QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery.
CPCS—common part convergence sublayer. One of the two sublayers of any AAL. The CPCS is service-independent and is further divided into the CS and the SAR sublayers. The CPCS is responsible for preparing data for transport across the ATM network, including the creation of the 48-byte payload cells that are passed to the ATM layer.
CS—convergence sublayer. One of the two sublayers of the AAL common part convergence sublayer (CPCS), which is responsible for padding and error checking. PDUs passed from the service specific convergence sublayer (SSCS) are appended with an 8-byte trailer (for error checking and other control information) and padded, if necessary, so that the length of the resulting PDU is divisible by 48. These PDUs are then passed to the SAR sublayer of the CPCS for further processing.
E1—European digital carrier facility used for transmitting data through the telephone hierarchy. The transmission rate for E1 is 2.048 megabits per second (Mbps).
E3—Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368 Mbps. E3 lines can be leased for private use from common carriers.
ESF—Extended Superframe. Framing type used on T1 circuits that consists of 24 frames of 192 bits each, with the 193rd bit providing timing and other functions. ESF is an enhanced version of SF.
FDL—Facility Data Link. A 4-Kbps channel, provided by the Extended SuperFrame (ESF) T1 framing format. The FDL performs outside the payload capacity and allows a service provider to check error statistics on terminating equipment, without intrusion.
ICP—IMA control protocol
ICMP—Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792.
ILMI—Interim Local Management Interface. Specification developed by the ATM Forum for incorporating network-management capabilities into the ATM User-Network Interface (UNI).
IMA—Inverse Multiplexing for ATM, a standard protocol defined by the ATM Forum in 1997.
IMA group—Physical links grouped to form a higher-bandwidth logical link whose rate is approximately the sum of the individual link rates.
ISDN—Integrated Services Digital Network. Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic.
NM—Network module.
OAM cell—Operation, Administration, and Maintenance cell. ATM Forum specification for cells used to monitor virtual circuits. OAM cells provide a virtual circuit-level loopback in which a router responds to the cells, demonstrating that the circuit is up, and the router is operational.
PDU—protocol data unit.
POTS—Plain Old Telephone Service. Basic telephone service supplying standard single-line telephones, telephone lines, and access to the public switched telephone network.
PVC—permanent virtual circuit. Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and tear down in situations where certain virtual circuits must exist all the time. In ATM terminology, called a permanent virtual connection.
QoS—quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.
SAR—segmentation and reassembly. One of the two sublayers of the AAL CPCS, responsible for dividing (at the source) and reassembling (at the destination) the PDUs passed from the CS. The SAR sublayer takes the PDUs processed by the CS and, after dividing them into 48-byte pieces of payload data, passes them to the ATM layer for further processing.
SF—Super Frame. Common framing type used on T1 circuits. SF consists of 12 frames of 192 bits each, with the 193rd bit providing error checking and other functions. SF is superseded by ESF, but is still widely used. Also called D4 framing.
SONET—Synchronous Optical Network. High-speed (up to 2.5 Gbps) synchronous network specification developed by Bellcore and designed to run on optical fiber. STS-1 is the basic building block of SONET.
SSCS—service specific convergence sublayer. One of the two sublayers of any AAL. SSCS, which is service dependent, offers assured data transmission. The SSCS can be null as well, in classical IP over ATM or LAN emulation implementations.
SVC—switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic. Called a switched virtual connection in ATM terminology.
T3—Digital WAN carrier facility. T3 transmits DS-3-formatted data at 44.736 Mbps through the telephone switching network.
UBR—unspecified bit rate. Quality of Service (QoS) class defined by the ATM Forum for ATM networks. UBR allows any amount of data up to a specified maximum to be sent across the network, but there are no guarantees in terms of cell loss rate and delay.
UNI—User-Network Interface. ATM Forum specification that defines an interoperability standard for the interface between ATM-based products (a router or an ATM switch) located in a private network and the ATM switches located within the public carrier networks. Also used to describe similar connections in Frame Relay networks.
VBR—variable bit rate. QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples, but that still need a guaranteed QoS.
VC—virtual circuit. Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel.
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