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
Guest
