Cisco OSM-12CT3/T1 - Optical Services Module Multiplexor, OSM-12CT3, OSM-12CT1 Configuration

CHAP T E R

7

Configuring the Channelized 12-port CT3/T1
Optical Services Modules

This chapter describes how to configure the 12-port channelized/unchannelized DS3 Optical Services
Modules (OSM-12CT3/T1).

The chapter consists of these sections:

• Understanding the Channelized/Unchannelized CT3/T1 Modules, page 7-1

• Supported Features, page 7-2

• Configuring the Interfaces, page 7-6

Understanding the Channelized/Unchannelized CT3/T1 Modules

The OSM-12CT3/T1 module provides 12DS3 interface connections using mini-SMB connectors.

Each DS3 port can be independently configured all the way from a clear channel DS3 down to and
including DS1, E1,and DS0 connections on the same port, with a maximum of 128 channels per DS3
port.

Each OSM-12CT3/T1 can support any combination of DS3/DS1/E1/T1s up to 1023 channels. For
example, each port can support the following:

• 1 DS3 at 44.7 Mbps

• 21 E1s at 2.048Mbps

• 28 DS1s at 1.5 Mbps

• 128 DS0s at 64 Kbps

An unchannelized DS3 connection provides a single serial interface data channel that may be configured
to use all of the DS3 bandwidth or a fractional portion of it. This mode is compatible with several
vendors of fractional (subrate) DS3 data service units (DSUs).

A cost, depending on the bandwidth, is associated with a serial interface. The total cost possible for 12 DS3

ports is 4096. That is, the sum of the costs of all the serial interfaces configured on 12 DS3 ports must be no

more than 4096. The show controller t3 command displays the VC cost, which indicates the available cost

of 12 DS3 ports. Tab le 7-1 shows the cost associated with each link type.

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Supported Features

Table 7-1 Serial Interface Cost

Link Type Cost

DS3 336

Unframed E1 16

1-6 DS-/TS 4

7-9 DS0/TS 6

10-16 DS0/TS 8

17-24 DS0/TS 12

25-31 TS 16

Channelized DS3 Overview

In the channelized mode of operation, an OSM-12CT3/T1 link is channelized into 28 DS1 or 21 E1 data
lines in an industry standard multiplexing format.

Each of the DS1 lines contain 24 timeslots of 64 or 56 kbps each, and each of the E1 lines contain 32
timeslots of 64 or 56 kbps each. The DS1and E1 lines can support one or more user data channels which
appear to the system as serial interfaces. Each serial interface is assigned one or more of the timeslots
giving the serial interface a bandwidth of n x 56 kbps or n x 64 kbps, where n is the number of timeslots
assigned. Any unused timeslots of the lines are filled with an idle channel pattern.

Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

Unchannelized DS3 Overview

In the unchannelized mode of operation, a DS3 link provides a single high speed user data channel,
rather than being multiplexed into 28 DS1 or 21 E1 lines. The data channel appears to the system as a
serial interface that may be configured to use the full DS3 bandwidth or a smaller portion of the DS3
bandwidth.

In unchannelized DS3 mode, the OSM-12CT3/T1 supports the maintenance data link (MDL) channel
when using c-bit parity framing as well as local and network loopbacks.

Supported Features

The 12-port channelized/unchannelized DS3 OSMs support the following features:

• General Features, page 7-3

• Serial Encapsulation Protocols, page 7-3

• DSU Mode, page 7-4

• T1 Configuration Options, page 7-4

• E1 Configuration Options, page 7-4

• DS3 Alarms, page 7-5

• Network Management, page 7-5

• Quality of Service Protocols, page 7-5

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Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

General Features

The general features are as follows:

• Channelized DS3 with 28 DS1 lines or 21 E1 lines multiplexed into a DS3 line.

• C-bit parity, M23, and auto-detect framing.

• Internal clocking configurable.

• Bit error rate test (BERT) diagnostics for each DS-3 channel

• Local, line, and remote loopback.

• Generation and termination of DS-3 maintenance data link (MDL) in C-bit framing.

• Compliance with ANSI T1.231-1993, Bellcore GR820, ANSI T1.107, ANSI T1.403 1989, G.703

Section 2, G.704 Section 3, AT&T Pub. 62411 1990, and Facilities Data Link (ANSI T1.403 and
AT&T 54016).

Serial Encapsulation Protocols

The OSMs support for the following serial encapsulation protocols:

• Point-to-Point Protocol (PPP)

Supported Features

• Distributed Multilink PPP (dMLPPP)

The OSM-12CT3/T1 module supports dMLPPP, which means that the MLPPP encapsulation is
performed on the OSM-12CT3/T1 module rather than the route processor. The following dMLPP
features are supported:

–

336 bundles per module

–

A maximum of 12 DS1/E1 channels per bundle

–

All links in a bundle should operate at the same speed

–

100 ms of differential delay

• High-Level Data Link Control (HDLC)

• Frame Relay

Configure the OSM-12CT3/T1 interfaces for Frame Relay as described in the Cisco IOS Wide-Area
Networking Configuration Guide, Release 12.1 under “Configuring Frame Relay” and in the Cisco
IOS Wide-Area Networking Command Reference, Release 12.1 at:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/wan_c/wcdfrely.htm

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/wan_r/wrdfrely.htm

Configure traffic shaping for Frame Relay as described in the Cisco IOS Quality of Service

Solutions Configuration Guide under “Configuring Distributed Traffic Shaping” at:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt4/qcfdts.h
tm.

For information on Multilink Frame Relay (FRF.16), see •Multilink Frame Relay (FRF.16),

page 1-4.

• MPLS/VPN

For MPLS/VPN configuration information, see Chapter 9, “Configuring Multiprotocol Label

Switching on the Optical Services Modules.”

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Supported Features

DSU Mode

Unchannelized DS-3 supports subrate and scrambling formats for the following DSUs.

• Digital Link

• Ve ri l in k

• Adtran

• Larscom

• Kentrox

T1 Configuration Options

The T1 lines have the following configuration options:

• Local, line, and remote loopback.

• Generation and termination of DS-3 maintenance data link (MDL) in C-bit framing.

• In T1 mode, the channelized CT3/T1 OSMs support facilities data link (FDL) in Extended

Superframe (ESF) framing, as well as various loopbacks. Bit error rate testing (BERT) is supported
on each of the T1 lines. It can be done over a framed or unframed DS-1 signal. The
OSM-ChOC12C/T1 module has four framers, each connected to three contiguous ports. BER testing
can be done simultenously on 6 T1 interfaces in addition to any DS3 interfaces configured on the
three ports to which a framer is connected.

Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

• In the channelized mode of operation, a channelized CT3/T1 OSM link can be channelized into

maximum of 336 T1 data lines in an industry standard multiplexing format. Each of the T1 lines
contains 24 timeslots of 64 or 56 kbps each. The T1 lines can support one or more user data
channels, which appear to the system as serial interfaces. Each serial interface is assigned one or
more of the timeslots giving the serial interface a bandwidth of n x 56 kbps or n x 64 kbps, where n
is the number of timeslots assigned. Any unused timeslots of the T1 are filled with an idle channel
pattern.

E1 Configuration Options

The E1 lines have the following configuration options:

• Channelized E1—Any of the 21 E1 lines can be configured as channelized E1 lines, but you are

limited to a total of 128 logical channels. You can group the time slots in these E1 lines into several
individual logical channel groups, each of which carries data with different data link layer protocol
encapsulations. You can configure timeslot 16 as a data channel, although it is typically used for
common channel signaling. (Channel associated signaling (CAS) for voice channels and E1
Facilities Data Link [FDL] on timeslot 16 are not supported.)

• Each logical channel group can be composed of individual 64-kbps timeslots and/or ranges of

timeslots, for example, 1, 9, 12-14. Each logical channel group can contain from 1-31 timeslots
maximum; the same timeslot cannot be used in more than one logical channel group. Any unused
timeslots are filled with programmable idle-channel data.

• Fractional E1— Any of the 21 E1 lines can be configured as fractional E1 lines, each of which can

be either E1 frames or E1 cyclic redundancy check (CRC) multiframes, as specified by CCITT/ITU
G.704 and G.706. A fractional E1 line is a subset of the full E1 bandwidth, which uses n x 64 kbps;
where n is a timeslot in the range of 1-31.

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Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

Fractional E1 lines contain only a single logical channel group that can be either a single 64-kbps
timeslot or a range of timeslots; for example timeslot 1, or timeslots 15-23. Any unused timeslots
are filled with programmable idle-channel data.

Note If you assign only one channel group to an E1 line, it is a fractional E1 line. If you assign

more than one channel group to an E1 line, it is a channelized E1 line.

• Unframed E1—Any of the 21 E1 lines can be configured as unframed E1 data lines. Each unframed

E1 line contains no framing overhead and is not timeslot divided.

Note For channelized, fractional, and unframed configurations each configured channel group, which might

contain individual timeslots and/or ranges of timeslots, uses only one of the 128 available logical
channels. For example, if you assign the range of timeslots 3-7 to a channel group, only one logical
channel is used. Likewise, if you assign just timeslot 3 to a channel group, only one logical channel is
used.

DS3 Alarms

Supported Features

This section lists the supported DS3 alarms:

• Alarm indication signal (AIS)

• Out of frame (OOF)

• Far End Remote Failure (FERF)

• Loss of Signal (LOS)

• Far End Block Errors (FEBE)

• Far-End Alarm and Control (FEAC) support

Network Management

This section lists the supported network management features:

• Local Loopback.

• Network Loopback.

• RFC 1407 MIB support.

Quality of Service Protocols

For information on configuring QoS on the Channelized OSMs, refer to Chapter 10, “Configuring QoS

on the Optical Services Modules.”

The following QoS features are supported on the Channelized OSMs:

• Hierarchical traffic shaping for Frame Relay, HDLC, and PPP encapsulations

• PFC2 QoS on the LAN and WAN ports

• Differentiated Services Control Point (DSCP)

• IP Precedence classification

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Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

Configure class-based marking as described in the Class-Based Marking Feature Module at this
URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/cbpmark2
.htm

• Classification and priority marking based on the following:

–

Ethertype

–

IP Source Address (SA)

–

IP Destintation Address (DA)

–

TCP port number

–

UDP port number

–

IP SA + TCP/UDP port number + IP DA + TCP/UDP port number

• Class-based weighted fair queuing (CBWFQ) on the WAN ports.

• Low latency queuing (LLQ) on the WAN ports.

For general information on classification, marking, and queuing in IOS, refer to the “Classificiation”
chapter of the Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.1 at this
URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_c/index.htm

For information about platform-independent IOS QoS commands, refer to the Cisco IOS Quality of
Service Solutions Command Reference, Release 12.1at this URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_r/index.htm

Configuring the Interfaces

This chapter includes these sections:

• Configuring the T3 Controller, page 7-6

• Configuring the Unchannelized DS3 Interface, page 7-7

• Configuring the Channelized DS3 Interface, page 7-9

• Configuring Distributed MLPPP, page 7-11

• Configuring the T1/NxDS0 Lines, page 7-9

• Configuring the E1 Lines, page 7-10

Configuring the T3 Controller

To configure the controller, perform this task:

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Command Purpose

Step 1

Step 2

Step 3

Step 4

Step 5

Router# configure terminal

Router(config)# controller t3 slot/port

Router(config-controller)# [no] channelized [mode {t1
| e1}]

Router(config-controller)# [no] bert pattern
[2^11 | 2^15 | 2^20 O.153 | 2^20 QRSS | 2^23 | 0s |
1s | alt-0-1] interval [1-1440]

Router(config-controller)# [no] mdl string {eic | fic |
generator | lic | pfi | port | unit}

Configuring the Interfaces

Enters configuration mode and specifies that the
console terminal is the source of the configuration
subcommands.

Selects a port and enters controller configuration
mode.

Specifies the channelization mode.

no channelized—configures the interface as
unchannelized.

channelized mode t1—configures the interfaces
for T1 channelized mode

channelized mode e1—configures the interfaces
for E1 channelized mode

Default is t1.

(Optional) Configures bit-error-rate (BER)
testing.

(Optional) Specifies the maintenance data link
(MDL) messages.

eic—equipment ID code
fic—frame ID code
generator—generator number in MDL test signal
lic—location ID code
pfi—facility ID code in MDL path message
port—port number in MDL idle string message
unit—unit code

Step 6

Step 7

Step 8

Router(config-controller)# [no] mdl transmit
{path | idle-signal | test-signal}

Router(config-controller)# t1 1 bert channel-group 0

pattern 2^11 interval 1

Router(config-controller)# t1 1 bert timeslots 21,24
pattern 2^11 interval 1

This example shows how to configure the controller:

Router# configure terminal
Router(config)# controller T3 3/0
Router(config-controller)# no channelized
Router(config-controller)# exit
Router(config)#

Configuring the Unchannelized DS3 Interface

After you verify the controller configuration, you can configure the associated DS3 interfaces.

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Default is no mdl string.

(Optional) Enables MDL message transmission.

Default is no mdl transmit.

(Optional) Configures bit error rate testing on
channel-group 0 (all timeslots under channel
group 0).

(Optional) Configures bit error rate testing on
timeslots 21 and 24 only.

7-7

Configuring the Interfaces

Note IP addresses can not be assigned to main interfaces configured for Frame Relay.

Command Purpose

Step 1

Step 2

Step 3

Step 4

Router# configure terminal

Router(config)# interface serial slot/port

Router(config-if)# framing {c-bit | m23}

Router(config-if)# [no] dsu bandwidth Kilobits/sec

Router(config-if)# [no] dsu mode {0 | 1 | 2 | 3 | 4}

Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

To configure the unchannelized DS3 interfaces, perform this task:

Enters configuration mode and specifies that the
console terminal is the source of the configuration
subcommands.

Specifies the serial port to configure.

Specifies the framing.

Sets the DSU subrate bandwidth.

Specifies the DSU mode:

0–Digital-Link

1–Kentrox

2–Larscom

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

Step 11

Router(config-if)# [no] dsu remote [accept | fullrate]

Router(config-if)# encapsulation hdlc | ppp

Router(config-if)# [no] clock source {internal | line}

Router(config-if)# [no] loopback
{local | network | remote {line | payload}}

Router(config-if)# [no] cablelength feet

Router(config-if)# [no] keepalive

Router(config-if)# no shutdown

This is an example of an unchannelized DS3 interface configuration:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# controller t3 3/0
Router (config-controller)# no channelized
Router (config-controller)# exit
Router (config)# interface serial 1/0
Router (config-if)# dsu bandwidth 16000
Router (config-if)# encapsulation ppp
Router (config-if)# no shutdown
Router (config-if)# exit
Router(config)#

3–Adtran

4–Verilink

Specifies if the local (near-end) interface will
accept incoming requests from the remote
(far-end) interface, or if the local interface will
request that the remote interface set its bandwidth to
fullrate.

Specifies the encapsulation type. HDLC is the
default encapsulation.

(Optional) Specifies the clock source.

Default is line.

(Optional) Sets the loopback mode.

Default is no loopback.

Specifies the cable length. Default is 224.

Turns on and off keepalive messages.

Enables the interface.

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Configuring the Channelized DS3 Interface

The DS3 Interface can be channelized down to T1 and E1 links. These sections provide configuration
information for T1 and E1 link configuration:

• Configuring the T3 Controller for Channelization, page 7-9

• Configuring the T1/NxDS0 Lines, page 7-9

• Configuring the E1 Lines, page 7-10

Note Bit error rate testing (BERT) is supported on each of the T1 and E1 lines. It can be done over a framed

or unframed DS-1 signal. The OSM-12CT3/T1 module has four framers, each connected to three
contiguous ports. BER testing can be done simultenously on 6 T1 or E1 interfaces in addition to any DS3
interfaces configured on the three ports to which a framer is connected.

Note BERT channel-groups and timeslots are also supported.

Configuring the Interfaces

Configuring the T3 Controller for Channelization

To configure the T3 controller for T1 of E1 channelization, perform this task:

Command Purpose

Step 1

Step 2

Step 3

Router# configure terminal

Router(config)# controller slot/port

Router (config-controller)# [no] channelized [mode {t1
| e1}]

This example configures the T3 controller for T1 channelization mode:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# controller T3 2/0
Router(config-controller)# channelized mode t1
Router(config-controller)# CNTL/Z
Router#

Configuring the T1/NxDS0 Lines

Enters configuration mode and specifies that the
console terminal is the source of the configuration
subcommands.

Selects the controller.

Specifies the channelization mode.

Default is t1.

To configure T1/NxDS0 lines, perform this task:

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Configuring the Interfaces

Command Purpose

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

Step 11

Router# configure terminal

Router(config)# controller t3 slot/port

Router(config-controller)# [no] t1 t1-number

channel-group channel-group-number timeslots
list-of-timeslots [speed 56 | 64]

Router (config-if)# [no] t1 t1-number framing {sf |
esf}

Router (config-controller)# [no] t1 t1-number fdl ansi

Router (config-controller)# [no] t1 t1-number yellow
{detection | generation}

Router (config-controller)# [no] t1 t1-number clock
source {internal | line}

Router (config-controller)# [no] t1 t1-number loopback
{local | network | remote {line fdl {ansi | bellcore}|
payload fdl ansi}}

Router (config-controller)# [no] [e1 | t1] [e1-number
| t1 number] bert pattern {2^11 | 2^15 | 2^20 O.153
| 2^20 QRSS | 2^23 | 0s | 1s | alt-0-1} interval
[1-1440]

Router(config-controller)# exit

Router(config)# [no] interface serial slot/port/t1

number: channel-group number

Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

Enters configuration mode and specifies that the
console terminal is the source of the configuration
subcommands.

Enters controller configuration mode.

Configures the channel group.

Specifies the framing.

(Optional) Enables the once-second transmission
of the remote performance reports via facility data
link (FDL).

(Optional) Enables detection and generation of T1
yellow alarms.

(Optional) Defines clock source for the specified
T1 line.

(Optional) Sets the loopback mode.

(Optional) Configures bit-error-rate (BER)
testing.

Exits controller configuration mode.

Selects the interface and configures the channel
group.

This example configures a T1/NxDS0 line:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# controller T3 3/1
Router(config-controller)# t1 6 channel-group 0 timeslots 1-5, 20-23
Router(config-controller)# t1 6 framing sf
Router(config-controller)# t1 6 clock source line
Router(config-controller)# t1 6 loopback remote line
Router(config-controller)# t1 6 bert pattern 2^23 interval 5 unframed
Router(config-controller)# exit
Router(config)# interface serial t1 3/1/6:0
Router (config-if)# CNTL/Z
Router#

Configuring the E1 Lines

To configure E1 lines, perform this task:

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Command Purpose

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

Step 11

Step 12

Router# configure terminal

Router(config)# controller slot/port

Router (config-controller)# [no] channelized [mode {t1
| e1}]

Router (config-controller)# [no] e1 e1number clock
source {internal | line}

Router (config-controller)# [no] e1 e1 number unframed

Router (config-controller)# [no] e1 e1 number
framing {crc4 | no-crc4}

Router (config-controller)# [no] e1 e1 number national

bits pattern

Router (config-controller)# [no] e1 e1 number
channel-group channel-group number timeslots

list-of-timeslots speed [56 | 64]

Router (config-controller)# [no] e1 e1 number loopback
{local | network}

Router (config-controller)# [no] [e1 | t1] [e1 number
| t1 number] bert pattern {2^11 | 2^15 | 2^20 O.153
| 2^20 QRSS | 2^23 | 0s | 1s | alt-0-1} interval
[1-1440]

Router(config-controller)# exit

Router(config)# [no] interface serial slot/port/t1

number: channel-group number

Configuring the Interfaces

Enters configuration mode and specifies that the
console terminal is the source of the configuration
subcommands.

Selects the controller.

Specifies the channelization mode.

Default is t1.

Defines clock source for the specified E1 line.

Configures the E1 line as unframed.

Specifies the framing.

Specifies the national bits reserved for
country-specific control information.

Configures a channel-group.

(Optional) Sets the loopback mode.

(Optional) Configures bit-error-rate (BER)
testing.

Exits controller configuration mode.

Selects the interface and configures the channel
group.

This example configures an E1 line:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router)# controller T3 4/1
Router(config-controller)# channelized mode e1
Router(config-controller)# e1 10 channel-group 0 timeslots 1-5, 20-23
Router(config-controller)# e1 10 framing crc4
Router(config-controller)# e1 10 national bits
Router(config-controller)# e1 10 clock source line
Router(config-controller)# e1 10 loopback network line
Router(config-controller)# e1 10 bert pattern 2^23 interval 5 unframed
Router (config-controller)# exit
Router(config)# interface serial e1 4/0/10:0
Router(config-if)# CNTL/Z
Router#

Configuring Distributed MLPPP

Distributed MLPPP allows you to combine T1 or E1 lines into a bundle that has the combined bandwidth
of multiple T1 or E1 lines. Bundling T1 or E1 lines enables you to increase the bandwidth of your
network links beyond that of a single T1 or E1 line without having to purchase a T3 line.

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Configuring the Interfaces

Figure 7-1 shows a network using an MLPPP link. The Cisco 7600 Series router is connected to the

network with an OSM-12CT3/T1 module. An OSM-12CT3/DS interface has been configured with
MLPPP to carry two bundles of four T1 lines each. Each of these bundles goes out to separate remote
Cisco 7200 series routers, which each have one MLPPP bundle of four T1 lines. Another
OSM-12CT3/DS interface has been configured with MLPPP to carry two bundles of two T1 lines. One
of these bundles goes out to a Cisco 2500 series router and the other goes out to a Cisco 3800 series
router.

Figure 7-1 MLPPP Topology

Chapter 7 Configuring the Channelized 12-port CT3/T1 Optical Services Modules

Cisco 7200

T1s

T1s

Cisco 7200

Creating a Multilink Bundle

To create a multilink bundle, perform this task beginning in global configuration mode:

Command Purpose

Step 1

Step 2

Step 3

Step 4

Step 5

Router(config)# interface multilink

bundle-id

Router(config-if)# ip address address
mask

Router(config-if)# encapsulation ppp

Router(config-if)# ppp multilink

Router(config-if)# [no] multilink-group

bundle-id

PSTN

Channelized T3

with two bundles

Cisco 7600

with OSM-12CT3/DS0

CT3 CT3

Channelized T3

of four T1

with two bundles

of two T1s each

Statically configures link bundles.

Note The Multilink PPP command is available on serial

interfaces only.

Assigns an IP address to the multilink interface.

Enables PPP encapsulation.

(Optional) Enables Multilink PPP.

(Optional) Designates an interface as part of a multilink bundle.

bundle-id is the bundle number created with the interface multilink
bundle-id command.

Cisco 2500

Cisco 3800

77983

The following example shows how to create a multilink bundle:

Router(config)# interface multilink 1
Router(config-if)# ip address 10.0.0.0 10.255.255.255
Router(config-if)# encapsulation ppp
Router(config-if)# ppp multilink
Router(config-if)# multilink-group 1
Router(config-if)# CNTL/Z
Router#

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Assigning an Interface to a Multilink Bundle

To assign an interface to a multilink bundle, use the following commands in interface configuration
mode:

Command Purpose

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Router(config)# interface serial

slot/port/DS0 number: channel-group number

Router(config-if)# no ip address

Router(config-if)# encapsulation ppp

Router(config-if)# multilink-group

bundle-id

Router(config-if)# ppp authentication chap

Router(config-if)# ppp chap hostname name

Selects the interface.

Removes any specified IP address.

Enables PPP encapsulation.

Designates an interface as part of a multilink bundle.

bundle-id is the bundle number created with the interface multilink
bundle-id command.

(Optional) Enables Challenge Handshake Authentication Protocol
(CHAP) authentication.

(Optional) Enables the presence of multiple bundles between two
hosts.

Configuring the Interfaces

The following example shows how to create a multilink interface and add it to a multilink bundle:

Router(config)# interface serial 1/0/0:1
Router(config-if)# no ip address
Router(config-if)# encapsulation ppp
Router(config-if)# multilink-group 1
Router(config-if)# CNTL/Z
Router#

Enabling PPP Multilink Fragmentation

By default, PPP multilink fragmentation is enabled. To enable PPP multilink fragmentation after it has
been disabled, perform this task in interface configuration mode:

Command Purpose

Router(config-if)# [no] ppp multilink
fragmentation

Router(config-if)# [no] multilink fragment-delay

milliseconds

Enabling fragmentation reduces the delay latency among bundle links, but adds some load to the CPU.
Disabling fragmentation may result in better throughput.

Enables fragmentation. By default fragmentation is enabled.

Specifies the tolerable delay in sending the fragment on the
multilink. This delay is used to compute fragment size of the
packet. Three supported fragment sizes are 128, 256, 512. Default
delay is 30ms.

If your data traffic is consistently of a similar size, we recommend disabling fragmentation. In this case,
the benefits of fragmentation may be outweighed by the added load on the CPU.

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Configuring the Interfaces

Configuring Multilink PPP Minimum Links Mandatory

To configure the Multilink PPP Minimum Links Mandatory feature, use the following commands in
interface configuration mode:

Command Purpose

Step 1

Step 2

Router(config-if)# ppp multilink

Router(config-if)# multilink min-links

links mandatory

This example shows how to configure the Multilink PPP Minimum Links Mandatory feature:

Router(config-if)# ppp multilink
Router(config-if)# multilink min-links 5 mandatory

Enables Multilink PPP.

Specifies the required minimum number of links in a Multilink
PPP (MLP) bundle. If the minimum number of links in the MLP
bundle falls below the number specified by the links attribute, the
MLP bundle is disabled.

• links—Minimum number of links, in the range 0 to 12.

• The mandatory keyword is required on the OSM-12CT3/T1.

For additional information about the Multilink PPP Minimum Links Mandatory feature, refer to this
URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121limit/121e/121
e11/12e_mlp.htm#xtocid0

The commands listed at this URL are all supported on the OSM-12CT3/T1, except the following:

• multilink max-link

• multilink load-threshold

• multilink max-fragments

• debug ppp multilink fragments

Verifying the Configuration

Use the show ppp multilink command to display information about the newly created multilink bundle:

Router# show ppp multilink

Multilink1, bundle name is group1
Bundle is Distributed
0 lost fragments, 0 reordered, 0 unassigned, sequence 0x0/0x0 rcvd/sent
0 discarded, 0 lost received, 1/255 load
Member links:4 active, 0 inactive (max not set, min not set)

Serial1/0/0:1

Creating a Multilink Interface Example

Interface multilink1
ip address 100.0.0.1 255.255.255.0

interface serial6/12/1:0
no ip address
encapsulation ppp

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ppp chap hostname mul1
multilink-group 1

interface serial6/12/2:0
no ip address
encapsulation ppp
ppp chap hostname mul1
multilink-group 1

interface serial6/12/3:0
no ip address
encapsulation ppp
ppp chap hostname mul1
multilink-group 1

show ppp multilink

Multilink1, bundle name is mul1
Bundle up for 19:58:37
Bundle is Distributed
0 lost fragments, 0 reordered, 0 unassigned
0 discarded, 0 lost received, 1/255 load
0x0 received sequence, 0x0 sent sequence
Member links:3 active, 0 inactive (max not set, min not set)
Serial6/12/1:0, since 19:58:37, no frags rcvd 384 weight
Serial6/12/2:0, since 19:58:37, no frags rcvd 384 weight
Serial6/12/3:0, since 19:58:37, no frags rcvd 384 weight

Configuring the Interfaces

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