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# Configuring Performance Rate of Line Modules on ERX-7xx Models and the ERX-1410 Router

| Note: The information in this section does not apply to the ERX-1440 router, ERX-310 router, E120 router, or the E320 router. It also does not apply to the OC48 line module, which is supported only by the ERX-1440 router.

Line modules in an ERX-1440 router or an ERX-310 router always operate at line rate performance. However, you can configure ERX-7xx models and the ERX-1410 router to enable the line modules either to operate at full line rate performance or to allow line modules to operate at a rate dependent on the resources available.

Operating at full line rate performance restricts the combination of line modules in the router. Operating at a rate dependent on the resources available allows a much more extensive combination of line modules in the router and is known as bandwidth oversubscription.

To configure performance:

1. Choose a combination of line modules appropriate for the performance. See Choosing a Combination of Line Modules.
2. Disable slots that contain unwanted line modules, or modify the combination of line modules in the router. See Disabling and Reenabling Line Modules, SRP Modules, and SFMs, and ERX Hardware Guide, Chapter 4, Installing Modules.
3. Specify the type of performance. See Specifying the Type of Performance.

## Choosing a Combination of Line Modules

For line rate performance, the total bandwidth required by the line modules in the slot group must not exceed the bandwidth available from the SRP module. In this case, the combination of line modules that can reside in a slot group depends on the following:

- The number of slots per group
- The bandwidth available from the SRP module
- The bandwidth required by each line module
- In the case of the SRP-5G+ and SRP-10G modules, the switches (upper and lower) that the line module can use.

### Slot Groups

The number of slots in a group depends on the E-series model. For information about slot groups, see ERX Hardware Guide, Chapter 4, Installing Modules.

### SRP Modules Bandwidth

Different SRP modules offer different bandwidths:

- The SRP-10G module provides 2.5 Gbps bandwidth per slot group.
- The SRP-5G+ module (ERX-705 router only) provides:
  - 2.5 Gbps bandwidth per slot group
  - 5 Gbps bandwidth per router

### Line Modules Bandwidth and Switch Usage

The SRP-5G+ and SRP-10G modules comprise two switches; each switch provides 50 percent of the bandwidth.

The line modules in a slot group cannot operate at line rate if:

- The sum of their bandwidths exceeds the bandwidth that the SRP module can supply per slot group.
- The sum of the bandwidths they require from one SRP switch exceeds the bandwidth that the SRP switch can supply per slot group.

Table 38 shows the bandwidth that each line module requires for line rate performance and the switches that the line module can use on the SRP-5G+ and SRP-10G modules.

Table 38: Bandwidth Statistics for Line Modules

Line Module | Total Bandwidth Required (Gbps) | Switches Used on SRP-5G+ and SRP-10G Modules
--- | --- | ---
cOCx/STMx | 2.46 | Both switches
COCX-F3 | 2.46 | Both switches
CT3/T3-F0 | 2.46 | Both switches
GE/FE | 2.46 | Both switches
IPSec Service | 2.46 | Both switches
OC3/STM1 GE/FE | 2.46 | Both switches
OCx/STMx ATM | 1.22 | Both switches
OCx/STMx POS | 2.46 | Both switches

### Allowed Combinations for Line Rate Performance

The SRP-5G+ and SRP-10G modules support all the line modules listed in Table 38.

Only certain combinations of line modules allow line rate performance (see Table 39 through Table 41). However, if performance lower than line rate is acceptable, you can use any combination of line modules in a slot group.

For example, the SRP-10G module offers a total bandwidth of 2.5 Gbps for each slot group. The GE line module requires 2.46 Mbps bandwidth for operation at line rate, and can use both switches in the SRP-10G module. If you require line rate from a GE line module, install only one GE line module in the slot group. However, if lower performance is acceptable, you can install two or three GE line modules in a slot group and enable bandwidth oversubscription.

When bandwidth oversubscription is enabled, all line modules optimize use of the resources available. For example, if two GE line modules are installed in a slot group, each line module is allocated 50 percent of the available bandwidth. However, if one line module is using less bandwidth than it is allocated, the other line module can use more bandwidth than it is allocated and can operate at a greater rate.

Table 39, Table 40, and Table 41 indicate combinations of line modules that allow line rate performance.

Table 39: Combinations of Line Modules for Line Rate Performance—SRP-10G Module in an ERX-7xx Model

Possible Combinations of Line Modules | Examples of Allowed Combinations | Examples of Forbidden Combinations
--- | --- | ---
One supported line module and one empty slot in slot group 1 NOTE: The SRP-10G module supports all line modules listed in Table 38. Two OCx/STMx ATM line modules in slot group 1 One supported line module in slot groups 2, 3 and 4 | One OCx/STMx POS line module in slot group 1, a GE/FE line module in slot group 2, and one OCx/STMx ATM line module in slot group 4 Two OCx/STMx ATM line modules in slot group 1, one GE/FE line module in slot group 2, and one SM in slot group 3 | A GE/FE line module and any other line module in slot group 1 Two OCx/STMx POS line modules in slot group 1

Table 40: Combinations of Line Modules for Line Rate Performance—SRP-10G Module in an ERX-1410 Router

Possible Combinations of Line Modules | Examples of Allowed Combinations | Examples of Forbidden Combinations
--- | --- | ---
One supported line module and two empty slots in any slot group NOTE: The SRP-10G module supports all line modules listed in Table 38. Two OCx/STMx ATM line modules and one GE/FE module and one empty slot in any slot group (bandwidth oversubscription enabled) One OC3/STM1 GE/FE module in any slot (bandwidth oversubscription disabled) | One COCX-F3 line module in slot group 1, a GE/FE line module in slot group 2, and a OCx/STMx POS line module in slot group 3 | Three OCx/STMx ATM line modules in any slot group Two GE/FE line modules in any slot group

Table 41: Combinations of Line Modules for Line Rate Performance—SRP-5G+ Module in an ERX-705 Router

Possible Combinations of Line Modules In Slot Groups | Examples of Allowed Combinations | Examples of Forbidden Combinations
--- | --- | ---
NOTE: The total bandwidth of all line modules must not exceed 5 Gbps. To make optimal use of the available bandwidth, put line modules that require maximum bandwidth in slot 2, 3, or 4.
One supported line module and one empty slot in slot group 1 NOTE: The SRP-5G+ module supports all line modules listed in Table 38. Two OCx/STMx ATM line modules in slot group 1 One cOCx/STMx, COCX-F3, CT3/T3 FO, GE/FE, IPSec Service, or OCx/STMx line module in slot groups 2, 3, and 4 | Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, and a GE/FE line module (2.46 Gbps) in slot group 4 Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, and a COCX-F3 line module in slot group 2 | Two OCx/STMx ATM line modules (total 2.44 Gbps) in slot group 1, a GE/FE line module (2.46 Gbps) in slot group 3, and an OCx/STMx POS line module (2.46 Gbps) in slot 4 (violates chassis limitation) Two OCx/STMx POS line modules (total 4.92 Gbps) in slot group 1 (violates slot group limitation)

## Specifying the Type of Performance

After you have installed a suitable combination of line modules, you can specify a different type of performance. To specify the type of performance:

1. Issue the show bandwidth oversubscription command.
2. If the setting is not the one you want, enable or disable bandwidth oversubscription.
3. Reboot the router.

bandwidth oversubscription

- Use to enable bandwidth oversubscription for an ERX-7xx model or ERX-1410 router. Reboot the router after you have issued this command to change the bandwidth oversubscription status.
- By default, bandwidth oversubscription is enabled.
- Example
  `
  host1(config)#bandwidth oversubscription
  `
- Use the no version to disable bandwidth oversubscription. Reboot the router after you have issued this command to change the bandwidth oversubscription status.
- See bandwidth oversubscription.

## Monitoring Bandwidth Oversubscription

Use the show bandwidth oversubscription and show utilization (see Monitoring Modules) commands to monitor the status of bandwidth oversubscription.

show bandwidth oversubscription

- Use to display the bandwidth oversubscription status for an ERX-7xx model or ERX-1410 router.
- Example 1: This example shows the display when bandwidth oversubscription is enabled.

      host1#show bandwidth oversubscription
      Bandwidth oversubscription is currently in effect.

- Example 2: This example shows the display that appears after you issue the no bandwidth oversubscription command to disable bandwidth oversubscription.

      host1#no bandwidth oversubscription
      host1#show bandwidth oversubscription
      Bandwidth oversubscription is currently in effect.
      Bandwidth oversubscription will not be in effect the next time the system reboots.

- Example 3: This example shows the display when bandwidth oversubscription is disabled.

      host1#show bandwidth oversubscription
      Bandwidth oversubscription is currently not in effect.

- Example 4: This example shows the display that appears after you issue the bandwidth oversubscription command to enable bandwidth oversubscription.

      host1#bandwidth oversubscription
      host1#show bandwidth oversubscription
      Bandwidth oversubscription is currently not in effect.
      Bandwidth oversubscription will be in effect the next time the system reboots.

- See show bandwidth oversubscription.

## Troubleshooting Bandwidth Oversubscription

If you enter a forbidden combination of line modules or exceed the slot group bandwidth when you have not configured bandwidth oversubscription, you will see an error message.

For example, suppose you originally configure the router for bandwidth oversubscription and then want to change to full line rate performance. You forget to remove line modules or disable slots, and enter the no bandwidth oversubscription command. The following message appears:

`

host1(config)#no bandwidth oversubscription
% failed : bandwidth over subscribed at slot 0-2

`

To resolve the problem, remove the unwanted line modules, or disable the slots that contain those line modules.

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