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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 2 Scalability and Performance
Configuring the Cisco 10000 Series Router for High Scalability
Configuring the Trunk Interface Input Hold Queue
To ensure high scalability, set the trunk interface input hold queue to a high value (Example 2-13).
Note The default value for the OC-12 ATM line card trunk interface input hold queue is 27230. Cisco
laboratory tests have shown this setting to result in the highest scalability for the OC-12 ATM line card.
We recommend that you not change the default setting.
Example 2-13 Setting the Trunk Interface Input Hold Queue
Router(config)# interface gig1/0/0
Router(config-if)# hold-queue 4096 in
Configuring no atm pxf queuing
Note We do not recommend using this mode for QoS-sensitive deployments.
Configuring the no atm pxf queuing command on each port of the Cisco 10000 series router enables
the router to support a high number of VCs. PPPoA supports one session per VC and requires that you
enable no atm pxf queuing to support 32,000 PPPoA sessions. Enabling no atm pxf queuing is not
required for L2TP, and might not be required for PPPoE, because you can have 32,000 sessions on a
single VC.
The Cisco 10000 series router supports three ATM traffic classes when you configure no atm pxf
queuing: unshaped UBR (no PCR is specified), shaped UBR (PCR is specified), and VBR-nrt. To
configure an unspecified bit rate (UBR) quality of service (QoS) and specify the output peak cell rate
(PCR), use the ubr command in the appropriate configuration mode. In ATM VC configuration mode,
the syntax is:
Router(config-if-atm-vc)# ubr output-pcr
If you do not specify a PCR, unshaped UBR is configured.
To configure the variable bit rate-nonreal-time (VBR-nrt) QoS, use the vbr-nrt command in the
appropriate configuration mode and specify the output PCR, output sustainable cell rate (SCR), and the
output maximum burst cell size (MBS) for a VC class. Note that if the PCR and SCR values are equal,
the MBS value is 1.
output-pcr output-scr output-mbs
Note Before you configure VCs on an interface, configure the atm pxf queuing mode for the port
(atm
pxf queuing or no atm pxf queuing). After you configure the mode, then configure the VCs. Do
not change the mode while VCs are configured on the interface. If you need to change the mode, delete
the VCs first and then change the mode. Changing the mode while VCs are configured can produce
undesired results, and the change will not take effect until the next router reload.