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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 8 Configuring ATM Permanent Virtual Circuit Autoprovisioning
Variable Bit Rate Non-Real Time Oversubscription
The following configuration enables the oversubscription feature and configures the interface with
an over-subscription-factor of 50.
Router(config)# interface atm 4/0/0
Router(config-if)# atm over-subscription-factor 50
Router(config-if)# exit
• To prevent oversubscription of the interface, use the no atm oversubscribe command. For example,
the following configuration disables oversubscription of the ATM 4/0/0 interface. The previously
configured factor 50 is configured on the interface, but the router does not allow the
oversubscription.
Router(config)# interface atm 4/0/0
Router(config-if)# no atm oversubscribe
Router(config-if)# exit
• It is recommended that the atm over-subscription-factor command be applied to all ports of an
ATM line card. This command controls the allocation of resources that are managed on a line card.
Enabling oversubscription on one port alone could result in other ports taking up more resources
than they were supposed to use. This could result in starving other ports for resources, which could
cause VC creation to fail.
• In atm pxf queuing mode, the number of active VCs the ATM line cards support for Cisco IOS
Release 12.3(7)XI2 or later releases is shown in
Table 8-2.
You can configure the maximum number of VCs across the ports in any fashion, provided that you
do not exceed the per-port maximum.
Although the maximum number of VBR, CBR, and shaped UBR VCs per E3/DS3 and OC-3 ATM
line card is 28,672 VCs, the router supports a maximum of 22,204 VBR, CBR, and shaped UBR VCs
per line card that you can place within virtual path (VP) tunnels. If you attempt to bring up more
than 22,204 VCs in a configuration that includes VP tunnels and VCs (hierarchical traffic shaping
configuration), the VCs might not assign traffic correctly or the VCs might not come up at all. Be
sure to limit the number of configured VBR, CBR, and shaped UBR VCs on an ATM card to less
than 22,204 VCs if you place the VCs in VP tunnels.
For the OC-12 ATM line card, the router supports 16,384 VCs in VP tunnels.
Ta b l e 8-2 Active VCs on ATM Line Cards
Line Card Max. VCs per Port Maximum VCs per Module No. VBR, CBR, Shaped UBR VCs
E3/DS3 4,096 32,768
1
1. For 32,768 VCs per module, 4096 of them must be unshaped UBR VCs.
28,672
2
2. For 28,672 VBR, CBR, and shaped UBR VCs, no VCs can be in shaped VP tunnels. If VCs are in shaped VPs, the number of VBR, CBR, and shaped
UBR VCs is 22,204.
OC-3 8,191 32,764
3
3. For 32,764 VCs per module, 4096 of them must be unshaped UBR VCs.
28,672
4
4. For 28,672 VBR, CBR, and shaped UBR VCs, no VCs can be in shaped VP tunnels. If VCs are in shaped VPs, the number of VBR, CBR, and shaped
UBR VCs is 22,204.
OC-12 16,384 (previously 14,436) 16,384 16,384
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