Cisco MGX 8800 Series Switches

Field Notice: No SVC/SPVC Can Be Routed Over PNNI VNNI (VT) Interfaces Using Different VPIs

April 15, 2005

Products Affected

  • BPX Eqipped with SES PNNI Controller

Problem Description

No SVCs or SPVCs can be routed over PNNI VNNI (VT) interfaces when ILMI is enabled, configured for auto-negotiation and using different VPIs at either end of the PVP through a Service Provider network.

The scenario is similar to this:


Where VPI1 does not equal VPI2.

This anomaly has been observed in the MGX 2.1 and 3.0 trains.


  • ILMI= Interim Local Management Interface

  • SVC= Switched Virtual Circuit

  • SPVC= Soft Permanent Virtual Circuit

  • PNNI= Private Network-Network Interface

  • PVP= Permanent Virtual Path

  • VCI= Virtual Channel Identifier

  • VNNI= Virtual Network-to-Network Interface

  • VPI= Virtual Path Identifier

  • VT= Virtual Trunk


All the conditions listed below must apply for this anomaly to occur.


  • One of the cards listed in Products Affected section must be configured as shown below.

  • VNNI/VT configured for PNNI

  • ILMI enabled

  • ILMI auto-negotiation enabled

  • Different VPIs at either end of the PVP

Problem Symptoms

SVC and SPVC connections fail with cause code #35.

This can be seen in the following line of the dspcon command output:

Last Fail Cause: requested VPCI/VCI not available.

Another symptom is that minSvccVpi is greater than maxSvccVpi and minSvpcVpi is greater than maxSvpcVpi in one end of the PNNI link. This can be seen in the output of the command dsppnport.

nodename.7.PXM.a > dsppnport 1:1.4:14 

Port: 1:1.4:14 Logical ID: 16848910 
IF status: up Admin Status: up 
UCSM: enable SVC Routing Pri: 8 
Auto-config: enable Addrs-reg: enable 
IF-side: network IF-type: nni 
UniType: private Version: pnni10 
PassAlongCapab: n/a 
Input filter: 0 Output filter: 0 
minSvccVpi: 11 maxSvccVpi: 10 <===== 
minSvccVci: 35 maxSvccVci: 65535 
minSvpcVpi: 11 maxSvpcVpi: 10 <===== 

In some scenarios, connections do not route over this PNNI interface failing with a cause No. 35,

"requested VPCI/VCI not available" 
Last Fail Cause: requested VPCI/VCI not available


A workaround is to disable ILMI auto-configuration using the command cnfautocnf. With auto-configuration disabled, the ILMI slave does not start ATM layer parameter negotiation while ports come up. Instead, the ILMI slave uses the local configuration parameters. The default state for auto-configuration is enabled.

Cisco recommends that network administrators disable ILMI auto-negotiation on all Virtual Trunks. This feature should be left disabled until the network is upgraded to a release of MGX 3.0 that contains the fix for this anomaly.

The solution to this anomaly will be applied to Releases in the 3.0 train. It is expected to be included in the MGX 3.0.23 as well as the soon to be released MGX 4.0 software.


To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.



CSCea08808 (registered customers only)

ILMI advertizing incorrect values for Virtual Trunks. (This bug applies to BPX.)

CSCdz87147 (registered customers only)

SVC/SPVC not route over PNNI VNNI (VT) intf using different VPIs (This bug applies to MGX8800.)

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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