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[MX] Hierarchical-scheduler maximum-hierarchy-levels 2 required for MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE



Article ID: KB32637 KB Last Updated: 31 Jul 2020Version: 2.0

When using hierarchical-scheduler for MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE, a maximum-hierarchy-levels 2 statement is needed. 

When hierarchical-scheduler is configured without maximum-hierarchy-levels, the default is maximum-hierarchy-levels 3. MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE only supports maximum-hierarchy-levels 2. 

There is no warning on commit if you do not configure this statement.


A syslog event is logged, reporting that the card does not support more than 2 levels: 

Mar 12 10:36:05.600840 25477 rtsock_current.c:5174 rts_current_build_ifd() ERROR : DCD_PARSE_ERROR_MAX_HIER_LEVELS_2: xe-7/0/1: PIC or encapsulation type does not support more than 2 levels of scheduler hierarchy

Unexpected results may occur.  In 16.1 releases, configuring hierarchical-scheduler on MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE without maximum-hierarchy-levels 2 can cause protocols utilizing interfaces on those cards to unexpectedly reset during graceful routing switchover.  If you configure dcd traceoptions, you will see that the system deletes the ifl (interface family logical - so any vlans configured) during switchover which causes protocols to drop. This was not observed in issues prior to 16.1.   

Configure DCD traceoptions: 

set interfaces traceoptions file dcd
set interfaces traceoptions flag all

In an example case, during switchover with GRES/NSR, BGP bounced due to interface change. However, the physical interface never drops.  In the example below, hierarchical-scheduler has been configured on xe-7/0/1 with single vlan 1002. 

Mar  6 10:36:05  router_name rpd[18515]: bgp_ifachange_group:8319: NOTIFICATION sent to (External AS 200): code 6 (Cease) subcode 6 (Other Configuration Change), Reason: Interface change for the peer-group

A review of the DCD traceoptions shows that the logical interfaces were deleted and added during switchover:

[10:36:05:315.165] dcd        P    iflogical  delete  xe-7/0/1.0 flags=0xc000 idx=539, gen=352 lr=0, pifd=269, uidx=0, privf=0x0 snmpid=1595, iflsetidx=0
[10:36:05:665.834] dcd        P    iflogical  delete  xe-7/0/1.1002 flags=0xc000 idx=540, gen=353 lr=0, pifd=269, uidx=0, privf=0x0 snmpid=2198, iflsetidx=0
[10:36:05:665.883] dcd        P    iflogical  delete  xe-7/0/1.32767 flags=0x400c000 idx=541, gen=354 lr=0, pifd=269, uidx=0, privf=0x0 snmpid=2199, iflsetidx=0

Once maximum-hierarchy-levels 2 is added to xe-7/0/1 config, no further protocols drops are seen.


Hierarchical-scheduler configured on an interface on MPC of type MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE without including ​maximum-hierarchy-levels 2.  


Include ​maximum-hierarchy-levels 2  when using hierarchical-scheduler on ​MPC of type MPCE Type 3D, MPC4E 3D 32XGE, and MPC4E 3D 2CGE+8XGE. 

set interface xe-x/y/z ​hierarchical-scheduler​ maximum-hierarchy-levels 2 
Modification History:
2020-07-31: Added the related link where the limitation is mentioned.

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