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Cisco Bug: CSCvv21840 - SRGB label block in static label range incorrectly classified as dynamic label range

Last Modified

Oct 06, 2020

Products (14)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco Network Convergence System 55A2-MOD-HD-S
  • Cisco Network Convergence System 5504
  • Cisco Network Convergence System 5516
  • Cisco Network Convergence System 5502-SE
  • Cisco Network Convergence System 5508
  • Cisco Network Convergence System 5502
  • Cisco IOS XR Software
  • Cisco Network Convergence System 55A1-24H
  • Cisco Network Convergence System 55A2-MOD-S
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Known Affected Releases

6.6.3.BASE

Description (partial)

New defect

Symptom:
As per label range configuration,  all the SRGB label blocks installed by Service-Layer are in the static label range.However due to a logic error in label block delete code path, a SRGB block in the static label range can be incorrectly classified as being in the dynamic label range. This resulted in SRGB label blocks being classified as dynamic instead of static. This incorrect classification leads to many labels not being removed from the label database AVL tree correctly.Subsequent label block allocation requests failed due to conflict with existing labels for those SRGB blocks.


++++++++++ show mpls label range [17:31:37.677 UTC Thu Jul 30 2020] +++++++++++
 
Range for dynamic labels: Min/Max: 34000/749999
Range for static labels: Min/Max: 34000/99999.   <<<< Static Label Range
 
SRGB {start_label=34000, size=15000}    <<<<< Correctly classified as being in static label range
 
SRGB {start_label=49000, size=15000}     <<<<< Incorrectly classified as being in dynamic label range
 
SRGB {start_label=64000, size=15000}     <<<<< Incorrectly classified as being in dynamic label range
 
SRGB {start_label=79000, size=15000}    <<<<< Incorrectly classified as being in dynamic label range
 
SRGB {start_label=94000, size=5999}      <<<<< Incorrectly classified as being in dynamic label range

++ show mpls label table detail private location 0/RP0/CPU0 [23:26:12.940 UTC Mon Jul 27 2020] +++

Table Label   Owner                           State  Rewrite
----- ------- ------------------------------- ------ -------
0     0       LSD(A)                          InUse  Yes
0     1       LSD(A)                          InUse  Yes
0     2       LSD(A)                          InUse  Yes
0     13      LSD(A)                          InUse  Yes
0     16000   ISIS(A):1                       InUse  No
  (Lbl-blk SRGB, vers:0, (start_label=16000, size=8000)
0     24000   LSD(A)                          InUse  No
              Static(A):Service-layer         InUse  No
  (Lbl-Blk CBF, vers:0, (start_label=24000, size=10000, owner=swanagent)
0     34000   Static(A):Service-layer         InUse  No
  (Lbl-blk SRGB, vers:0, (start_label=34000, size=15000)
0     100000  ISIS(A):1                       InUse  Yes
  (SR Adj Segment IPv4, vers:0, index=1, type=0, intf=BE4, nh=104.44.7.166)
0     100001  ISIS(A):1                       InUse  Yes

Conditions:
The trigger for this issue is the label block delete request sent to LSD. The combination of label range configuration and SRGB block installed determines if the issue will be encountered or not. Only SRGB and SRLB label blocks are affected by this issue
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