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Cisco Bug: CSCvt13079 - Unable to disable unknown multicast blocking on switchport

Last Modified

Jul 30, 2020

Products (12)

  • Cisco Nexus 5000 Series Switches
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 5624Q Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 5672UP Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5696Q Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 56128P Switch
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Known Affected Releases

7.3(2)N1(1) 7.3(5)N1(1) 7.3(6)N1(1)

Description (partial)

Symptom:
Unknown multicast blocking is enabled by default on all switchports:
F340.12.01-Nexus5000-7# sh int e1/1 sw
Name: Ethernet1/1
  Switchport: Enabled
  Unknown unicast blocked: disabled
  Unknown multicast blocked: enabled <<<

When trying to disable it through issuing ‘no switchport block multicast’, this does not disable it and remains enabled:
F340.12.01-Nexus5000-7(config-if)# switchport block multicast 
F340.12.01-Nexus5000-7(config-if)# no switchport block multicast 
F340.12.01-Nexus5000-7(config-if)# sh int e1/1 sw
Name: Ethernet1/1
  Switchport: Enabled
  Unknown unicast blocked: disabled
  Unknown multicast blocked: enabled <<<

Conditions:
Nexus 5500 running software release 7.3(2)N1(1) or higher
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Bug Details Include

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  • Status
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