Issue

brctl showstp shows ports that are admin up/carrier down as blocking:

[email protected]$ sudo brctl show bridge
bridge  name bridge id     STP enabled  interfaces
bridge  8000.c45444bcfc8a  yes          swp1

[email protected]$ ip l sh swp1
28: swp1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast master bridge state DOWN mode DEFAULT qlen 500 
link/ether c4:54:44:bc:fc:8a brd ff:ff:ff:ff:ff:ff

 [email protected]$ sudo brctl showstp bridge
 ... 
 swp1 (1)
 port id 8001 state blocking
 ...

Environment

• Cumulus Linux, all versions

Resolution

Use mstpctl showportdetail BRIDGE PORT, which more accurately reflects the port state as Disabled/discarding.

[email protected]$ sudo mstpctl showportdetail bridge swp1
 bridge:swp1 
 CIST info enabled no role Disabled
 port id 8.001 state discarding
 ...