Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

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0x0ff_info_1420's avatar
0x0ff_info_1420
Icon for Cirrus rankCirrus
Mar 07, 2019

Trunk / VPC Port-Channel not working properly with Nexus 9K / 2K (FEX) : Spanning-tree involved

Hello DevCentral,   I'll present to you an odd behavior using 2 Nexus 9k (9.2.1) with Nexus 2k as Fex on which two Big-IP i4600 (12.1.4) are connected.   Our Setup :   The two Big-IP are c...
application delivery
big-ip
cisco
nexus
spanning-tree
TMOS
trunk
vpc
rafaelbn's avatar
rafaelbn
Icon for Cirrostratus rankCirrostratus
Mar 07, 2019

Hello 0x0ff.info!!

 

First things first. If your BIG-IP has more than one VLAN on the TRUNK interface, you must use 'spanning-tree port type edge trunk'. That is a Cisco recommendation when the connected device is not a switch but have multiple VLANs. If it was a catalyst switch, the command would be 'spanning-tree portfast trunk'.

 

Reference

 

The idea behind portfast is to make the switch converge STP quickly on the interface, going strait to the forwarding state.

 

What I think (wild guess here) that could be happening is that since the switch is seeing dot1q tags and it's ports are configured as edge you could be hitting a bug/odd behavior on the Cisco side.