Nexus 9k & VPC

I'm currently setting up a pair of 93108s and a pair of 9348 as top of cab switches at our core datacentre. The 9348 are to be used for the routing and the 93108's are for the servers / iSCSI traffic etc.

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Currently we have 3650's in the core so this should be a big upgrade hopefully.

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I have the keepalives running between the pair's via their management interfaces. then have a QSFP LACP connection between each 9348 and 93108.

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Picture in this link:

https://1drv.ms/u/s!AqQft0-q9td6h-V7pJ14HYMAhpE_Yg?e=85i04D

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However I'm testing the VPC config with a test server in a lab environment and whilst I have the VPC showing as up for the test server (1 port connected to each 93108), when testing shutting an interface to simulate a lost switch I lose connectivity to the server.

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Oddly if I shut the interface on the 'bottom' switch (as per the linked picture) I just lose connectivity externally, RDP sessions stay alive and an internal ping to the switch continues . however if I shut the interface on the upper switch I lose everything, the RDP session is lost etc.

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Obviously I've miss-configured it somewhere but I'm not 100% as to where I've gone wrong!

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Show VPC

(*) - local vPC is down, forwarding via vPC peer-link

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vPC domain id : 1

Peer status : peer adjacency formed ok

vPC keep-alive status : peer is alive

Configuration consistency status : success

Per-vlan consistency status : success

Type-2 consistency status : success

vPC role : primary, operational secondary

Number of vPCs configured : 1

Peer Gateway : Disabled

Dual-active excluded VLANs : -

Graceful Consistency Check : Enabled

Auto-recovery status : Disabled

Delay-restore status : Timer is off.(timeout = 30s)

Delay-restore SVI status : Timer is off.(timeout = 10s)

Operational Layer3 Peer-router : Disabled

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vPC Peer-link status

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id Port Status Active vlans

-- ---- ------ -------------------------------------------------

1 Po50 up 1,99-100,103-106,112,115,149-152,203,300-302,400-

403,410-412,450,460,600,678,800,820-821,850,900-9

01,990,999

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vPC status

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Id Port Status Consistency Reason Active vlans

-- ------------ ------ ----------- ------ ---------------

48 Po48 up success success 203

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I can post the config but there's not a lot to vpc, so I'm not really sure how I've got it wrong!