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VDX Spanning Tree with VCS and Cisco Config Check


I have two VDX 6740 switches I inherited when I started here. They have VCS configured between them. I'm not exactly sure how VCS works with Spanning Tree but I assume Spanning-tree doesn't need to happen over the VCS enable links. Right? The person who originally set these up did not enable spanning-tree according to "show spanning-tree" so I cannot see what spanning-tree looks like on these two vcs links.

But I need to connect these two up to a Cisco Switch that will be running spanning-tree, RSTP to be exact. I've been looking through docs, but I think I have this correct. Does this look right? Seems straightforward except the spanning-tree bpdu mac. That is kinda funny. The two links in the config are not the VCS links. They are some extra 40G ports I have.

# Enable RSTP
protocol spanning-tree rstp
exit

# Setup Interfaces
interface FortyGigabitEthernet 1/0/49
description Cisco-Switch
switchport
switchport mode trunk
spanning-tree bpdu-mac 0100.0ccc.cccd
no shutdown[/code]interface FortyGigabitEthernet 1/0/49
description Cisco-Switch
switchport
switchport mode trunk
spanning-tree bpdu-mac 0100.0ccc.cccd
no shutdown[/code]
Sorry for the kind of newb question. I don't normally need to administer these switches, they are some oddball corner ones used for storage traffic and I don't have any ones to test on.

2 replies

Userlevel 7
Hi,

the BPDU MAC address is that used by Cisco's Per VLAN Spanning Tree. The name RSTP usually means the proprietary Rapid-PVST+ with Cisco. Depending on the port configuration Cisco will send different BPDUs, some to the standard BPDU destination MAC, some to the Cisco PVST+ MAC.

I cannot tell you the exact configuration you need for your network, because it depends on quite a few details.

I have tested Rapid-PVST+ compatibility between ExtremeXOS and Cisco IOS, and documented that at https://www.unix-ag.uni-kl.de/~auerswal/exos-cisco-rapid-pvstp/. That might help you understand what you need in your network.

Thanks,
Erik
Userlevel 1
Hi Keith,

That is correct that ISL links between nodes in VCS cluster should not have spanning-tree configured, VCS cluster has his own loop prevention mechanism

Best Regards,
Yulia

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