VXLAN BGP VPN vs VPC peer link

[jay_7301]

Hi All,

I have a lab setup with 2 leafs and 2 spines and use VXLAN BGP EVPN. There is also a VPC peer link between the leaf devices. For some reason all traffic is being learnt via the peer link and not over the NVE interfaces, is there a reason for this is the peer link preferred over BGP? 

Thanks

[Sergiu.Daniluk]

Hi,

If the vlans are vpc vlans (allowed over peer link), in your case the local connected devices (orphan port connected to each switch) will always communicate over the peer-link.

Remember: vpc is a virtualization protocol which will make your two Nexus switches (vPC peers) to act as one from Layer 2 forwarding perspective.

This means, even the single homed devices connected devices (connected to only one single Nexus switch, on interfaces called orphan ports) will see the two switches as one:

If you want to forward traffic over vxlan, you either remove the vpc completely, either make the vlans non-vpc (remove them from vpc peer-link)

Regards,

Sergiu

[jay_7301]

Hi Sergiu,

Sorry are you saying only orphan ports will only use the vpc peer link? or will vpc'd attached devices also use the peer link?

Thanks

[Sergiu.Daniluk]

Hello,

There are three type of traffic:

• between orphan ports connected to each VPC peer -> this will use VPC peer-link
• between VPC connected servers -> here the forwarding will be done locally on vPC peer which received the traffic. BUM traffic will be forwarded over peer-link, but it will be dropped by the peer to avoid loop (vpc loop avoidance mechanism)
• between vpc connected server and orphan port connected -> here it depends. If the traffic arrives on VPC peer 1, and the orphan port is on VPC peer 2, then traffic will be forwarded over peer-link. If the traffic arrives on the vpc peers where the orphan port is connected AND the return traffic from orphan port destined to vpc connected devices, will be locally switched and forwarded out of vpc interface.

Let me know if the explanation is not clear and I will try to make some graphic illustrations for the above the scenarios.

Cheers,

Sergiu

[jay_7301]

This makes perfect sense, thank you for explanation.