Nexus7K: HSRP with VPC setup,Shall we run BFD between HSRP peers?

booshanm · ‎04-27-2020

Reza Sharifi · ‎04-27-2020

BFD usually is not used with HSRP. It is used with routing protocols like BGP to lower the fail-over time. HSRP fail-over time is pretty fast but if you want to improve that, you can manipulate the HSRP timers.

HTH

booshanm · ‎04-27-2020

Thanks for your reply.

Here my question is will it work along with VPC?

Because VPC and HSRP are configured in a customer environment, the customer wants to configure BFD between HSRP peers.

I read in one of the CCO document that BFD with VPC is not supported. The document link mentioned,you can find it in "SVI limitation" section.

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/interfaces/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide_7x/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide_7x_chapter_0110...

SVI limitations:

Sergiu.Daniluk · ‎04-27-2020

Hi @booshanm

You do not need BFD between vPC peers. They are both active forwarding. Plus, you can enable "vpc peer-gateway" and the switches can route the traffic destined to it's peer as well.

Cheers,

Sergiu

booshanm · ‎04-27-2020

Customer want to configure the BFD on HSRP peers, not VPC peers but VPC is also running in the same box.

Sergiu.Daniluk · ‎04-27-2020

If the VLAN configured with HSRP is a vPC vlan, then HSRP will be active forwarding on both vPC peers, thus no need for BFD.

Cheers,

Sergiu

booshanm · ‎04-28-2020

As per my understanding is correct, BFD is a control plane protocol. If this a case HSRP is active /standby on the control plane and its hold on time is 10 Sec. To minimize the hello and holdon time BFD is required, right?

Sergiu.Daniluk · ‎04-28-2020

Hi @booshanm

Generally speaking yes, BFD can be configured for HSRP to improve convergence. However, since you mentioned about vPC, there are a couple of limitations which you need to be aware of. All the limitations are also mentioned in config guide:

Guidelines and Limitations for BFD

BFD has the following configuration guidelines and limitations:

if the carrier interface is a virtual port channel (vPC), BFD is not supported over the SVI interface.
When Layer 3 over vPC feature is enabled using the layer3 peer-router command, BFD enabled with echo function is not supported on a switched virtual interface (SVIs) using vPC VLANs that are part of a vPC peer-link.
vPC is not supported.

Ref: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus7000/sw/interfaces/config/cisco_nexus7000_interfaces_config_guide_8x/config-bidirectional-forwarding-detection.html

I think is pretty clear from these limitations that vPC + BFD for HSRP is not something supported.

Hope it helps,

Sergiu