Hello Maksym
So from my understanding, your topology, as well as your HSRP configuration, are working fine. There are no state changes in your HSRP configuration. When you say that the “mtu 9216” and “no shutdown” commands would appear and disappear, where do you see that? In the configuration of the VLAN interface itself? So when you do a show run interface vlan 100 one time, you see these commands, and the next time you don’t? Please clarify, or give us some output of your show commands to confirm.
For your second question…
HSRP and vPC do two different things.
vPC allows you to interconnect two Nexus switches making them appear as a single logical node to other devices. vPC essentially doubles the available bandwidth (by simply adding a second device through which traffic can pass) while maintaining a layer 2 loop-free topology (no STP needs to function). So vPC primarily scales up the size of the Layer 2 network.
HSRP however, is a gateway redundancy protocol, meaning it operates on L3.
Now having said that, HSRP and vPC do work well together. When configured together, you have the following advantages:
- HSRP operates in an active/active arrangement. That means that both devices forward traffic (unlike HSRP on an IOS device). They actually perform gateway load balancing much like GLBP on IOS.
- vPC will help “tune” HSRP so that is why Cisco recommends configuring HSRP with the default settings when using vPC. In a regular HSRP configuration, you as the administrator will tune the timers to enable fast failover. When used with vPC, it is vPC that will handle the failover.
I hope this has been helpful!
Laz