Seems like STP issue on Nexus 6K with HSRP.

[Saurabh Kishore]

Our Nexus 6K config

6K1:
interface Vlan24
  no shutdown
  vrf member ggn1
  no ip redirects
  ip address 192.168.24.4/28
  hsrp 24
    preempt delay reload 60
    priority 150
    ip 192.168.24.6

6k1(config)# show run | sec spanning
spanning-tree vlan 1-3967 priority 0

------
6k2:

interface Vlan24
  no shutdown
  vrf member ggn1
  no ip redirects
  ip address 192.168.24.5/28
  hsrp 24
    preempt delay reload 60
    priority 5
    ip 192.168.24.6

6K2# show run | sec spanning
spanning-tree vlan 1-3967 priority 0

----

Now while Doing a ping from a 192.168.24.x machine we get:
[root@usergate ~]# ping 192.168.24.6
PING 192.168.24.6 (192.168.24.6) 56(84) bytes of data.
64 bytes from 192.168.24.6: icmp_seq=1 ttl=255 time=42.8 ms
64 bytes from 192.168.24.6: icmp_seq=2 ttl=255 time=0.690 ms
64 bytes from 192.168.24.6: icmp_seq=3 ttl=255 time=41.3 ms
64 bytes from 192.168.24.6: icmp_seq=4 ttl=255 time=0.695 ms
64 bytes from 192.168.24.6: icmp_seq=5 ttl=255 time=41.6 ms
64 bytes from 192.168.24.6: icmp_seq=6 ttl=255 time=0.722 ms
64 bytes from 192.168.24.6: icmp_seq=7 ttl=255 time=37.3 ms
64 bytes from 192.168.24.6: icmp_seq=8 ttl=255 time=0.705 ms

Why does my Ping has inconsistent times?

---

All HSRP are active on Nexus 6K1

When I do a traceroute to the HSRP IP of Vlan 108  from a machine in another vlan we get:

[root@usergate ~]# traceroute 192.168.108.1
traceroute to 192.168.108.1 (192.168.108.1), 30 hops max, 60 byte packets
 1  192.168.108.40 (192.168.108.40)  3.649 ms 192.168.24.4 (192.168.24.4)  0.478 ms 192.168.108.40 (192.168.108.40)  3.848 ms
 
[root@usergate ~]# traceroute 192.168.108.1
traceroute to 192.168.108.1 (192.168.108.1), 30 hops max, 60 byte packets
 1  192.168.108.40 (192.168.108.40)  2.725 ms 192.168.24.4 (192.168.24.4)  0.449 ms 192.168.108.40 (192.168.108.40)  2.854 ms

[root@usergate ~]# traceroute 192.168.108.1
traceroute to 192.168.108.1 (192.168.108.1), 30 hops max, 60 byte packets
 1  192.168.108.40 (192.168.108.40)  3.675 ms  3.835 ms  4.016 ms

[root@usergate ~]# traceroute 192.168.108.1
traceroute to 192.168.108.1 (192.168.108.1), 30 hops max, 60 byte packets
 1  192.168.108.40 (192.168.108.40)  2.905 ms 192.168.24.4 (192.168.24.4)  0.586 ms  1.076 ms

[Florian Holzapfel]

Hi,

with this output i have to ask my magic 8 ball. sorry.

but if you use vPC why don't you use glbp (don't forget NXOS5.2 and lower GLBP do not support IPV6). My magic 8 ball means that you could maybe have  a problem that you forwarding traffic over your vPC-Peerlink.

But i don't know your design or from where do your icmp-request +-reply starts / end. but it seems layer3 (udp33434) has the problem, too.

regards,

flo

[Saurabh Kishore]

Just found out that with VPC Peer running it is mandate to have STP priority 0 on both the switches.

But this inconsistent Ping on the Network is really worrying me. The reason I am troubleshooting on this is that at times for a few minutes the network becomes very latent and Ping times to even Internal Network rises and there is a huge latency problem.

CPU, memory on the nexus switches seems to be normal, Interface errors on a few interfaces, but I really cannot nail down the problem to anything specific then I came across this behavior.

[Reza Sharifi]

Even with VPC you still need to define which switch is the root and which one is backup root.

for example: if you want switch 1 to be the primary root for MST instance 1 then you need this command:

spanning-tree mst 1 root primary

and switch 2 secondary

spanning-tree mst 1 root secondary

HTH

[Saurabh Kishore]

My spanning Tree configuration on both the switches is:

spanning-tree mode rapid-pvst
spanning-tree pathcost method short
no spanning-tree port type edge default
no spanning-tree port type network default
spanning-tree bridge assurance
no spanning-tree loopguard default
spanning-tree vlan 1-3967
spanning-tree vlan 1-3967 priority 0
spanning-tree vlan 1-3967 hello-time 2
spanning-tree vlan 1-3967 fex-hello-time 12
spanning-tree vlan 1-3967 forward-time 15
spanning-tree vlan 1-3967 max-age 20

What are the recommended configuration changes?