Nexus ARP Broadcast issue

isaac-boateng — Sun, 02 Mar 2025 04:27:47 GMT

We have ESXI host with four NIC cards each, two of the NICs are connected to our Nexus N9K-C93180YC-FX3-01 and the other two are connected to N9K-C93180YC-FX3-02 operating in Layer 2 mode. The interface configuration on these interfaces is just switchport mode trunk to the ESXI host.

For some reason host connected to Nexus-2 on the same VLAN are not able to ping from Host connected to Nexus-1 but able to ping anything else outside its VLAN but the reverse works when Host on Nexus-2 are able to ping host on Nexus-1.

I have tested this by creating SVIs on both Nexus to test. What I realized is that when I ping from Nexus-1 SVI to host connected on Nexus-2, I am able to ping some of the VMs and not some. Below is my VPC configuration. Can anybody tell me what is going on here.

Nexus-1

================

vpc domain 2
role priority 20
peer-keepalive destination 1.1.1.2 source 1.1.1.1 vrf keepalive
delay restore 150
peer-gateway
layer3 peer-router
ip arp synchronize
vpc peer-link

Nexus-2

======================

vpc domain 2
role priority 30
peer-keepalive destination 1.1.1.1 source 1.1.1.2 vrf keepalive
delay restore 150
peer-gateway
layer3 peer-router
ip arp synchronize
vpc peer-link

Re: Nexus ARP Broadcast issue

M02@rt37 — Sun, 02 Mar 2025 08:34:13 GMT

Hello @isaac-boateng

Please share these commands' output:

#show vpc

#show vpc consistency-parameters

Re: Nexus ARP Broadcast issue

paul driver — Sun, 02 Mar 2025 12:49:52 GMT

Hello
as you have vPC I would have expected for the links on the exsi host to be aggregated /teamed

Re: Nexus ARP Broadcast issue

isaac-boateng — Mon, 03 Mar 2025 03:36:46 GMT

Nexus-01

=================================

show vpc
Legend:
(*) - local vPC is down, forwarding via vPC peer-link

vPC domain id : 2
Peer status : peer adjacency formed ok
vPC keep-alive status : peer is alive
Configuration consistency status : success
Per-vlan consistency status : success
Type-2 consistency status : success
vPC role : primary, operational secondary
Number of vPCs configured : 14
Peer Gateway : Enabled
Dual-active excluded VLANs : -
Graceful Consistency Check : Enabled
Auto-recovery status : Disabled
Delay-restore status : Timer is off.(timeout = 150s)
Delay-restore SVI status : Timer is off.(timeout = 10s)
Delay-restore Orphan-port status : Timer is off.(timeout = 0s)
Operational Layer3 Peer-router : Enabled
Virtual-peerlink mode : Disabled

vPC Peer-link status
---------------------------------------------------------------------
id Port Status Active vlans
-- ---- ------ -------------------------------------------------
1 Po11 up 1-12,16,20,24,28,32,36,40,44,48,52,60,64-70,170,
666

show vpc consistency-parameters global

Legend:
Type 1 : vPC will be suspended in case of mismatch

Name Type Local Value Peer Value
------------- ---- ---------------------- -----------------------
STP MST Simulate PVST 1 Enabled Enabled
STP Port Type, Edge 1 Normal, Disabled, Normal, Disabled,
BPDUFilter, Edge BPDUGuard Disabled Disabled
STP MST Region Name 1 "" ""
STP Disabled 1 None None
STP Mode 1 Rapid-PVST Rapid-PVST
STP Bridge Assurance 1 Enabled Enabled
STP Loopguard 1 Disabled Disabled
STP MST Region Instance to 1
VLAN Mapping
STP MST Region Revision 1 0 0
Interface-vlan admin up 2 20 20
Interface-vlan routing 2 1,20,28,36,48 1,20,28,36,48
capability
Xconnect Vlans 1
QoS (Cos) 2 ([0-7], [], [], [], ([0-7], [], [], [],
[], [], [], []) [], [], [], [])
Network QoS (MTU) 2 (1500, 1500, 1500, (1500, 1500, 1500,
1500, 1500, 1500, 1500, 1500, 1500,
1500, 1500) 1500, 1500)
Network Qos (Pause: 2 (F, F, F, F, F, F, F, (F, F, F, F, F, F, F,
T->Enabled, F->Disabled) F) F)
Input Queuing (Bandwidth) 2 (0, 0, 0, 0, 0, 0, 0, (0, 0, 0, 0, 0, 0, 0,
0) 0)
Input Queuing (Absolute 2 (F, F, F, F, F, F, F, (F, F, F, F, F, F, F,
Priority: T->Enabled, F) F)
F->Disabled)
Output Queuing (Bandwidth 2 (100, 0, 0, 0, 0, 0, (100, 0, 0, 0, 0, 0,
Remaining) 0, 0) 0, 0)
Output Queuing (Absolute 2 (F, F, F, F, F, F, F, (F, F, F, F, F, F, F,
Priority: T->Enabled, T) T)
F->Disabled)
Allowed VLANs - 1-12,16,20,24,28,32,36 1-12,16,20,24,28,32,36
,40,44,48,52,60,64-70, ,40,44,48,52,60,64-70,
170,666 170,666
Local suspended VLANs - - -

Nexus -02

=================

show vpc
Legend:
(*) - local vPC is down, forwarding via vPC peer-link

vPC domain id : 2
Peer status : peer adjacency formed ok
vPC keep-alive status : peer is alive
Configuration consistency status : success
Per-vlan consistency status : success
Type-2 consistency status : success
vPC role : secondary, operational primary
Number of vPCs configured : 14
Peer Gateway : Enabled
Dual-active excluded VLANs : -
Graceful Consistency Check : Enabled
Auto-recovery status : Disabled
Delay-restore status : Timer is off.(timeout = 150s)
Delay-restore SVI status : Timer is off.(timeout = 10s)
Delay-restore Orphan-port status : Timer is off.(timeout = 0s)
Operational Layer3 Peer-router : Enabled
Virtual-peerlink mode : Disabled

show vpc consistency-parameters global

Legend:
Type 1 : vPC will be suspended in case of mismatch

Re: Nexus ARP Broadcast issue

isaac-boateng — Fri, 07 Mar 2025 03:07:43 GMT

Issue was resolved by Reload ascii

Re: Nexus ARP Broadcast issue

M02@rt37 — Fri, 07 Mar 2025 05:55:07 GMT

Hello @isaac-boateng

Thanks for the outputs and your feedback.

Great that is ok for you now !

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