ARP Learning Issue

[netbeginner]

Dear Experts,

We are stucked with a problem with (Nexus 9K setup). Here is the setup for your reference.

1. We are having two Nexus 9K switches (Primary & Secondary). running with vPC ( on Port Channel-1).

2. We have created a VLAN (say Vlan 100) on switches in HSRP.

3. A server is connected from these switches and we are facing intermittent drops on the same.

While checking we came to know that ARP of the particular server is varying and sometime learning on switches respective interface (on which server is connected) and sometime on vPC.

Nexus-P# sh mac address-table address d4ae.52d0.816a
Legend:
        * - primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC
        age - seconds since last seen,+ - primary entry using vPC Peer-Link,
        (T) - True, (F) - False
   VLAN     MAC Address      Type      age     Secure NTFY Ports
---------+-----------------+--------+---------+------+----+------------------
+  690     d4ae.52d0.816a   dynamic  0         F      F    vPC Peer-Link

Nexus-P# sh mac address-table address d4ae.52d0.816a
Legend:
        * - primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC
        age - seconds since last seen,+ - primary entry using vPC Peer-Link,
        (T) - True, (F) - False
   VLAN     MAC Address      Type      age     Secure NTFY Ports
---------+-----------------+--------+---------+------+----+------------------
*  690     d4ae.52d0.816a   dynamic  0         F      F    Eth1/47

Pls suggest for troubleshooting the problem .

Regards

***

[Steve Fuller]

Hi,

So if I understand correctly:

• You have two Nexus 9P with vPC, Nexus 9K primary and Nexus 9K secondary
• The server has two NICs, one connected to Nexus 9K primary and the second connected to Nexus 9K secondary.

What it would appear is that the server is sending traffic on both its NICs. This is the most likely reason you see the port on which the MAC address of the server is learnt change from the physical port (Eth1/47) to vPC peer link.

How are the switch ports on the Nexus 9K configured? Are these simply access ports or are they also configured as a vPC? If you could post the output here that would help.

Also what is the server Operating System and how is the NIC bonding/teaming configured on that server? The way the MAC address is moving it would appear to be using some form of active-active load balancing. This is fine as long as the network is configured accordingly. If you can find out from the server admin what NIC bonding/teaming mechanism they're using we should be able to determine an appropriate configuration for the network.

Regards