Gratuitous ARP in Nexus 7000

[e-chuah]

We are in the process of migrating our servers from Cat6500 (HSRPv1) to Nexus 7000 (HSRPv2). The HSRP virtual ip address remains the same after the migration. During the migration, we will shut down the Layer3 interface vlan on the Cat6500 and create the new Layer 3 interface vlan on the N7K. Because we are migrating to HSRPv2, the HSRP virtual MAC address will change.  Would like to check if there is there any way for the N7K to send gratuitous ARP to all the servers so that their ARP cache are refreshed. does "ip arp gratuitous update" help ?  THanks Eng Wee

[Jayakrishna Mada]

Hi Eng Wee,

Nexus sends gratuitous arp by default. This command is enabled on the interface by default. There is nothing special that you need to do for the switch to send the gratuitous arps.

JayaKrishna

[MICHAEL TJANDRA]

hi,

Is there a way to disable gratouitous arp on Nexus N7K / N5K

Thank you.

[Vishal Pathak]

You can use the below commands to disable gratuitous arp on an interface : 

switch# configure terminal
switch(config)# interface ethernet x/y
switch(config-if)# no ip arp gratuitous request

By default gratuitous arp sending and receiving is enabled.

[sbhadrav@cisco.com]

Ip arp gratuitous: disable the ability for an SVI or router interface to send gratuitous ARP is that correct? If so, am I correct in assuming disabling gratuitous ARP using "no ip arp gratuitous" will impact the functionality of protocols such as HSRP/VRRP?
I have never done it but I think it will impact the functionally of the protocol since it will disable sending arp packets.

BTW, the command to disable it for HSRP is "no standby arp gratuitous"

I also noticed that this command is not available on all platforms.

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp_fhrp/configuration/15-sy/fhp-15-sy-book/HSRP-Gratutious-ARP.html

ip gratuitous-arp: this is specific to PPP connections. Disabling this using "no ip gratuitous-arp" will NOT impact the functionality of protocols such as HSRP/VRRP?