06-07-2020 07:24 AM
Hello, Could you please confirm while extending EPG out where L3 gateway is out of ACI fabric, should we enable or disable the ARP flooding option, i know L2 unknown unicast and L3 unknown multicast should be set to Flood but not sure about ARP flooding.pls help.
Solved! Go to Solution.
06-07-2020 09:17 AM
Hi @Anukalp S
Before answering the question, let's discuss what happens in each scenario of the ARP flooding setting:
Now, if you have the L3 GW outside of the Fabric, you most likely have the BD in L2. In this case, what you really need to configure is ARP Flood on. If, for whatever reason, you have the BD in L3, then is debatable which option might be more suitable.
Additional note: If you have silent hosts in your network, then ARP Flooding ON is a must.
Stay safe,
Sergiu
06-07-2020 09:17 AM
Hi @Anukalp S
Before answering the question, let's discuss what happens in each scenario of the ARP flooding setting:
Now, if you have the L3 GW outside of the Fabric, you most likely have the BD in L2. In this case, what you really need to configure is ARP Flood on. If, for whatever reason, you have the BD in L3, then is debatable which option might be more suitable.
Additional note: If you have silent hosts in your network, then ARP Flooding ON is a must.
Stay safe,
Sergiu
06-07-2020 10:44 AM
Hi,Thanks for detailed information.
06-07-2020 11:10 AM - edited 06-07-2020 11:10 AM
Pleasure all mine @Anukalp S
Feel free to the community about any other questions or concerns you have!
Stay safe,
Sergiu
05-14-2023 08:12 AM - edited 05-15-2023 04:52 AM
a
08-16-2023 08:45 AM
I noticed in ACIv4 ARP Flooding is enabled by default. Is that new with ACIv4? Was always un-checked before. What is the reasoning for the change?
Thanks --dan
01-18-2024 10:42 PM
@dkmurray55,
Yes, ARP flooding is enabled by default when you create a bridge domian, thanks
01-19-2024 01:59 AM
I hate flogging a dead thread - but for the record:
In early versions of ACI, ARP flooding was DISABLED by default when you selected Optimize for the Forwarding option
In later versions - until about 5.2 (from memory - may have been 5.0) ARP flooding was both DISABLED or ENABLED by default (when you selected Optimize for the Forwarding option) depending on whether you created the BD via the right-click method or used drag-and-drop from the Tenant > Networking graphic.
From about 5.2 onwards, the default when you selected Optimize for the Forwarding option has been to enable ARP flooding
In other words, Cisco has NO IDEA what Optimize means when it come to ARP flooding!!!! This has bugged me for some time. See my previous rants at https://community.cisco.com/t5/application-centric-infrastructure/why-the-change-of-heart-re-quot-optimized-quot-forwarding-to/m-p/4032264/highlight/true#M7831 and https://community.cisco.com/t5/application-centric-infrastructure/discussion-cisco-aci-ui-inconsistencies-please-contribute/m-p/4460787/highlight/true#M11070
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