Secondary IP Addresses

[F Martinez]

Hello,

What are the reasons why we would use secondary IP addresses?

Thank you in advance!

[Hector Gustavo Serrano Gutierrez · Accepted solution]

One of the reasons I can think is to be used as a workaround when you have no more Layer 3 ports available in your Router and you have a need to configure a new subnet.

The secondary IP address can be used as a default gateway for the new subnet.

However, the negative outcome is that you will have 2 different subnets on the same broadcast domain.

It is always a best practice to have 1 subnet per broadcast domain.

Let's say that in this case, you had to use the secondary IP address as a workaround due to the lack of ports in your Router.

I hope this helps.

Best Regards.

[Joseph W. Doherty]

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Posting

One common usage is when you want to migrate hosts from one subnet to another, such as changing the subnet's size.

BTW, by default, Cisco secondaries hosts will not be able to obtain a DHCP IP.