secondary address on interface

[Gwiz00]

Hello,

Can someone please explain what is the purpose of a secondary address on an interface of a cisco router. How it works and why do you use it?

Thank you

 

[ADB100]

It is really a 'workaround' that should only be used if you face the particular problem it is used to fix. If you are building a network from scratch there is no need to even think about using secondary addresses. There are also implications with routing protocols when using secondary addressing. DHCP doesn't work well in these environments as well

Secondary addresses are used when you need to have two or more IP networks/subnets on the same physical network segment (Layer-2 domain). For example you initially deploy a /24 network/subnet and run out of IP addresses. You could introduce another IP network/subnet and route between the original one and this new one, or you could just add a secondary IP address to your current router.

http://www.cisco.com/en/US/products...erence_chapter09186a0080087387.html#wp1017863

I would steer clear if I were you.

HTH

Andy