how problem solving ip address secondary for switch WS-C4507R+E

[duwijakarta]

I have a complex network that is already running, there is a condition where I need an additional IP address because the IP address is almost full, is the best solution to create a secondary IP address on the same interface or do I change the subnet? the need is with the same VLAN condition so that it is not different VLAN. thanks

[Joseph W. Doherty]

. . . if it is not good for the long term, what are the future concerns that cause it to be not good for the long term? 

Possibly, the biggest concern it being "usual", which makes it just a bit more difficult to maintain.  For example, you're here asking on there forums, basically, can this work.  Personally, I've never had an issue introducing complexity when it's pretty much the only way to accomplish a service goal, but in this case you want to do this just to avoid the work to migrate to a larger replacement subnet.

As to future problems, since doing this, I believe, is unusual, you may get to discover them.

Am I saying you will have future problems?  Not at all.  It should save you immediate migration work, and may work fine ever after.

As an aside, consider the common issue of allocation of address space.  Given you need to provide a subnet to support 15 hosts, what do you do?

Normally, you would allocate, at least, a /27, but using secondaries, why not allocate a /28 and a /30?  Or, allocate eight /30s, or four /29s, or . . . ?  Using secondaries, why not?

and if it happens in the future is there a solution?

Probably, it depends on the actual problem.

[duwijakarta]

okay thank you, today I have tried to implement the secondary ip, I experienced something that is if I only add a secondary ip to the core switch that has ospf routing on the switch, after testing ping to the secondary ip from the access switch device below it does not reply, but when I add the secondary ip to the ospf routing on the core switch, the result from the access switch below can ping the secondary ip. what I want to make sure is whether it is necessary to add the secondary ip back to the ospf routing or should the primary ip be enough, then the secondary ip should automatically enter the ospf?

[Joseph W. Doherty]

is necessary to add the secondary ip back to the ospf routing or should the primary ip be enough

That was answered earlier.

To recap:

If using OSPF network statements, you'll need to "cover" the secondary.

If using OSPF the interface command, secondaries, by default, are included.