Usha -
When defining filter rules in a template, the probes' execute a logical AND of all defined filter rules. If you wish to use a custom alarm for a subset of interfaces and a another default alarm for the rest of the interfaces, you would be better off defining a "Component User Defined Property 1" for each of the interfaces that you want to use a custom alarm (like "customAlarm") then change the filter in your template for the interface component to
ifAdminStatus => [Condition="Equals", Value=1]
ifOperStatus => [Condition="Equals", Value=1]
Component User Defined Property 1 => [Condition="Not Equals", Value="customAlarm"]
You can then manually configure the small number of interfaces that you want to raise a custom alarm for, or created a second template with a filter that would allow the template to be applied to this subset of alarms with the customer alarm defined in the template.