The difference is that modular access routers give you more flexibility to expand your router in various ways to suit your network needs by way of having a different and wide variety of modules. Integrated service routers or ISRs do the same thing by optimizing themselves for secure and concurrent transfer of data, voice and images at wire-speed. They provide flexibility on service (security, unified communications, data, wireless, etc.) that you can offer to your users.

The difference is that modular access routers give you more flexibility to expand your router in various ways to suit your network needs by way of having a different and wide variety of modules. Integrated service routers or ISRs do the same thing by optimizing themselves for secure and concurrent transfer of data, voice and images at wire-speed. They provide flexibility on service (security, unified communications, data, wireless, etc.) that you can offer to your users.