HP has two different types of router to choice from:
Modular Ethernet RoutersThese routers have expansion slots so customer can deploy additional ports option now or in the future.
A6600 Router Series | A7000 dl Router Series | A8800 Router Series | A-MSR50 Series
Fixed Port Ethernet RoutersThese routers come with a fixed amount of ports and cannot be upgraded.
A-MSR20 Series | A-MSR20-1x Series | A-MSR30 Series | A-MSR900 Series