Hello Upendra

1721 comes with a default of 1 10/100FE port.. You can have additional ethernets by ordering WIC-1ENET module.. these WIC cards are meant for dedicated ethernet access on Layer 3... but 1700 series routers had gone End of Sale and have been replaced with the 1800 series ISR routers.. You can speak to your local cisco reseller and get information on this.

Datasheet of WIC-1ENET:

http://cisco.com/en/US/products/hw/routers/ps221/products_data_sheet09186a0080088714.html

Hope this helps.. rate replies if found useful..

Raj