Routers provide connectivity inside enterprises, between enterprises and the Internet, and within an Internet Service Provider (ISP)
One of the largest routers e.g. the Cisco CRS-1 or Juniper T1600 interconnects internet Service Providers (ISPs), they are used within ISPs, or may be used in very large enterprise networks. The smallest routers provide connectivity for small and home offices.
This type of router are placed at the edge of the ISP network, the are normally configured to external protocol like BGP (Border gateway protocol) to another BGP of other ISP or large organisation.
Subscriber Edge Router
This type of router belongs to an end user (enterprise) organization. It’s configured to broadcast External BGP to it’s provider’s AS(s)
Inter-provider Border Router
This type of router is for Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers’ ASes.
A router that resides within the middle or backbone of the LAN network rather than at its periphery. In some instances , a core router provides a stepdown backbone , interconnecting the distribution routers from multiple building of a campus ( LAN), or Large enterprise Location (WAN). They tend to be optimized for a high brandwidth.
Wired and Wireless Routers.
Home and small office networking is becoming popular by day by the use of IP wired and wireless router.Wired and wireless router are able to maintain routing and configuration information in their routing table. They also provide the service of filtering traffic of incoming and outgoing packets based on IP addresses.
Some wireless routers combines the functions of router with those of a network switch and that of a firewall in one.