Routing protocols

• RIP is a distance vector routing
• protocol used for routing within an autonomous system (i.e.an IGP).
• RIP uses the hop count as the metric.
• RIP networks are limited in size to a maximum of 15
• hops between any two networks. A network with a hop count of 16 indicates
• an unreachable network.
• RIP v1 is a classful protocol; RIP v2 is a classless
• protocol.

RIP is best suited for small private networks.

• EIGRP is a hybrid routing protocol
• developed by Cisco for routing within an AS.

• EIGRP uses a composite number for the metric that
• indicates bandwidth and delay for a link. The higher the bandwidth, the
• lower the metric.
• EIGRP is a classless protocol.

• EIGRP is best suited for medium to large private
• networks.

OSPF is a link state routing protocol used for routing within an AS.

• OSPF uses a relative link cost for the metric.
• OSPF is a classless protocol.
• OSPF divides a large network into areas.

• Each autonomous system requires an area 0 that
• identifies the network backbone.
• All areas are connected to area 0, either directly
• or indirectly through another area.
• Routes between areas must pass through area 0.

• Internal routers share routes within an area;
• area border routers share routes between areas; autonomous system
• boundary routers share routes outside of the AS.
• A router is the boundary between one area and another
• area.
• OSPF is best suited for large private networks.

IS-IS is a link state routing protocol used for routing within an AS.

• IS-IS uses a relative link cost for the metric.
• IS-IS is a classless protocol.
• The original IS-IS protocol was not used for routing IP
• packets; use Integrated IS-IS to include IP routing support.
• IS-IS divides a large network into areas. There is no
• area 0 requirement, and IS-IS provides greater flexibility than OSPF for
• creating and connecting areas.
• L1 routers share routes within an area; L2
• routers share routes between areas; an L1/L2 router can share
• routes with both L1 and L2 routers.
• A network link is the boundary between one area and
• another area.

• IS-IS is best suited for large private networks,
• supporting larger networks than OSPF. IS-IS is typically used within an ISP,
• and easily supports IPv6 routing.

BGP is an advanced distance vector protocol (also called a path vector protocol). BGP is an exterior gateway protocol (EGP) used for routing between autonomous systems.