Comparing OSPF and EIGRP Logic to BGP

Comparing OSPF and EIGRP Logic to BGP

• OSPF/EIGRP. Forms neighbor relationship before sending routing information. 
• BGP. Same

• OSPF/EIGRP Neighbors typically discovered using multicast packets on the connected subnets.
• BGP. Neighbor IP address is explicitly conigured and may not be on common subnet.

• OSPF/EIGRP. Does not use TCP.
• BGP. Uses a TCP connection between neighbors (port 179)

• OSPF/EIGRP. Advertises prefix/length
• BGP. Advertises prefix/lenght, called Network Layer Reachabilitiy Information (NLRI)

• OSPF/EIGRP.Advertises metric information 
• BGP. Advertises a variety of path attributes (PA) that BGP uses instead of a metric to choose the best path.

•  OSPF/EIGRP Emphasis on fast convergence to the truly most efficient route
• BGP. Emphasis on scalability: may not always choose the most efficient route.

•  OSPF/EIGRP. Link state (OSPF) or distance vector (EIGRP) logic.
• BGP. Path vector logic (similar to distance vector).

Public IP Address assignment model

Step. 1 ICANN and IANA group public IPv4 and IPv6 addresses by major geographic region.
Step. 2 IANA allocates those address ranges to Regional Internet Registries (RIR)
Setp. 3 Each RIR further subdivides the address space by allocating public address ranges to National Internet Registries (NIR) or Local Internet Registries (ISPs are typically LIRs)
Step. 4 Eacht type of Internet Registry (IR) can assign further subdivided range of addresses to the end user organization to use.