H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – IP Routing Overview
H3C S7500E Series Ethernet Switches Chapter 1 IP Routing Overvie
w
1-4
I. Operational scope
z Interior gateway protocols (IGPs): Work within an autonomous system, including
RIP, OSPF, and IS-IS.
z Exterior gateway protocols (EGPs): Work between autonomous systems. The
most popular one is BGP.
 Note:
An autonomous system refers to a group of routers that share the same routing policy
and work under the same administration.
II. Routing algorithm
z Distance-vector protocols: RIP and BGP. BGP is also considered a path-vector
protocol.
z Link-state protocols: OSPF and IS-IS.
The main differences between the above two types of routing algorithms lie in the way
routes are discovered and calculated.
III. Type of the destination address
z Unicast routing protocols: RIP, OSPF, BGP, and IS-IS.
z Multicast routing protocols: PIM-SM and PIM-DM.
This chapter focuses on unicast routing protocols. For information on multicast routing
protocols, refer to the Multicast Protocol Configuration.
IV. Version of IP protocol
IPv4 routing protocols: RIP, OSPFv2, BGP4 and IS-IS.
IPv6 routing protocols: RIPng, OSPFv3, IPv6 BGP, and IPv6 IS-IS.
1.2.3 Routing Protocols and Routing Priority
Different routing protocols may find different routes to the same destination. However,
not all of those routes are optimal. In fact, at a particular moment, only one protocol can
uniquely determine the current optimal routing to the destination. For the purpose of
route selection, each routing protocol (including static routes) is assigned a priority. The
route found by the routing protocol with the highest priority is preferred.
The following table lists some routing protocols and the default priorities for routes
found by them: