R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide

2
• Destination—IP address of the destination host or network.
• Mask—Mask length of the IP address.
• Pre—Preference of the route. Among routes to the same destination, the one with the highest
preference is optimal.
• Cost—When multiple routes to a destination have the same preference, the one with the smallest
cost becomes the optimal route.
• NextHop—Next hop.
• Interface—Output interface.
Dynamic routing protocols
Dynamic routing protocols dynamically collect and report reachability information to adapt to topology
changes. They are suitable for large networks.
Compared with static routing, dynamic routing protocols require more resources, and are complicated to
configure.
Dynamic routing protocols can be classified by different criteria, as shown in Table 2:
Table 2 Categories of
dynamic routing protocols
Criterion Categories
Optional scope
• Interior gateway protocols (IGPs)—Work within an autonomous system (AS).
Examples include RIP, OSPF, and IS-IS.
• Exterior gateway protocols (EGPs)—Work between ASs. The most popular one is
BGP.
Routing algorithm
• Distance-vector protocols—RIP and BGP. BGP is also considered a path-vector
protocol.
• Link-state protocols—OSPF and IS-IS.
Destination address
type
• Unicast routing protocols—RIP, OSPF, BGP, and IS-IS.
• Multicast routing protocols—PIM-SM and PIM-DM (For more information, see IP
Multicast Configuration Guide).
IP version
• IPv4 routing protocols—RIP, OSPF, BGP, and IS-IS.
• IPv6 routing protocols—RIPng, OSPFv3, IPv6 BGP, and IPv6 IS-IS.
NOTE:
A
n AS refers to a group of routers that use the same routing policy and work under the same
administration.
Route preference
Routing protocols (including static and direct routing) each by default have a preference. If they find
multiple routes to the same destination, the router selects the route with the highest preference as the
optimal route.
The preference of a direct route is always 0 and cannot be changed. You can configure a preference for
each static route and each dynamic routing protocol as required. The following table lists the route types
and their default preferences. The smaller the value, the higher the preference.