Specifications

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Default Route Preference Values :
How Route Is Learned Default Preference
Directly connected network 0
Static 5
MPLS 7
OSPF internal route 10
IS-IS Level 1 internal route 15
IS-IS Level 2 internal route 18
Redirects 30
RIP 100
Point-to-point interface 110
Generated or aggregate 130
OSPF AS external routes 150
IS-IS Level 1 external route 160
IS-IS Level 2 external route 165
BGP 170
3.1.3 Junos Routing Protocols
The JUNOS software implements full IP routing functionality, providing support
for IP Version 4 (IPv4). The routing protocols are fully interoperable with existing
IP routing protocols, and they have been developed to provide the scale and
control necessary for the Internet core.
The software provides the following routing and traffic engineering protocols:
3.1.3.1 Unicast routing protocols
§ IS-IS—Intermediate System-to-Intermediate System is an interior
gateway (IGP) link-state routing protocol for IP networks that uses the
shortest-path-first (SPF) algorithm, which also is referred to as the
Dijkstra algorithm, to determine routes. The JUNOS IS-IS software is a
new and complete implementation of the protocol, one in which
considerable attention has been given to issues of scale, convergence,
and resilience.
§ OSPF—Open Shortest Path First, Version 2, is an IGP that was
developed for IP networks by the Internet Engineering Task Force
(IETF). OSPF is a link-state protocol that makes routing decisions based
on the SPF algorithm. The JUNOS OSPF software is a new and
complete implementation of the protocol, one in which considerable
attention has been given to issues of scale, convergence, and resilience.
§ RIP—Routing Information Protocol, Version 2, is an IGP for IP networks
based on the Bellman-Ford algorithm. RIP is a distance-vector protocol.
RIP dynamically routes packets between a subscriber and a service
provider without the subscriber having to configure BGP or to participate
in the service provider’s IGP discovery process.
§ ICMP—Internet Control Message Protocol router discovery allows hosts
to discover the addresses of operational routers on the subnet.
§ BGP—Border Gateway Protocol, Version 4, is an exterior gateway
protocol (EGP) that guarantees loop-free exchange of routing
information between routing domains (also called autonomous systems).
BGP, in conjunction with JUNOS routing policy, provides a system of
administrative checks and balances that can be used to implement
peering and transit agreements.
3.1.3.2 Multicast routing protocols
§ DVMRP—Distance Vector Multicast Routing Protocol is a dense-mode
(flood-and-prune) multicast routing protocol.