Specifications

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3.2.1 Static Routing
JUNOS allows routes to be created statically through configuration that point
either to real interfaces and therefore result in traffic being forwarded, or that can
point to null interfaces such that the packets are dropped. The blackhole routes
can take one of two forms: ones where ICMP Destination Unreachable
messages are sent or ones where the packets are silently discarded
3.2.2 OSPF
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.
§ Multiple OSPF routing instances
Junos provides support for configuring multiple router instances, each running its
own OSPF instance. Without this feature enabled, only one routing instantiation
for the whole router; all IP unicast routes go into the inet.0 table, mpls routes into
the mpls.0 table and iso routes go into the iso.0 table. With multiple OSPF
routing instances enabled, each routing instance consists of a set of routing
tables, a set of interfaces which belong to these tables, and a set of routing
protocol parameters which control the information in these tables.
You can then define a ribgroup as a collection of ribs from different routing
instances. A ribgroup can be used by OSPF to import OSPF learnt routes to all its
constituent ribs. A route so installed carries the routing instance it was installed
from as an attribute. Export policies can select on routing instance attributes,
allowing exporting of OSPF routes learned in one instance as OSPF external into
another instance. The route selection process assumes that all of the instances
share a single address space. In other words, although different instances can
exist to control which prefixes are advertised to which other instances, the route
selection process still assumes that all of the instances together still use a single
address space.
This feature is useful to scale the network by separating the core instance from
the edge instance(s). It creates “overlay” networks whereby separate services are
routed only towards routers participating in that service.
3.2.3 IS-IS
Junos makes IP backbones capable of having IS-IS for doing IP routing. The
Juniper IS-IS implementation does not do routing for CLNP. The IS-IS
implementation is compliant with the IETF’s Integrated IS-IS specification as well
as with the de facto standard of the behavior of Cisco’s Integrated IS-IS
implementation. Some characteristics of the Junos implementation f IS-IS are
highlighted below :
§ passive interfaces - In the Junos IS-IS implementation, an interface can be
identified as passive, which results in IS-IS not actually running on that
interface but still having the interface included in Link State Packets (LSPs)
that the system generates
§ independently configurable timers - Junos allows for configuring hello, hello
time-out, LSP refresh interval, LSP retransmission interval and LSP flooding
interval. The LSP time-out interval is currently derived from the LSP refresh
interval. The CSNP interval is currently not configurable. Juniper is aware
of the difficulties of getting an implementation of an Internal Gateway
Protocol (IGP) such as IS-IS to scale in logical topologies as extreme as a
full mesh of ATM PVCs on a carriers’ backbone, which may be necessary to
create this mesh in order to scale to the bandwidths so they can grow their
network, and the resulting scaling impact on IS-IS is unfortunate. Juniper
has created a product that allows scaling of IP networks to very high
bandwidths without the loss of traffic engineering capability and without the
disadvantages of stressing IGPs. Having said that, however, Juniper also
realizes that it must be able to transition to the new technology and so may
need to be part of full-mesh networks for some time. To accommodate that,
Juniper’s IS-IS implementation includes all of the configuration knobs
needed in order to participate in a large full-mesh network.
§ specify level 1 and level 2 metrics on a per-interface basis
§ specify metrics on passive interfaces
§ multiple equal-cost load sharing paths