A
group of routers that are exchanging routing information through a
common routing protocol. A single AS can represent many IP networks.
Dynamic routes
IP
layer routing table entries that are dynamically managed and can automatically
change in response to network topology changes. For IPv4, these routes
are managed by a routing daemon. For IPv6, these routes can be managed
by a routing daemon, and they can also be learned by listening to
router advertisement messages received from routers as part of the
router discovery protocol.
Exterior Gateway Protocol (EGP)
A
routing protocol that is spoken by routers that belong to different
autonomous systems when those routers are configured to share routing
information between autonomous systems. This topic does not discuss
exterior gateway routing.
Interior Gateway Protocol (IGP)
A routing protocol that is spoken by routers that belong to the
same autonomous system. Each AS has a single IGP. A separate AS within
a network can be running a different IGP.
Main route table
An
IPv4 or IPv6 route table that is populated by using static routes
and dynamic routes. These route tables have the name EZBMAIN. A TCP/IP
stack has one main IPv4 route table and one main IPv6 route table.
When policy-based routing is not in use, the main route tables contain
all of the routes that a TCP/IP stack uses when it is making routing
decisions. When policy-based routing is in use, policies can be configured
to use the main route tables in routing decisions when no route is
found in a policy-based route table.
Policy-based route table
A
route table that is configured for use by policy-based routing. A
TCP/IP stack can have zero or more policy-based route tables. A policy-based
route table can be defined by using a flat file that is parsed by
the Policy Agent, or by using the IBM® Configuration
Assistant for z/OS® Communications
Server. A policy-based route table definition can contain static routes,
dynamic routing parameters for controlling the scope of dynamic routes
that are added to the table, or both. Policy rules and actions can
then be defined to indicate, for given types of traffic, which route
tables the TCP/IP stack is to use when it is making routing decisions.
Policy-based routing (PBR)
A
technique that is used to make routing decisions that are based on
policies that are defined by the network administrator. Policy-based
routing selects a route for outbound traffic from a set of policy-based
route tables, and optionally the main route table, according to the
policy defined for the traffic.
Replaceable static routes
IPv4 static routes that can be replaced by OMPROUTE, or IPv6 static
routes that can be replaced by OMPROUTE or by routes that are learned
by listening to router advertisement messages received from routers
as part of the router discovery protocol.
Router
A
device or host that interprets protocols at the IP layer and forwards
datagrams on a path towards their correct destination.
Routing
The process that is used in an IP network to deliver a datagram
to the correct destination.
Routing daemon
A
server process that manages the IP route table.
Static routes
IP
layer routing table entries that are manually configured (by using
the BEGINROUTES or GATEWAY configuration statements) and do not change
automatically in response to network topology changes, except when:
The change is due to an ICMP redirect (if not disabled).
A dynamic routing protocol learns a route to a destination configured
as a replaceable static route.