AIS AI2524 Manuel D’Utilisation
Chapter 9: AI2524 OSI/CLNP Configuration Steps
August 1997
Page 9-9
2524UM
routing ISO IGRP; it can be configured to be Level 1 only, Level2
only, or both Level 1 and Leve l2 when routing IS-IS.
only, or both Level 1 and Leve l2 when routing IS-IS.
ESs communicate with ISs using the ES-IS protocol. Lev el1 and
Level 2 ISs communicate with each other using either ISO IS-IS or
Cisco's ISO IGRP protocol.
Level 2 ISs communicate with each other using either ISO IS-IS or
Cisco's ISO IGRP protocol.
Static Routing
Static routing is used when it is not possible or desirable to use dy-
namic routing. Here are some instances of when you would use static
routing:
namic routing. Here are some instances of when you would use static
routing:
z
If your network includes WAN links that involve paying for con-
nect time or for per-packet charges, use static routing, rather than
paying to run a routing protocol and all its routing update packets
over that link.
nect time or for per-packet charges, use static routing, rather than
paying to run a routing protocol and all its routing update packets
over that link.
z
If you want routers to advertise connectivity to external networks,
but you are not running an interd o mainrouting protocol, you must
use static routes.
but you are not running an interd o mainrouting protocol, you must
use static routes.
z
If you must interoperate with another vendor's equipment that
does not support any of the dynamic routing protocols that Cisco
supports, you must use static routing.
does not support any of the dynamic routing protocols that Cisco
supports, you must use static routing.
z
For operation over X.25, Frame Relay, or SMDS networks, static
routing is generally preferable.
routing is generally preferable.
Warning: An interface that is configured for static routing cannot
reroute around failed links.
Routing Decisions
A CLNP packet sent to any of the defined NSAP addresses or NETs
will be received by the router. The Cisco IOS software uses this algo-
rithm to select which NET to use when it sends a packet:
will be received by the router. The Cisco IOS software uses this algo-
rithm to select which NET to use when it sends a packet:
z
If no dynamic routing protocol is running, use the NET defined for
the outgoing interface, if it exists; otherwise, use the NET defined
for the router.
the outgoing interface, if it exists; otherwise, use the NET defined
for the router.
z
If ISO IGRP is running, use the NET of the ISO IGRP routing pro-
cess that is running on the interface.
cess that is running on the interface.
z
If IS-IS is running, use the NET of the IS-IS routing process that
is running on the interface.
is running on the interface.