network and the Internet through the distribution router only. Having a full route table on the remote router,
in this example, would serve no functional purpose because the path to the corporate network and the Internet
would always be through the distribution router. The larger route table would only reduce the amount of
memory required by the remote router. Bandwidth and memory can be conserved by summarizing and filtering
routes in the distribution router. The remote router need not receive routes that have been learned from other
networks because the remote router must send all nonlocal traffic, regardless of destination, to the distribution
router. If a true stub network is desired, the distribution router should be configured to send only a default
route to the remote router. The EIGRP Stub Routing feature does not automatically enable summarization on
the distribution router. In most cases, the network administrator needs to configure summarization on the
distribution routers.
Without the stub feature, even after the routes that are sent from the distribution router to the remote router
have been filtered or summarized, a problem might occur. If a route is lost somewhere in the corporate network,
EIGRP could send a query to the distribution router, which in turn sends a query to the remote router even if
routes are being summarized. If there is a problem communicating over the WAN link between the distribution
router and the remote router, an EIGRP stuck in active (SIA) condition could occur and cause instability
elsewhere in the network. The EIGRP Stub Routing feature allows a network administrator to prevent queries
from being sent to the remote router.
Route Policy Options for an EIGRP Process
Route policies comprise series of statements and expressions that are bracketed with the
route-policy
and
end-policy
keywords. Rather than a collection of individual commands (one for each line), the statements
within a route policy have context relative to each other. Thus, instead of each line being an individual
command, each policy or set is an independent configuration object that can be used, entered, and manipulated
as a unit.
Each line of a policy configuration is a logical subunit. At least one new line must follow the
then
,
else
,
and
end-policy
keywords. A new line must also follow the closing parenthesis of a parameter list and the
name string in a reference to an AS path set, community set, extended community set, or prefix set (in the
EIGRP context). At least one new line must precede the definition of a route policy or prefix set. A new line
must appear at the end of a logical unit of policy expression and may not appear anywhere else.
This is the command to set the EIGRP metric in a route policy:
RP/0/RP0/CPU0:router(config-rpl)#
set eigrp-metric bandwidth delay reliability loading mtu
This is the command to provide EIGRP offset list functionality in a route policy:
RP/0/RP0/CPU0:router(config-rpl)#
add eigrp-metric bandwidth delay reliability loading mtu
A route policy can be used in EIGRP only if all the statements are applicable to the particular EIGRP attach
point. The following commands accept a route policy:
•
default-information allowed
—Match statements are allowed for destination. No set statements are
allowed.
•
route-policy
—Match statements are allowed for destination, next hop, and tag. Set statements are allowed
for eigrp-metric and tag.
•
redistribute
—Match statements are allowed for destination, next hop, source-protocol, tag and route-type.
Set statements are allowed for eigrp-metric and tag.
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
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Implementing EIGRP
Route Policy Options for an EIGRP Process