A distribute list is a filtering mechanism for routing updates. Distribute
lists do not permit or deny the actual packets from entering the routers, only
which routing updates a router will send or receive. A distribute list calls on
an access list and checks which networks are supposed to be permitted. If the
access list does not contain the network, it will automatically be denied. A
distribute list can be applied on incoming routing updates or outgoing routing
updates.
This example shows two routers running EIGRP between each
other.
A
distribute-list in is configured, but because the access
list does not contain the permit statement for 131.108.0.0,
router R2 is not installing this route in the routing table.
Debugs
and Verification
Figure
shows
the current configuration of router R2. In the access list configuration, the
network 131.108.0.0 is not explicitly permitted (and, therefore denied), so the
router is not installing any subnets of the 131.108.0.0 network. In this case,
the access list was incorrectly configured with the wrong network, 131.107.0.0.
Solution
Figure
shows the new
configuration of router R2 with the correct access list.
Figure
shows that
router R2 is learning EIGRP routes after the configuration change.