Chapter 26
| IP Routing Commands
Global Routing Configuration
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changes occur in the network, the routing table is updated, and those
changes are immediately reflected in the FIB.
The FIB is distinct from the routing table (or, Routing Information Base), which
holds all routing information received from routing peers. The forwarding
information base contains unique paths only. It does not contain any secondary
paths. A FIB entry consists of the minimum amount of information necessary to
make a forwarding decision on a particular packet. The typical components
within a forwarding information base entry are a network prefix, a router port
identifier, and next hop information.
◆
This command only displays routes which are currently accessible for
forwarding. The router must be able to directly reach the next hop, so the
VLAN interface associated with any static route entry must be up.
Example
Console#show ip route
Codes: C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default
C 127.0.0.0/8 is directly connected, lo
C 192.168.1.0/24 is directly connected, VLAN1
Console#
The RIB contains all available routes learned through directly attached
networks, and any additionally configured routes such as static routes. The
RIB contains the set of all available routes from which optimal entries are
selected for use by the Forwarding Information Base (see Command Usage
under the
command).
Console#show ip route database
Codes: C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
> - selected route, * - FIB route, p - stale info
C *> 127.0.0.0/8 is directly connected, lo0
C *> 192.168.1.0/24 is directly connected, VLAN1
Console#
In the following example, the numeric identifier following the routing table
name (0) indicates the Forwarding Information Base identifier.
Console#show ip route summary
IP routing table name is Default-IP-Routing-Table(0)
