Information Technology Reference
In-Depth Information
In Example 8-2, notice that the child routes do not share the same subnet mask, as was the case in the
classful example. In this case, we are implementing a network addressing scheme with VLSM.
In the partial output of the routing table in Example 8-2, indicate whether each route is a parent route
or a child route by checking the appropriate column.
Example 8-2
Parent and Child Routes: Classless
172.16.0.0/16 is variably subnetted, 3 subnets, 3 masks
R 172.16.0.0/18 [120/1] via 10.10.10.5, 00:00:28, Serial0/0/0
C 172.16.68.0/22 is directly connected, FastEthernet0/0
C 172.16.72.0/23 is directly connected, FastEthernet0/1
Route
Parent
Child
172.16.0.0
X
172.16.0.0
X
172.16.68.0
X
172.16.72.0
X
In Table 8-2, describe each part of the partial output shown in Example 8-2.
Table 8-2
Command Output Description: Classless Routes
Command Output
Description
172.16.0.0
Classful parent route
/16
Classful mask
is variably subnetted,
Child routes have different masks
3 subnets, 3 masks
Number of subnets and masks for this parent route
R
Route source is RIP
172.16.0.0
First child route
/18
Mask for first child route
120
AD value for RIP routes
1
RIP metric, 1 hop
via 10.10.10.5
Next-hop IP address for this child route
00:00:28
Time since last update from neighbor
Serial0/0/0
Exit interface for first child route
C
Source is connected route
172.16.68.0
Second child route
/22
Mask for second child route
FastEthernet0/0
Exit interface for second child route
