Let begin with the HQ router, the IP address assigned to the
FastEthernet0/0 is 192.168.20.33 /27. The slash notation means that the subnet
mask is 255.255.255.224.
As I’ve explained earlier on the
Wildcard page, subtract the
above mask from 255.255.255.255.This will result to 0.0.0.31 which will be
your wildcard for Fa0/0 of the HQ router!
For the serial interface, use the same method; /30 means
255.255.255.252 as mask, then subtract this from 255.255.255.255,
the result
will be 0.0.0.3
The Configuration on HQ router will look like this:
HQ#config t
HQ(config)#router ospf 9
HQ(config-router)#network 172.17.10.32 0.0.0.31 area 0
HQ(config-router)#network 10.10.11.8 0.0.0.3 area 0
BR1(config-router)#network 10.10.11.0 0.0.0.3 area 0
HQ(config-router)#end
HQ#
The Configuration on BR1:
BR1#config t
BR1(config)#router ospf 9
BR1(config-router)#network 172.17.10.16 0.0.0.15 area 0
BR1(config-router)#network 10.10.11.0 0.0.0.3 area 0
BR1(config-router)#end
BR1#
BR2#config t
BR2(config)#router ospf 9
BR2(config-router)#network 172.17.10.64 0.0.0.63 area 0
BR2(config-router)#network 10.10.11.8 0.0.0.3 area 0
BR2(config-router)#end
BR2#
When configuring EIGRP, OSPF and ACLs, you will need your
wildcards. To do this properly, you must look at the IP address and the slash
notation “/ ”. This will help you to figure out the subnet, mask and wildcard.
