EIGRP

[jonk34567]

in eigrp  what is difference if we use wildcard mask and not using  it

[Julio E. Moisa]

Hi

None, Actually the wildcard will be always the results, for example if you configure the network statement using the subnet mask:

router eigrp 100

network 10.0.0.0 255.255.255.0   <---- subnet mask

EIGRP will automatically change or convert it to the wildcard, it can be seen through show run. once it is applied. It is used to specify the network segment or size of a network or to apply an action to specific bits.

:-)

[Philip D'Ath]

If you don't use it [I think] it uses the classfull mask.  Configuring it allows you to make it something other than the classfull mask.

[Deepak Kumar]

I checked in the lab and it's not showing any difference if you have a single subnet. 

See the example:

Router R1 running configuration as below:

interface Loopback1
ip address 10.10.10.1 255.255.255.0
!
interface Loopback12
ip address 192.168.1.1 255.255.255.128
!
interface GigabitEthernet0/0
ip address 1.1.1.1 255.255.255.0
duplex auto
speed auto

!

router eigrp 1
network 1.1.1.0 0.0.0.255
network 10.0.0.0 --------- (My actual configuration was 10.10.10.0)
network 192.168.1.0

Now I am checking routing table on R2 router. (Here, I am not putting any r2 configuration because my complete LAB is deepened on R1 configuration).

Gateway of last resort is not set

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 1.1.1.0/24 is directly connected, GigabitEthernet0/0

L 1.1.1.2/32 is directly connected, GigabitEthernet0/0

10.0.0.0/24 is subnetted, 1 subnets

D 10.10.10.0/24 [90/130816] via 1.1.1.1, 00:10:43, GigabitEthernet0/0

20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 20.20.20.0/24 is directly connected, Loopback1

L 20.20.20.1/32 is directly connected, Loopback1

192.168.1.0/25 is subnetted, 1 subnets

D 192.168.1.0/25 [90/130816] via 1.1.1.1, 00:07:43, GigabitEthernet0/0

I am going to create a new loopback interface on R1 router with IP address 192.168.1.130/25

!

interface Loopback100

ip address 192.168.1.130 255.255.255.128

!

Now look the routing table on R2.

Gateway of last resort is not set

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 1.1.1.0/24 is directly connected, GigabitEthernet0/0

L 1.1.1.2/32 is directly connected, GigabitEthernet0/0

10.0.0.0/24 is subnetted, 1 subnets

D 10.10.10.0/24 [90/130816] via 1.1.1.1, 00:14:30, GigabitEthernet0/0

20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 20.20.20.0/24 is directly connected, Loopback1

L 20.20.20.1/32 is directly connected, Loopback1

192.168.1.0/25 is subnetted, 2 subnets

D 192.168.1.0/25 [90/130816] via 1.1.1.1, 00:11:30, GigabitEthernet0/0

D 192.168.1.128/25 [90/130816] via 1.1.1.1, 00:00:52, GigabitEthernet0/0

Result:

If you are not going to configure the wildcard mask then its consider as classful. It will send all classless subnets to the neighbour. 

Regards,

Deepak Kumar 

[Julio E. Moisa]

Hi

Have you verified if no auto-summary is running? it is applied by default.

:-)

[Deepak Kumar]

Yes, I was.

Regards,
Deepak Kumar