Distance Command on CISCO Router/Switch

Command

Distance

Use

Allows you to filter routes from the routing table. For CCNA purposes, this is usually done through access lists.

Syntax

Router(config-router)#distance <AD> <source IP> <wildcard mask> <access-list>

Options

<Administrative Distance>	Sets the administrative distance for the selected routes
<source IP>	Source IP the route is received from
<wildcard mask>	Specifies a wildcard mask, allows you to specify multiple source IP addresses
<access-list>	Specifies an access-list that selects what routes will have their AD changed

Example

Distance Command on CISCO Router/Switch 1

In this example, we will apply a change to the administrative distance for OSPF to 123 for any route that starts with 1.0.0.0. First, we’ll look at the routing table.

R2(config)#do show ip route ospf
1.0.0.0/32 is subnetted, 3 subnets
O 1.1.1.1 [110/66] via 10.2.2.3, 00:00:22, FastEthernet1/0
O 1.3.3.3 [110/66] via 10.2.2.3, 00:00:22, FastEthernet1/0
O 1.2.2.2 [110/66] via 10.2.2.3, 00:00:22, FastEthernet1/0
192.168.13.0/30 is subnetted, 1 subnets
O 192.168.13.0 [110/65] via 10.2.2.3, 00:00:22, FastEthernet1/0
33.0.0.0/32 is subnetted, 1 subnets
O 33.33.33.33 [110/2] via 10.2.2.3, 00:00:22, FastEthernet1/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/2] via 10.2.2.3, 00:00:22, FastEthernet1/0
111.0.0.0/32 is subnetted, 1 subnets
O 111.111.111.111 [110/66] via 10.2.2.3, 00:00:22, FastEthernet1/0
10.0.0.0/24 is subnetted, 3 subnets
O 10.4.4.0 [110/65] via 10.2.2.3, 00:00:22, FastEthernet1/0
11.0.0.0/32 is subnetted, 1 subnets
O 11.11.11.11 [110/66] via 10.2.2.3, 00:00:22, FastEthernet1/0
133.133.0.0/32 is subnetted, 1 subnets
O 133.133.133.133 [110/2] via 10.2.2.3, 00:00:22, FastEthernet1/0

Now, we will configure the distance command on R2’s OSPF process.

R2(config)#access-list 25 permit 1.0.0.0 0.255.255.255
R2(config)#router ospf 1
R2(config-router)#distance 123 10.1.1.1 255.255.255.255 25

Finally, we see routes starting with 1.0.0.0 now have an administrative distance of 123.

R2(config-router)#do show ip route ospf
1.0.0.0/32 is subnetted, 3 subnets
O 1.1.1.1 [123/2] via 10.1.1.1, 00:00:03, FastEthernet0/0
O 1.3.3.3 [123/2] via 10.1.1.1, 00:00:03, FastEthernet0/0
O 1.2.2.2 [123/2] via 10.1.1.1, 00:00:03, FastEthernet0/0
192.168.13.0/30 is subnetted, 1 subnets
O 192.168.13.0 [110/65] via 10.2.2.3, 00:00:03, FastEthernet1/0
[110/65] via 10.1.1.1, 00:00:03, FastEthernet0/0