EGRP Configuration
Last updated
Last updated
The AS (Autonomous System) number must match between routers, or they will not form an adjacency and share route information.
Auto-summary might be enabled or disabled by default, depending on the router/IOS version. If it's enabled, disable it.
The network command will assume a classful address if you don't specify the mask.
EIGRP uses a wildcard mask instead of a regular subnet mask.
A wildcard mask is basically an 'inverted' subnet mask.
All 1s in the subnet mask are 0 in the equivalent wildcard mask. All 0s in the subnet mask are 1 in the equivalent wildcard mask.
/24 | 11111111 | 11111111 | 11111111 | 00000000 |
255 | 255 | 255 | 255 | |
00000000 | 00000000 | 00000000 | 11111111 |
A '0' in the wildcard mask = must match.
A '1' in the wildcard mask = doesn't have to match.
R1 G2/0 IP address:
10101100 . 00010000 . 00000001 . 00001110 = 172.16.1.14
EIGRP network command:
10101100 . 00010000 . 00000001 . 00000000 = 172.16.1.0
00000000 . 00000000 . 00000000 . 00001111 = 0.0.0.15
This means that the first 28 bits must match. They do match, so EIGRP will be activated on the interface.
R1 G2/0 IP address:
10101100 . 00010000 . 00000001 . 00001110 = 172.16.1.14
EIGRP network command:
10101100 . 00010000 . 00000001 . 00000000 = 172.16.1.0
00000000 . 00000000 . 00000000 . 00000111 = 0.0.0.7
They do not match, so EIGRP will not be active in G2/0.
The Router ID order of priority:
Manual configuration.
Highest IP address on a loopback interface.
Highest IP address on a physical interface.
