The Enhanced Interior Gateway Routing Protocol (EIGRP) supports secondary addresses. However, since EIGRP sources data packets from the primary address, all the routers should be configured with the primary addresses that belong on the same subnet.
EIGRP only forms neighbors over the primary network. Be sure that the primary address on the interface is configured for EIGRP by issuing the network command under the router eigrp configuration command. This network should include the primary address of the interface which runs EIGRP.
This is an example:
interface e0 ip address 172.16.3.1 255.255.255.0 ip address 220.127.116.11 255.255.255.0 secondary
router eigrp 7 network 172.16.0.0 !-- This network covers the address assigned to interface e0. network 18.104.22.168
The 22.214.171.124 network covers the secondary IP address assigned to interface e0. Although the 126.96.36.199 network is also included in EIGRP, EIGRP will not form a neighbor over this network. However, the 188.8.131.52 network is advertised through EIGRP.If there is a mismatch between the primary address configured on the interfaces there occurs "not on common subnet for Ethernet0" error message.