Delete Multiple Default Gateways

gateway: 

A network gateway is an internetworking system capable of joining together two networks that use different base protocols. A network gateway can be implemented completely in software, completely in hardware, or as a combination of both. Depending on the types of protocols they support, network gateways can operate at any level of the OSI model.

First, obtain how many gateways there are: 

# odmget -q "attribute=route" CuAt

CuAt:
        name = "inet0"
        attribute = "route"
        value = "net,-hopcount,0,,0,192.168.0.2"
        type = "R"
        generic = "DU"
        rep = "s"
        nls_index = 0

CuAt:
        name = "inet0"
        attribute = "route"
        value = "net,-hopcount,0,,0,192.168.0.1"
        type = "R"
        generic = "DU"
        rep = "s"
        nls_index = 0

If there are more than one, you need to remove the excess route: 

# chdev -l inet0 -a delroute="net,-hopcount,0,,0,192.168.0.2"
Method error (/usr/lib/methods/chginet):
        0514-068 Cause not known.
0821-279 writing to routing socket: The process does not exist.
route: not in table or multiple matches
0821-207 chginet: Cannot add route record to CuAt.

Then verify again: 

# odmget -q "attribute=route" CuAt

CuAt:
        name = "inet0"
        attribute = "route"
        value = "net,-hopcount,0,,0,192.168.0.1"
        type = "R"
        generic = "DU"
        rep = "s"
        nls_index = 0