SCTP listener on solaris switches ip address during handshake

I've a program on solaris 10where a SCTP Server is listening on multi-homed machine (i.e. it has 2 IP interfaces/addresses).

When the remote end, initiates the connections,

INIT  is received on IP Addr 1

INIT ACK goes out from IP Addr 1

Cookie-Echo is received on IP Addr 1

But Cookie Ack goes out from IP Addr 2

The remote end (which is router) doesn't like this and doesn't pass subsequent datachunks.

The question is why solaris switching the ip address during sctp handshake. ( Both the interfaces/addresses are functional

andwork correctly for TCP).