Hi Siva,
on EXOS you turned auto-negotiation on and advertise only 1000/full.
Are you sure duplex full and speed 1000 does not turn auto-negotiation off on cisco?
Spanningtree or udld could be a problem. You should look at the error counters, fdb,
spanningtree, link state, ..... Turn on logging on IOS and EXOS. Does any happen?
Link los, errors disable, duplicate ip, arp change, TCN, ...?
show ip int brief
show interface
show controllers GigabitEthernet3
....
Regards
Patrick