R2#


interface FastEthernet0/1
 ip address 200.1.1.2 255.255.255.0
 no ip proxy-arp
 ip irdp
 ip irdp maxadvertinterval 10
 ip irdp minadvertinterval 10
 ip irdp holdtime 30
 ip irdp preference 100
 duplex auto
 speed auto
!

interface BVI1
 ip address 17.57.100.3 255.255.255.0
 no ip proxy-arp
 ip irdp
 ip irdp maxadvertinterval 10
 ip irdp minadvertinterval 10
 ip irdp holdtime 30
!

R4#sh run | i ip gdp
ip gdp irdp    <----------also on R7 and S5
R4#