Router R3 is connected on it's ethernet interface to SW3 (working only as a l2 switch) and we have to send him default gateway via IRDP. This how such configuration would looks like:
R3
R3#sh run int fast 0/0.50
Building configuration...
Current configuration : 262 bytes
!
interface FastEthernet0/0.50
encapsulation dot1Q 50
ip address 172.16.30.3 255.255.255.128
ip irdp
ip irdp multicast
ip irdp maxadvertinterval 20
ip irdp minadvertinterval 20
ip irdp holdtime 60
ip irdp preference 100
ip irdp address 0.0.0.0 100
end
R3#
and
SW3#sh run int vlan 50
Building configuration...
Current configuration : 93 bytes
!
interface Vlan50
ip address 172.16.30.10 255.255.255.128
ip irdp
ip irdp multicast
end
SW3#
however, to make it work you'd need to enable it by entering
ip gdp irdp
SW3#show ip route
Gateway Using Interval Priority Interface
172.16.30.3 IRDP 20 100 Vlan50
Default gateway is 172.16.30.3
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
SW3#
