1. Must turn on CDP for all routers; hence this routing protocol is Cisco proprietary.
2. Only works in hub and spoke topology.
3. Has a default administrative distance of 160.
4. Extremely easy to configure.
5. Makes default route easier to configure for every spoke to hub communication. The hub router actually advertises default route to every spoke router using CDP.

IP address parameters for all routers.
R1
interface FastEthernet0/0 ip address 10.0.0.1 255.255.255.248 duplex auto speed auto end interface Loopback1 ip address 1.1.1.1 255.255.255.255 end interface Loopback2 ip address 2.2.2.2 255.255.255.255 end interface Loopback3 ip address 3.3.3.3 255.255.255.255 end
R2
interface FastEthernet0/0 ip address 10.0.0.2 255.255.255.248 duplex auto speed auto end
R3
interface FastEthernet0/0 ip address 10.0.0.3 255.255.255.248 duplex auto speed auto end
R4
interface FastEthernet0/0 ip address 10.0.0.4 255.255.255.248 duplex auto speed auto end
Enable ODR routing, make sure cdp is turned on for every router
R1#sh run | s router router odr R1#
Routing table for all spoke routers
R2#sh ip route odr o* 0.0.0.0/0 [160/1] via 10.0.0.1, 00:00:16, FastEthernet0/0 R2# R3#sh ip route odr o* 0.0.0.0/0 [160/1] via 10.0.0.1, 00:00:33, FastEthernet0/0 R3# R4#sh ip route odr o* 0.0.0.0/0 [160/1] via 10.0.0.1, 00:00:44, FastEthernet0/0 R4#
Reachability test for all spoke routers
R1 reaching int loopback192 of R2 and int loopback172 of R3
R1#ping 172.16.0.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.0.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/12 ms R1# R1#ping 192.168.0.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/8 ms R1#
R2 reachability to int loopback1-3 of R1 and int loopback172 of R3
R2#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms R2#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms R2#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms R2#ping 172.16.0.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.0.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/8/12 ms R2#
R3 reachability to R1,R2 loopback
R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms R3#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/9/16 ms R3#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms R3#ping 192.168.0.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/8 ms R3#
R4 reachability to R1,2,3 loopback
R4#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms R4#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/8 ms R4#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms R4#ping 192.168.0.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms R4#ping 172.16.0.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.0.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/9/16 ms R4#