Cisco CCNP and CCIE Study Notes

On-demand Routing (ODR) is an interesting option for use in hub and spoke configurations. This is a subject that is included in the CCIE and CCNP exams but it is my impression that this gets short shrift in the usual preparation material for these exams. This blog post poses a problem that occurs while running ODR in a small network.


Consider the above network with one hub and two spoke routers. The hub router is running ODR. The configuration of the three routers is given below

HUB

hostname HUB
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Serial2
 ip address 23.1.1.1 255.255.255.0
 encapsulation frame-relay
 frame-relay map ip 23.1.1.2 223
 frame-relay interface-dlci 223
 no frame-relay inverse-arp
!
router odr
!
ip classless

SPOKE1

hostname SPOKE1
!
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Ethernet0
 ip address 12.1.1.1 255.255.255.0

SPOKE2

hostname SPOKE2
!
interface Loopback0
 ip address 3.3.3.3 255.255.255.0
!
interface Serial2
 ip address 23.1.1.2 255.255.255.0
 encapsulation frame-relay
 frame-relay map ip 23.1.1.1 322
 frame-relay interface-dlci 322
 no frame-relay inverse-arp

Now when the routing table on the HUB router is checked, we see the following

HUB#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     1.0.0.0/24 is subnetted, 1 subnets
o       1.1.1.0 [160/1] via 12.1.1.1, 00:00:08, Ethernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
C       2.2.2.2 is directly connected, Loopback0
     23.0.0.0/24 is subnetted, 1 subnets
C       23.1.1.0 is directly connected, Serial2/0
     12.0.0.0/24 is subnetted, 1 subnets
C       12.1.1.0 is directly connected, Ethernet0/0

Note that there is an ODR route to 1.1.1.1/32 as we expect but none to 3.3.3.3/32 as would have been expected.

What is the reason for the missing ODR learnt route to 3.3.3.3/32? How can this be fixed such that an ODR route to 3.3.3.3/32 gets installed in the routing table of the HUB router?