EIGRP Stub

When using the EIGRP Stub Routing feature, you need to configure the distribution and remote routers to use EIGRP, and to configure only the remote router as a stub. Only specified routes are propagated from the remote (stub) router. The router responds to queries for summaries, connected routes, redistributed static routes, external routes, and internal routes with the message "inaccessible." A router that is configured as a stub will send a special peer information packet to all neighboring routers to report its status as a stub router. 

Any neighbor that receives a packet informing it of the stub status will not query the stub router for any routes, and a router that has a stub peer will not query that peer. The stub router will depend on the distribution router to send the proper updates to all peers. 

Passive Interface in EIGRP and OSPF

As an extention to the previous lab we also configure OSPF in the above network. So we have both EIGRP and OSPF on both the routers. In order for the routers to choose OSPF over EIGRP we reduce the AD of OSPF from 110 to 5.

Tip: Configure the loopbacks under OSPF point-to-point network. Otherwise OSPF will make them  a /32 network no matter what the actual subnet is.

Now we will check the effect of passive-interface command in OSPF.
1. Enable wireshark capture on R3 fa0/0. Also turn on debug commands on routers.
2. Make fa0/0 on R2 a OSPF passive-interface
3. OSPF drops off and EIGRP kicks in.

*Mar  1 13:39:58.352: %OSPF-5-ADJCHG: Process 1, Nbr 120.120.120.120 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
R2#
*Mar  1 13:39:59.788: %SYS-5-CONFIG_I: Configured from console by console
R2#
*Mar  1 13:40:03.868: IP-EIGRP(Default-IP-Routing-Table:1): route installed for 110.110.110.0  ()
*Mar  1 13:40:03.872: IP-EIGRP(Default-IP-Routing-Table:1): route installed for 120.120.120.0  ()
*Mar  1 13:40:03.872: IP-EIGRP(Default-IP-Routing-Table:1): route installed for 100.100.100.100  ()
Sh ip route output before:
Gateway of last resort is not set

     100.0.0.0/32 is subnetted, 1 subnets
O IA    100.100.100.100 [5/11] via 23.23.23.2, 00:00:06, FastEthernet0/0
     33.0.0.0/24 is subnetted, 1 subnets
C       33.33.33.0 is directly connected, Loopback3
     23.0.0.0/30 is subnetted, 1 subnets
C       23.23.23.0 is directly connected, FastEthernet0/0
     22.0.0.0/24 is subnetted, 1 subnets
C       22.22.22.0 is directly connected, Loopback2
     110.0.0.0/24 is subnetted, 1 subnets
O IA    110.110.110.0 [5/11] via 23.23.23.2, 00:00:06, FastEthernet0/0
     10.0.0.0/24 is subnetted, 1 subnets
C       10.10.10.0 is directly connected, Loopback0
     11.0.0.0/24 is subnetted, 1 subnets
C       11.11.11.0 is directly connected, Loopback1
     120.0.0.0/24 is subnetted, 1 subnets
O IA    120.120.120.0 [5/11] via 23.23.23.2, 00:00:08, FastEthernet0/0

Sh ip route output after:

Gateway of last resort is not set

     100.0.0.0/32 is subnetted, 1 subnets
D       100.100.100.100 [90/409600] via 23.23.23.2, 00:02:21, FastEthernet0/0
     33.0.0.0/24 is subnetted, 1 subnets
C       33.33.33.0 is directly connected, Loopback3
     23.0.0.0/30 is subnetted, 1 subnets
C       23.23.23.0 is directly connected, FastEthernet0/0
     22.0.0.0/24 is subnetted, 1 subnets
C       22.22.22.0 is directly connected, Loopback2
     110.0.0.0/24 is subnetted, 1 subnets
D       110.110.110.0 [90/409600] via 23.23.23.2, 00:02:21, FastEthernet0/0
     10.0.0.0/24 is subnetted, 1 subnets
C       10.10.10.0 is directly connected, Loopback0
     11.0.0.0/24 is subnetted, 1 subnets
C       11.11.11.0 is directly connected, Loopback1
     120.0.0.0/24 is subnetted, 1 subnets
D       120.120.120.0 [90/409600] via 23.23.23.2, 00:02:22, FastEthernet0/0





R3 fa0/0 is still receiving hello packets fro R3 fa0/0.. Since R3 is the DR router but there is no response from the other end..