EIGRP STUB CONNECTED

KEY POINTS

On a router from which the EIGRP STUB Connected were enabled, any network address that were propagated or advertise by the Neighboring EIGRP routers will be NOT ADVERTISED on that router from which the STUB Connected is enabled and it will only advertised it’s DIRECTLY CONNECTED NETWORKS.

EIGRP Configurations of MANILA Router:

R1#CONFIG T
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#hostname MANILA
MANILA(config)#int s2/0
MANILA(config-if)#ip address 192.168.12.1 255.255.255.0
MANILA(config-if)#no shut
MANILA(config)#int lo1
MANILA(config-if)#ip add 100.100.100.1 255.255.255.0
MANILA(config-if)#exit

MANILA(config)#router eigrp 12
MANILA(config-router)#network 192.168.12.0
MANILA(config-router)#network 100.100.100.0 0.0.0.255

EIGRP Configurations of MELBOURNE Router:

R2#config t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#hostname MELBOURNE
MELBOURNE(config)#int s2/0
MELBOURNE(config-if)#ip address 192.168.12.2 255.255.255.0
MELBOURNE(config-if)#no shut
MELBOURNE(config-if)#exit
MELBOURNE(config)#int lo1
MELBOURNE(config-if)#ip add 200.200.200.1 255.255.255.0

MELBOURNE(config)#router eigrp 12
MELBOURNE(config-router)#network 192.168.12.0
MELBOURNE(config-router)#network 200.200.200.0 0.0.0.255
MELBOURNE(config-router)#no auto-summary
MELBOURNE(config-router)#exit
MELBOURNE(config-router)#^Z
MELBOURNE#

SINGAPORE ROUTER EIGRP CONFIGURATIONS:

R3#config t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#hostname SINGAPORE
SINGAPORE(config)#int s2/1
SINGAPORE(config-if)#ip add 192.168.23.3 255.255.255.0
SINGAPORE(config-if)#no shut
SINGAPORE(config-if)#int lo1
SINGAPORE(config-if)#ip add 150.150.150.1 255.255.255.0
SINGAPORE(config-if)#exit

SINGAPORE(config)#router eigrp 12
SINGAPORE(config-router)#network 192.168.23.0
SINGAPORE(config-router)#network 150.150.150.0 0.0.0.255
SINGAPORE(config-router)#no auto-summary
SINGAPORE(config-router)#^Z
SINGAPORE#

Now, I will be removing the Default Stub configurations on MELBOURNE Router from the previous configurations.

MELBOURNE#sh run | sec eigrp
router eigrp 12
network 192.168.12.0
network 192.168.23.0
network 200.200.200.0
no auto-summary
eigrp stub connected summary
MELBOURNE#

MELBOURNE#config t
Enter configuration commands, one per line. End with CNTL/Z.
MELBOURNE(config)#router eigrp 12
MELBOURNE(config-router)#no eigrp stub

But before that, let me show the current ROUTING TABLE on the three routers.

> As expected below, MANILA router should see 3 network address ( The loopback address by MELBOURNE and SINGAPORE routers and the network address for the links between MELBOURNE and SINGAPORE Router).

MANILA#sh ip route eigrp
Codes: L – local, 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
       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, H – NHRP, l – LISP
       + – replicated route, % – next hop override

Gateway of last resort is not set

      150.150.0.0/24 is subnetted, 1 subnets
D        150.150.150.0 [90/2809856] via 192.168.12.2, 00:06:52, Serial2/0
D     192.168.23.0/24 [90/2681856] via 192.168.12.2, 00:06:53, Serial2/0
D     200.200.200.0/24 [90/2297856] via 192.168.12.2, 00:06:53, Serial2/0

> Similarly, MELBOURNE Router Routing Table contains the loopback address for both the MANILA and SINGAPORE Routers.

MELBOURNE#sh ip route eigrp
Codes: L – local, 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
       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, H – NHRP, l – LISP
       + – replicated route, % – next hop override

Gateway of last resort is not set

      100.0.0.0/24 is subnetted, 1 subnets
D        100.100.100.0 [90/2297856] via 192.168.12.1, 00:08:18, Serial2/0
      150.150.0.0/24 is subnetted, 1 subnets
D        150.150.150.0 [90/2297856] via 192.168.23.3, 00:08:17, Serial2/1

> And finally, the Routing Table of SINGAPORE Router will have the Loopback Address of MANILA and MELBOURNE Routers and the network address between the links joining MANILA and MELBOURNE Routers.

SINGAPORE#sh ip route eigrp
Codes: L – local, 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
       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, H – NHRP, l – LISP
       + – replicated route, % – next hop override

Gateway of last resort is not set

      100.0.0.0/24 is subnetted, 1 subnets
D        100.100.100.0 [90/2809856] via 192.168.23.2, 00:10:33, Serial2/1
D     192.168.12.0/24 [90/2681856] via 192.168.23.2, 00:10:33, Serial2/1
D     200.200.200.0/24 [90/2297856] via 192.168.23.2, 00:10:33, Serial2/1
SINGAPORE#

NOW, I will be enabling EIGRP STUB CONNECTED on MELBOURNE Router and let’s see the results of the routing table of the three routers.

MANILA#sh run | section eigrp
router eigrp 12
network 100.100.100.0 0.0.0.255
network 192.168.12.0
no auto-summary

MELBOURNE#sh run | sec eigr
router eigrp 12
network 192.168.12.0
network 192.168.23.0
network 200.200.200.0
no auto-summary
eigrp stub connected <<<<<<< I have only enabled EIGRP STUB CONNECTED on MELBOURNE Router.

SINGAPORE#sh run | sec eigrp
router eigrp 12
network 150.150.150.0 0.0.0.255
network 192.168.23.0
no auto-summary

Let’s see the output of the routing table of MELBOURNE, MANILA and SINGAPORE Router.

> As observed, MELBOURNE Routers are still receiving the network address/Loopback address for both the MANILA and the SINGAPORE router. THIS IS THE NORMAL BEHAVIOR FOR STUB CONNECTED ROUTERS.

Gateway of last resort is not set

      100.0.0.0/24 is subnetted, 1 subnets
D        100.100.100.0 [90/2297856] via 192.168.12.1, 00:12:02, Serial2/0
      150.150.0.0/24 is subnetted, 1 subnets
D        150.150.150.0 [90/2297856] via 192.168.23.3, 00:12:01, Serial2/1

Let’s see if SINGAPORE Loopback address is received by the MANILA Router.

Gateway of last resort is not set

D 192.168.23.0/24 [90/2681856] via 192.168.12.2, 00:00:09, Serial2/0
D 200.200.200.0/24 [90/2297856] via 192.168.12.2, 00:00:09, Serial2/0

> As observed, above we notice that MANILA router’s Routing Table does not contain the Loopback address of SINGAPORE but rather it has only learned two EIGRP Routes from MELBOURNE. MELBOURNE ROUTER IS ONLY ADVERTISING THE DIRECTLY CONNECTED NETWORKS.

Let’s see what is SINGAPORE ROUTER’s Routing Table have.

Gateway of last resort is not set

D 192.168.12.0/24 [90/2681856] via 192.168.23.2, 00:01:56, Serial2/1
D 200.200.200.0/24 [90/2297856] via 192.168.23.2, 00:01:56, Serial2/1
SINGAPORE#

> Similarly, as notice the routing table only contains the Directly Connected Network on MELBOURNE ROUTER.

NETWORK LESSON