Sorry guys I was busy in Warsaw/Poland teaching a class, the solution is VERY easy,
in this case I have configured an IP SLA to send ICMP echo messages to 12.1.1.1 and
I am also tracking this process. Then I configured an EEM to say if that IP address is
not reachable then remove the network statement from EIGRP, then I had to write
another EEM to say if the IP address is reachable, add the network statement to the
EIGRP. My topology is similar to yours but I used different IP addresses:
R1(S1/2) 12.1.1.1/24 ------ 12.1.1.2/24 (S1/1) R2 (S1/3) 23.1.1.2/24 -----23.1.1.3/24 (S1/2) R3 (S1/4) 34.1.1.3 ----- 34.1.1.4/24 (S1/3) R4
On R1:
R1#sh run int s1/2 | B inter
interface Serial1/2
ip address 12.1.1.1 255.255.255.0
clock rate 64000
router eigrp 1
network 12.1.1.1 0.0.0.0
On R2:
R2#sh run int s1/1 | b inter
interface Serial1/1
ip address 12.1.1.2 255.255.255.0
R2#sh run int s1/3 | b inter
interface Serial1/3
ip address 23.1.1.2 255.255.255.0
clock rate 64000
router eigrp 1
network 12.1.1.2 0.0.0.0
network 23.1.1.2 0.0.0.0
On R3:
R3#sh run int s1/2 | b inter
interface Serial1/2
ip address 23.1.1.3 255.255.255.0
R3#sh run int s1/4 | b inter
interface Serial1/4
ip address 34.1.1.3 255.255.255.0
clock rate 64000
R3#sh run | s router eigrp
router eigrp 1
network 23.1.1.3 0.0.0.0
network 34.1.1.3 0.0.0.0
On R4:
R4#sh run int s1/3 | b inter
interface Serial1/3
ip address 34.1.1.4 255.255.255.0
R4#sh run | s router
router eigrp 1
network 34.1.1.4 0.0.0.0
To verify the configuration:
On R4:
R4#Show ip route eigrp | b Gate
Gateway of last resort is not set
12.0.0.0/24 is subnetted, 1 subnets
12.1.1.0 [90/21536000] via 34.1.1.3, 00:10:23, Serial1/3
23.0.0.0/24 is subnetted, 1 subnets
D
23.1.1.0 [90/21024000] via 34.1.1.3, 00:15:57, Serial1/3
D
NOW, let’s configure R2:
We are going to configure an IP SLA to send ICMP echoes to 12.1.1.1, and start the
process:
ip sla 1
icmp-echo 12.1.1.1 source-interface Serial1/1
frequency 5
ip sla schedule 1 life forever start-time now
Next let’s track this process:
track 2 ip sla 1 reachability
NOW, let’s configure EEM to instruct the router to remove the network statement if
12.1.1.1 is NOT reachable:
event manager applet tst
event track 2 state down
action 1.1 cli command "en"
action 1.2 cli command "conf t"
action 1.3 cli command "router eigrp 1"
action 1.4 cli command "no netw 12.1.1.2 0.0.0.0"
We need to configure another EEM to instruct the router to add the network
statement back when and if the 12.1.1.1 IP address is reachable:
event manager applet tst2
event track 2 state up
action 1.1 cli command "en"
action 1.2 cli command "conf t"
action 1.3 cli command "router eigrp 1"
action 1.4 cli command "netw 12.1.1.2 0.0.0.0"
Cool, let’s test. So far the 12.1.1.1 IP address is reachable so nothing should be done,
let’s verify:
On R3:
R3#Show ip route eigrp | b Gate
Gateway of last resort is not set
D
12.0.0.0/24 is subnetted, 1 subnets
12.1.1.0 [90/21024000] via 23.1.1.2, 00:14:15, Serial1/2
Let’s shutdown the S1/2 interface of R1 and verify:
On R1:
R1(config)#int s1/2
R1(config-if)#Shut
To verify:
On R3:
R3#Show ip route eigrp | b Gate
Gateway of last resort is not set
R3#
As we can see the network is no longer advertised, to verify this further let’s go to
R2 and check EIGRP’s configuration:
On R2:
R2#sh run | s router
router eigrp 1
network 23.1.1.2 0.0.0.0
Cool, now let’s No shut the S1/2 interface of R1:
On R1:
R1(config)#int s1/2
R1(config-if)#No shut
We can see that R2 has added the network statement back, to verify:
On R2:
R2#sh run | s router
router eigrp 1
network 12.1.1.2 0.0.0.0
network 23.1.1.2 0.0.0.0
As a result R3 should see the network:
On R3:
R3#Show ip route eigrp | b Gate
Gateway of last resort is not set
12.0.0.0/24 is subnetted, 1 subnets
D
12.1.1.0 [90/21024000] via 23.1.1.2, 00:00:49, Serial1/2