DMVPN - Dynamic routing tips reminder

EIGRP Summary and Leak Map

Route leaking can be used when you have summarized a subnet but at the same time, you also want to announce a more specific subnet. For my lab, I have used the following design:

• In a first step, I have configured my network without summarization:

R1:

interface Loopback10
 ip address 10.1.0.1 255.255.255.0
!
interface Loopback20
 ip address 10.1.1.1 255.255.255.0
!
interface Loopback30
 ip address 10.1.2.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.168.1.1 255.255.255.0
!
router eigrp 1
 network 10.0.0.0
 network 192.168.1.0

R2:

interface Loopback10

 ip address 192.168.2.2 255.255.255.0

!

interface FastEthernet0/1

 ip address 192.168.1.2 255.255.255.0

!

router eigrp 1

 network 192.168.0.0 0.0.255.255
 

Results (on R2):

R2# show 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

      10.0.0.0/24 is subnetted, 3 subnets

D        10.1.0.0 [90/409600] via 192.168.1.1, 00:01:11, FastEthernet0/1

D        10.1.1.0 [90/409600] via 192.168.1.1, 00:01:11, FastEthernet0/1

D        10.1.2.0 [90/409600] via 192.168.1.1, 00:01:11, FastEthernet0/1

As you can see, 3 subnets are seen in the routing table of R2.

• Now, I have configured summary network on R1:

R1:

interface FastEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 ip summary-address eigrp 1 10.1.0.0 255.255.252.0

Results (on R2):

R2#show 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

      10.0.0.0/22 is subnetted, 1 subnets

D        10.1.0.0 [90/409600] via 192.168.1.1, 00:00:39, FastEthernet0/1

Only one summarized subnet is seen on R2.

• The final step is to configure the route leaking on R1:

R1:

ip access-list standard LEAK-MAP
 permit 10.1.1.0 0.0.0.255
!
route-map LEAK-MAP permit 10
 match ip address LEAK-MAP
!
interface FastEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 ip summary-address eigrp 1 10.1.0.0 255.255.252.0 100 leak-map LEAK-MAP

Results (on R2):

R2#show 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

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

D        10.1.0.0/22 [90/409600] via 192.168.1.1, 00:06:10, FastEthernet0/1

D        10.1.1.0/24 [90/409600] via 192.168.1.1, 00:00:34, FastEthernet0/1

 

Both subnet are seen on R2:

• Summarized (10.1.0.0/22)
• Specific (10.1.1.0/24)

 

For me, it's impossible to realize an equivalent configuration with OSPF.

Don't hesitate to leave a comment if you have already seen this configuration for OSPF.