Tuesday, October 22, 2013

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.



 

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3 comments:

  1. RodrigoOctober 24, 2013 at 1:19 PM

    In fact, with OSPF the following configuration can be used:

    R1:
    ==

    router ospf 1
    router-id 1.1.1.1
    summary-address 10.1.0.0 255.255.252.0
    summary-address 10.1.1.0 255.255.255.0
    redistribute connected subnets
    network 192.168.1.0 0.0.0.255 area 0


    On R2, we can see:
    10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
    O E2 10.1.0.0/22 [110/20] via 192.168.1.1, 00:05:48, FastEthernet0/1
    O E2 10.1.1.0/24 [110/20] via 192.168.1.1, 00:00:07, FastEthernet0/1

    ReplyDelete
    Replies
    1. UnknownDecember 14, 2013 at 1:06 PM

      This configuration is only on ASBR when you are summarizing externet routes. What about summarizing OSPF intra-area routes on ABR?

      Delete
    2. RodrigoDecember 14, 2013 at 1:36 PM

      Hello,

      I have just tested it with the following configuration:
      router ospf 1
      router-id 1.1.1.1
      log-adjacency-changes
      area 1 range 10.1.1.0 255.255.255.0
      area 1 range 10.1.0.0 255.255.252.0
      network 10.1.0.0 0.0.255.255 area 1
      network 192.168.1.0 0.0.0.255 area 0


      As you can see, we have the same behavior with an ABR on R2:
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
      O IA 10.1.0.0/22 [110/11] via 192.168.1.1, 00:00:28, FastEthernet0/1
      O IA 10.1.1.0/24 [110/11] via 192.168.1.1, 00:00:05, FastEthernet0/1


      Delete

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