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8. OSPF ROUTE SUMMARIZATION

HOW TO OSPF ROUTE SUMMARIZATION CONFIGURATION
 
Interface IP Address Configuration  
  
R1  
  
Interface  IP Address  Subnet Mask  
S0/2/0      1.1.1.1          255.0.0.0  
E 0            10.1.1.1       255.0.0.0  
  
R2  
  
Interface  IP Address   Subnet Mask 
 
S0             1.1.1.2           255.0.0.0  
S1             2.2.2.1           255.0.0.0  
E0             20.1.1.1         255.0.0.0  
  
R3  
  
Interface        IP Address       Subnet Mask  
S0                   2.2.2.2              255.0.0.0  
E 0                  30.1.1.1            255.0.0.0  
Loopback 0  172.168.0.1      255.255.255.0  
Loopback 1  172.168.1.1      255.255.255.0  
Loopback 2  172.168.2.1      255.255.255.0  
Loopback 3  172.168.3.1      255.255.255.0  
  
Task 1 : Configure Route Summarization at ABR  
  
Configure OSPF in Area 0 on R1 ( S0/2/0, E0 ), R2 ( S0 ).  
Configure OSPF in Area 1 on R2 ( S1 ), R3 ( S0, E0, Loopback 0 – 3 ).
 
Create the following Loopbacks on R3:  
  
     Loopback 0 – 172.168.0.1/24  
     Loopback 1 – 172.168.1.1/24  
     Loopback 2 – 172.168.2.1/24  
     Loopback 3 – 172.168.3.1/24  
       
Advertise these newly created loopbacks in OSPF using the network command. Make  
sure they appear in the routing table using a /24 mask.  These routes should be seen as a  
single summarized route outside of area 1.  
  
R3                                                              
                                                                  
Int loopback 0                                                    
Ip add 172.168.0.1 255.255.255. 0                                 
Ip ospf network point-to-point                                    
  
Int loopback 1  
Ip add 172.168.1.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Int loopback 2  
Ip add 172.168.2.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Int loopback 3  
Ip add 172.168.3.1 255.255.255. 0  
Ip ospf network point-to-point  
 
Router ospf 1  
Network 172.168.0.0 0.0.255.255 area 1  
Network 2.2.2.2 0.0.0.0 area 1  
Network 30.0.0.0 0.255.255 area 1 
 
 
R2
 
Router ospf 1 
Area 1 range172.168.0.0 255.255.252.0
 
  
R1#show ip route  
  
The output displays a smaller routing table by displaying only one summarized route for  
the contiguous networks.
 
 
Task 2 : Configure Route Summarization At ASBR  
  
(Scenario Based On Task 1)  
  
Configure OSPF on the routers as per the above scenario.  
Create the following Loopbacks on R3:  
  
     Loopback 0 – 172.168.0.1/24  
     Loopback 1 – 172.168.1.1/24  
     Loopback 2– 172.168.2.1/24  
     Loopback 3 – 172.168.3.1/24  
       
Advertise these newly created loopbacks in EIGRP AS 100 using the network command  
and redistribute these networks into OSPF Area 1. These routes should be seen as a single  
summarized route.
 
R3  
  
Int loopback 0  
Ip add 172.168.0.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Int loopback 1  
Ip add 172.168.1.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Int loopback 2  
Ip add 172.168.2.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Int loopback 3  
Ip add 172.168.3.1 255.255.255. 0  
Ip ospf network point-to-point  
  
Router ospf 1  
Network 2.2.2.2 0.0.0.0 area 1  
Network 30.0.0.0 0.255.255 area 1  
  
Router eigrp 100  
Network 172.168.0.0  
No auto-summary  
  
Router ospf 1  
Redistribute eigrp 100 metric 10 subnets  
Summary-address 172.168.0.0 255.255.252.0
 
Verification:   
  
R2#show ip route  
  
The output displays a smaller routing table.   
  
R3#show ip route  
  
The output displays a smaller routing table.   
  
R3#show ip route  
  
The output displays a summary route pointing to interface null 0 on R3 routing table.  
This is automatically generated by default, when manual summarization is configured so  
as to prevent routing loops.
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