Configuring route summary addresses for EIGRP.

Configuring route summary addresses for EIGRP.

Route summaries reduce the size of the routing table, improves convergence and cpu load along with memory usage.  We will use the diagram below for our configurations. The data center router has many subnets and we need to aggregate those routes onto the core routers. In order to have a sustainable route summary plan, you need to carefully plan out your ip addressing scheme/subnet assignments.

In order for an EIGRP route summary to be advertised to the neighboring device, you must have at least one interface using one of the subnets in the aggregate and the interface must be up/up. In our case we will use loopback interfaces to simulate this. You can configure multiple aggregate addresses under the interface as we are doing. Unlike OSPF you can summarize on any router, in OSPF you can only perform summarization an ABR or ASBR.

LoopBacks were created before hand and ip's have were assigned. These interfaces need to be associated with the EIGRP process using the network command.

Dist_Data_Center_NJ#show ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            192.168.5.1     YES manual up                    up 
FastEthernet0/1            unassigned      YES unset  administratively down down
Loopback10                 206.200.0.1     YES manual up                    up 
Loopback11                 206.200.5.1     YES manual up                    up 
Dist_Data_Center_NJ#

Associating the new loopback interfaces and future loopbacks.

Dist_Data_Center_NJ(config)#router eigrp 10
Dist_Data_Center_NJ(config-router)# network 206.200.0.0 0.0.3.255
Dist_Data_Center_NJ(config-router)# network 206.200.4.0 0.0.3.255

Confirms which interfaces are park of the EIGRP process.
 
Dist_Data_Center_NJ#show ip eigrp interfaces
IP-EIGRP interfaces for process 10
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              1        0/0        28       0/2          116           0
Lo11               0        0/0         0       0/1            0           0
Lo10               0        0/0         0       0/1            0           0
Dist_Data_Center_NJ#
 

I updated the interface with the summary command, highlighted in red. This will cause your neighborship to re-sync.

Dist_Data_Center_NJ#show run int f0/0
Building configuration...

Current configuration : 212 bytes
!
interface FastEthernet0/0
 ip address 192.168.5.1 255.255.255.252
 ip summary-address eigrp 10 206.200.4.0 255.255.252.0 5
 ip summary-address eigrp 10 206.200.0.0 255.255.252.0 5
 duplex auto
 speed auto
end

CORE_NJ_WAN_1#
*Mar  1 00:09:06.307: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 10: Neighbor 192.168.5.1 (FastEthernet0/0) is resync: peer graceful-restart

CORE_NJ_WAN_1#show ip route
Codes: 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

Gateway of last resort is not set

     192.168.5.0/30 is subnetted, 1 subnets
C       192.168.5.0 is directly connected, FastEthernet0/0
D    206.200.0.0/22 [90/409600] via 192.168.5.1, 00:18:06, FastEthernet0/0
D    206.200.4.0/22 [90/409600] via 192.168.5.1, 00:16:26, FastEthernet0/0