EIGRP IPv4 - Summarization
Summarization
EIGRP (Enhanced Interior Gateway Routing Protocol) IPv4 summarization is a technique used to optimize routing tables and reduce the size of updates by aggregating multiple contiguous subnets into a single summary route. Summarization in EIGRP helps improve network scalability and efficiency by minimizing the number of routes exchanged between routers. When configuring summarization, administrators use the 'summary-address' command to define a summary route along with its corresponding subnet mask. This process allows EIGRP routers to advertise the summarized route instead of individual subnets, conserving bandwidth and reducing the memory requirements for routing tables. Careful consideration is essential when implementing summarization to ensure that the summarization boundaries align with the network topology and do not inadvertently cause suboptimal routing or connectivity issues. EIGRP IPv4 summarization is a valuable tool in large networks with diverse subnets, contributing to more streamlined routing processes and improved overall network performance.
Lab:
Disclaimer
This Configuration Guide is designed to assist members to enhance their skills in particular technology area. While every effort has been made to ensure that all material is as complete and accurate as possible, the enclosed material is presented on an Dzas isdz basis. Neither the authors nor Forum assume any liability or responsibility to any person or entity with respect to loss or damages incurred from the information contained in this guide. This configuration guide was developed by Forum. Any similarities between material presented in this configuration guide and any other material is completely coincidental.
Cisco IOS Software, Linux Software (I86BI_LINUX-ADVENTERPRISEK9-M), Version 15.2(4)M1, DEVELOPMENT TEST SOFTWARE
Task 1: Configure IPv4 EIGRP Summarization
Step 1: In the configuration mode of router configure 4 loopbacks with network address in sequence
R1:
interface loopback 1
ip address 11.0.0.1 255.255.255.0
exit
interface loopback 2
ip address 11.0.1.1 255.255.255.0
exit
interface loopback 3
ip address 11.0.2.1 255.255.255.0
exit
interface loopback 4
ip address 11.0.3.1 255.255.255.0
exit
Step 2: Disable auto-summarization in EIGRP Process & verify routes on neighbor router routing table
R1:
router eigrp 100
no auto-summary
exit
R2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGPF: GDOI is OFF
*M
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area.1 (Seri
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
D 11.0.0.0 [90/2297856] via 12.0.0.1, 01:27:34, Serial2/0
D 11.0.1.0 [90/2297856] via 12.0.0.1, 01:27:34, Serial2/0
D 11.0.2.0 [90/2297856] via 12.0.0.1, 01:27:34, Serial2/0
D 11.0.3.0 [90/2297856] via 12.0.0.1, 01:03:44, Serial2/0
12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 12.0.0.0/24 is directly connected, Serial2/0
C 22.0.1.0/24 is directly connected, Loopback1
L 22.0.0.2/32 is directly connected, Loopback1
C 22.0.1.0/24 is directly connected, Loopback2
L 22.0.1.2/32 is directly connected, Loopback2
C 22.0.2.0/24 is directly connected, Loopback3
L 22.0.2.2/32 is directly connected, Loopback3
C 22.0.3.0/24 is directly connected, Loopback4
L 22.0.3.2/32 is directly connected, Loopback4
33.0.0.0/24 is subnetted, 4 subnets
D 33.0.0.0 [90/409600] via 23.0.0.3, 01:27:32, Ethernet0/0
D 33.0.1.0 [90/409600] via 23.0.0.3, 01:27:32, Ethernet0/0
D 33.0.2.0 [90/409600] via 23.0.0.3, 01:27:32, Ethernet0/0
D 33.0.3.0 [90/409600] via 23.0.0.3, 00:41:32, Ethernet0/0
44.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D 44.0.0.0 [90/2323456] via 23.0.0.3, 00:33:37, Ethernet0/0
D 44.0.1.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
D 44.0.2.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
D 44.0.3.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
Step 3: Summarize EIGRP routes outgoing interfaces
R1:
interface serial 2/0
ip summary-address eigrp 100 11.0.0.0 255.255.252.0
exit
Summarization is configurable on a per-interface basis in any router within network. Router R1 sends summary of 11.0.0.0 network on interface s2/0
Task 2: Verification: Step 1: Verify receipt of summary route in neighbor routing table by following command:
R2#show ip route
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
11.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D 11.0.0.0/22 [90/2297856] via 12.0.0.1, 00:21:50, Serial2/0
12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 12.0.0.0/24 is directly connected, Serial2/0
L 12.0.0.2/32 is directly connected, Serial2/0
22.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
C 22.0.0.0/24 is directly connected, Loopback1
L 22.0.0.2/32 is directly connected, Loopback1
C 22.0.1.0/24 is directly connected, Loopback2
L 22.0.1.2/32 is directly connected, Loopback2
C 22.0.2.0/24 is directly connected, Loopback3
L 22.0.2.2/32 is directly connected, Loopback3
C 22.0.3.0/24 is directly connected, Loopback4
L 22.0.3.2/32 is directly connected, Loopback4
23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 23.0.0.0/24 is directly connected, Ethernet0/0
L 23.0.0.2/32 is directly connected, Ethernet0/0
33.0.0.0/24 is subnetted, 4 subnets
D 33.0.0.0 [90/409600] via 23.0.0.3, 01:06:04, Ethernet0/0
D 33.0.1.0 [90/409600] via 23.0.0.3, 01:51:52, Ethernet0/0
D 33.0.2.0 [90/409600] via 23.0.0.3, 01:51:52, Ethernet0/0
D 33.0.3.0 [90/409600] via 23.0.0.3, 01:51:52, Ethernet0/0
34.0.0.0/24 is subnetted, 1 subnets
D 34.0.0.0 [90/2195456] via 23.0.0.3, 01:51:52, Ethernet0/0
44.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D 44.0.0.0 [90/2323456] via 23.0.0.3, 00:33:37, Ethernet0/0
D 44.0.1.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
D 44.0.2.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
D 44.0.3.0 [90/2835456] via 23.0.0.3, 01:10:08, Ethernet0/0
Summarized routes is received from neighbor router.
Step 2: Verify creation of null interface in routing table:
R1#show ip route
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
11.0.0.0/8 is variably subnetted, 9 subnets, 3 masks
D 11.0.0.0/22 is a summary, 00:23:54, Null0
C 11.0.0.0/24 is directly connected, Loopback1
L 11.0.0.1/32 is directly connected, Loopback1
C 11.0.1.0/24 is directly connected, Loopback2
L 11.0.1.1/32 is directly connected, Loopback2
C 11.0.2.0/24 is directly connected, Loopback3
L 11.0.2.1/32 is directly connected, Loopback3
C 11.0.3.0/24 is directly connected, Loopback4
L 11.0.3.1/32 is directly connected, Loopback4
12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 12.0.0.0/24 is directly connected, Serial2/0
L 12.0.0.1/32 is directly connected, Serial2/0
22.0.0.0/24 is subnetted, 4 subnets
D 22.0.0.0 [90/2297856] via 12.0.0.2, 01:53:58, Serial2/0
D 22.0.1.0 [90/2297856] via 12.0.0.2, 01:53:58, Serial2/0
D 22.0.2.0 [90/2297856] via 12.0.0.2, 01:53:58, Serial2/0
D 22.0.3.0 [90/2297856] via 12.0.0.2, 01:20:30, Serial2/0
23.0.0.0/24 is subnetted, 1 subnets
D 23.0.0.0 [90/2195456] via 12.0.0.2, 01:53:58, Serial2/0
33.0.0.0/24 is subnetted, 4 subnets
D 33.0.0.0 [90/2323456] via 12.0.0.2, 01:53:56, Serial2/0
D 33.0.1.0 [90/2323456] via 12.0.0.2, 01:53:56, Serial2/0
D 33.0.2.0 [90/2323456] via 12.0.0.2, 01:53:56, Serial2/0
D 33.0.3.0 [90/2323456] via 12.0.0.2, 01:08:08, Serial2/0
34.0.0.0/24 is subnetted, 1 subnets
D 34.0.0.0 [90/2707456] via 12.0.0.2, 01:53:56, Serial2/0
44.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D 44.0.0.0 [90/2323456] via 12.0.0.2, 00:33:37, Serial2/0
D 44.0.1.0 [90/2835456] via 12.0.0.2, 01:10:08, Serial2/0
D 44.0.2.0 [90/2835456] via 12.0.0.2, 01:10:08, Serial2/0
D 44.0.3.0 [90/2835456] via 12.0.0.2, 01:10:08, Serial2/0
When summarization is configured on a router, same router immediately created a routing point to Null 0 for loop prevention.