Configuring OSPF Route Summarization

In this lab you will learn how to configure an Open Shortest Path First (OSPF) Inter-Area route summary on an ABR to advertise upstream neighbors as a single route prefix.

Real World Application & Core Knowledge

If you have completed Lab 7-8 – Configuring RIP Route Summarization and Lab 8-8 – Configuring EIGRP Route Summarization
then you’re no stranger to configuring route summarization.

In a nut shell, route summarization is the process of summarizing subnets into a larger subnet to be advertised to upstream routers for ease of management/troubleshooting and resource conservation.
Familiarize yourself with the following new command(s);

However when working with OSPF you can only summarize at an ABR or ASBR. There are two types of summarization in OSPF; Inter-Area Summarization and External Summarization.

Inter-Area route summarization can only be done on the Area Boarder Router (ABR) and summarize routes from a particular area into the backbone area.

External Route summarization can only be done on an ASBR and summarizes routes to an external destination.

To configure Inter-Area summarization, you’ll use the area # network netmask command in OSPF router configuration mode. This command can only be issued on an ABR.

To configure External Route summarization you’d use the summary-address network netmask command in router configuration mode. This command can be executed on any OSPF router but will only function on ASBR’s.

In this lab you’re going to create 4 new loopback interfaces on R4 located in Area 44 then create a summary route advertising all 4 routes as a single route into the backbone area.

Familiarize yourself with the following new command(s);

area # network netmask – This command is executed in OSPF router configuration mode on an Area Boarder Router (ABR) to configure Inter-Area route summarization. These summary routes will be advertised into the OSPF backbone area (Area 0).

summary-address network netmask – This command is executed in OSPF router configuration mode on an Autonomous System Boundary Router (ASBR) to configure External route summarization.

The following logical topology shown below is used in labs found through out Section 9 – Configuring OSPF;

Lab Prerequisites

• If you completed lab 9-13 you can start where you’ve left off or you can load the Free CCNA Workbook GNS3 topology; start and establish a console session with R1, R2, R3, R4, R5 and SW1 then load their initial configurations included below by copying the config from the textbox and pasting it into the routers console.

Initial Configurations

!################################################## !#  Free CCNA Workbook Lab 9-13 R1 Initial Config # !################################################## ! enable configure terminal ! hostname R1 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.10.1 255.255.255.0  ip ospf 1 area 1 ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.1 255.255.255.248  ip ospf 1 area 0  encapsulation frame-relay  serial restart-delay 0  frame-relay map ip 10.1.245.5 125 broadcast  frame-relay map ip 10.1.245.4 124 broadcast  frame-relay map ip 10.1.245.2 122 broadcast  no frame-relay inverse-arp  no shut  exit ! router ospf 1  router-id 1.1.1.1  log-adjacency-changes  auto-cost reference-bandwidth 100000  maximum-paths 1  neighbor 10.1.245.2  neighbor 10.1.245.4  neighbor 10.1.245.5 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-14 R2 Initial Config # !################################################## ! enable configure terminal ! hostname R2 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.20.1 255.255.255.0  ip ospf 1 area 2 ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.2 255.255.255.248  encapsulation frame-relay  ip ospf priority 0 ip ospf 1 area 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 221 broadcast  frame map ip 10.1.245.4 221  frame map ip 10.1.245.5 221  no shut ! interface Serial1/2  ### POINT-TO-POINT LINK TO R3 ###  ip address 10.1.23.1 255.255.255.252  ip ospf 1 area 3  ip ospf hello-interval 1  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  router-id 2.2.2.2  auto-cost reference-bandwidth 100000  log-adjacency-changes  area 3 stub no-summary ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-14 R3 Initial Config # !################################################## ! enable configure terminal ! hostname R3 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.30.1 255.255.255.0  ip ospf 1 area 3 ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R2 ###  ip address 10.1.23.2 255.255.255.252  ip ospf 1 area 3  ip ospf hello-interval 1  encapsulation ppp  no shut  exit ! router ospf 1  router-id 3.3.3.3  log-adjacency-changes  auto-cost reference-bandwidth 100000  area 3 stub ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-14 R4 Initial Config # !################################################## ! enable configure terminal ! hostname R4 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.40.1 255.255.255.0  ip ospf 1 area 4 ! interface FastEthernet0/0  description ### REAL NETWORK ###  ip address 10.45.1.1 255.255.255.0  ip ospf 1 area 45  no shut ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.4 255.255.255.248  encapsulation frame-relay  ip ospf priority 0  ip ospf 1 area 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 421 broadcast  frame map ip 10.1.245.2 421  frame map ip 10.1.245.5 421  no shut ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R5 ###  ip address 10.1.45.1 255.255.255.252  ip ospf 1 area 45  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  router-id 4.4.4.4  auto-cost reference-bandwidth 100000  log-adjacency-changes  passive-interface fastethernet0/0 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-14 R5 Initial Config # !################################################## ! enable configure terminal ! hostname R5 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.50.1 255.255.255.0  ip ospf 1 area 5 ! interface FastEthernet0/0  description ### REAL NETWORK ###  ip address 10.45.1.2 255.255.255.0  ip ospf cost 65535  ip ospf 1 area 45  no shut ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.5 255.255.255.248  encapsulation frame-relay  ip ospf priority 0  ip ospf 1 area 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 521 broadcast  frame map ip 10.1.245.2 521  frame map ip 10.1.245.4 521  no shut ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R4 ###  ip address 10.1.45.2 255.255.255.252  ip ospf 1 area 45  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  router-id 5.5.5.5  log-adjacency-changes  auto-cost reference-bandwidth 100000  passive-interface fastethernet0/0 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-X SW1 Initial Config # !################################################## ! enable configure terminal ! hostname SW1 no ip domain-lookup ! line con 0  logging sync  no exec-timeout ! end

Lab Objectives

• Create 4 new loopback interfaces on R4 located in Area 44 using the ip addresses 10.44.4.0/24, 10.44.5.0/24, 10.44.6.0/24 and 10.44.7.0/24
• Configure R4 to advertise a single Inter-Area summary route into the OSPF backbone that encompasses all 4 routes.
• Verify that the summary route is being propagated correctly by viewing the routing table on R1.

Lab Instruction

Objective 1. – Create 4 new loopback interfaces on R4 located in Area 44 using the ip addresses 10.44.4.0/24, 10.44.5.0/24, 10.44.6.0/24 and 10.44.7.0/24

R4#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R4(config)#interface loopback4 R4(config-if)# %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback4, changed state to up R4(config-if)#ip add 10.44.4.1 255.255.255.0 R4(config-if)#ip ospf 1 area 44 R4(config-if)#interface loopback5 %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback5, changed state to up R4(config-if)#ip add 10.44.5.1 255.255.255.0 R4(config-if)#ip ospf 1 area 44 R4(config-if)#interface loopback6 %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback6, changed state to up R4(config-if)#ip add 10.44.6.1 255.255.255.0 R4(config-if)#ip ospf 1 area 44 R4(config-if)#interface loopback7 %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback7, changed state to up R4(config-if)#ip add 10.44.7.1 255.255.255.0 R4(config-if)#ip ospf 1 area 44 R4(config-if)#end R4#

Objective 2. – Configure R4 to advertise a single Inter-Area summary route into the OSPF backbone that encompasses all 4 routes.

R4#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R4(config)#router ospf 1 R4(config-router)#area 44 range 10.44.4.0 255.255.252.0 R4(config-router)#end R4# %SYS-5-CONFIG_I: Configured from console by console R4#

Objective 3. – Verify that the summary route is being propagated correctly by viewing the routing table on R1.

R1#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

    10.0.0.0/8 is variably subnetted, 10 subnets, 5 masks
O IA    10.55.50.1/32 [110/64767] via 10.1.245.5, 00:43:29, Serial1/0
O IA    10.55.40.1/32 [110/64767] via 10.1.245.4, 00:43:29, Serial1/0
O IA    10.1.23.0/30 [110/129532] via 10.1.245.2, 00:43:29, Serial1/0
O IA    10.55.30.1/32 [110/129533] via 10.1.245.2, 00:43:29, Serial1/0
O IA    10.44.4.0/22 [110/64767] via 10.1.245.4, 00:00:57, Serial1/0
O IA    10.45.1.0/24 [110/65766] via 10.1.245.4, 00:43:29, Serial1/0
O IA    10.1.45.0/30 [110/129532] via 10.1.245.5, 00:43:29, Serial1/0
O IA    10.55.20.1/32 [110/64767] via 10.1.245.2, 00:43:29, Serial1/0
C       10.55.10.0/24 is directly connected, Loopback0
C       10.1.245.0/29 is directly connected, Serial1/0
R1#