On this post, I will be creating another lecture notes that can possible replaced the summarizations for Type 3 LSA ( or Summary LSA) or Type 5 LSA ( or AS External LSA). This would be the lazy method of summarizing both types of LSA.
SINGAPORE#ping 10.10.11.1 source 30.30.30.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.11.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 76/93/120 ms
Concept:
Laboratory Objective:
1. To understand that default route could be used on ASBR or Autonomous System Border Router instead of redistributing the prefixes as connected subnets.
2. To enable default route on the ASBR with the command “default-information originate always” .
3. To verify that default routes LSDB are classified as Type 5 LSA.
4. To verify that default routes could be advertise on different OSPF areas.
5. To verify the connectivity towards the prefixes that are not advertise from ASBR.
Here will be my topology for my laboratory on default route.
Here are my router configurations:
MANILA Router:
R1#config t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#hostname MANILA
MANILA(config)#int s3/0
MANILA(config-if)#ip add 192.168.12.1 255.255.255.0
MANILA(config-if)#no shut
MANILA(config-if)#exit
MANILA(config)#int lo0
MANILA(config-if)#ip add 10.10.10.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo1
MANILA(config-if)#ip add 10.10.11.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo2
MANILA(config-if)#ip add 10.10.12.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo3
MANILA(config-if)#ip address 10.10.13.1 255.255.255.0
MANILA(config-if)#exit
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#hostname MANILA
MANILA(config)#int s3/0
MANILA(config-if)#ip add 192.168.12.1 255.255.255.0
MANILA(config-if)#no shut
MANILA(config-if)#exit
MANILA(config)#int lo0
MANILA(config-if)#ip add 10.10.10.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo1
MANILA(config-if)#ip add 10.10.11.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo2
MANILA(config-if)#ip add 10.10.12.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#int lo3
MANILA(config-if)#ip address 10.10.13.1 255.255.255.0
MANILA(config-if)#exit
MANILA(config)#router ospf 1
MANILA(config-router)#network 192.168.12.0 0.0.0.255 area 0
MANILA(config-router)#default-information originate always <<< This is the key command to enable default route on OSPF.
MANILA(config-router)#^Z
MANILA(config-router)#default-information originate always <<< This is the key command to enable default route on OSPF.
MANILA(config-router)#^Z
MELBOURNE Router:
R2#config t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#hostname MELBOURNE
MELBOURNE(config)#int s3/0
MELBOURNE(config-if)#ip address 192.168.12.2 255.255.255.0
MELBOURNE(config-if)#no shut
MELBOURNE(config-if)#exit
MELBOURNE(config)#int s3/1
MELBOURNE(config-if)#ip address 192.168.23.2 255.255.255.0
MELBOURNE(config-if)#no shut
MELBOURNE(config-if)#exit
MELBOURNE(config)#int lo2
MELBOURNE(config-if)#ip address 20.20.20.1 255.255.255.0
MELBOURNE(config-if)#exit
MELBOURNE(config)#router ospf 1
MELBOURNE(config-router)#network 192.168.12.0 0.0.0.255 area 0
MELBOURNE(config-router)#network 192.168.12.0 0.0.0.255 area 0
MELBOURNE(config-router)#network 192.168.23.0 0.0.0.255 area 1
MELBOURNE(config-router)#^Z
MELBOURNE#
SINGAPORE Router:
R3#config t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#hostname SINGAPORE
SINGAPORE(config)#int s3/1
SINGAPORE(config-if)#ip address 192.168.23.3 255.255.255.0
SINGAPORE(config-if)#no shut
SINGAPORE(config-if)#exit
SINGAPORE(config)#int lo3
SINGAPORE(config-if)#ip address 30.30.30.1 255.255.255.0
SINGAPORE(config-if)#exit
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#hostname SINGAPORE
SINGAPORE(config)#int s3/1
SINGAPORE(config-if)#ip address 192.168.23.3 255.255.255.0
SINGAPORE(config-if)#no shut
SINGAPORE(config-if)#exit
SINGAPORE(config)#int lo3
SINGAPORE(config-if)#ip address 30.30.30.1 255.255.255.0
SINGAPORE(config-if)#exit
SINGAPORE(config)#router ospf 1
SINGAPORE(config-router)#network 30.30.30.0 0.0.0.255 area 1
SINGAPORE(config-router)#network 192.168.23.0 0.0.0.255 area 1
SINGAPORE(config-router)#^Z
SINGAPORE(config-router)#network 30.30.30.0 0.0.0.255 area 1
SINGAPORE(config-router)#network 192.168.23.0 0.0.0.255 area 1
SINGAPORE(config-router)#^Z
VERIFICATIONS:
A. Let’s check the OSPF database on MELBOURNE and SINGAPORE routers.
MELBOURNE#show ip ospf database
OSPF Router with ID (20.20.20.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
10.10.13.1 10.10.13.1 137 0x80000003 0x00E64C 2
20.20.20.1 20.20.20.1 1801 0x80000004 0x00F521 2
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
30.30.30.1 20.20.20.1 1801 0x80000002 0x00E57C
192.168.23.0 20.20.20.1 1801 0x80000002 0x0072CB
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
20.20.20.1 20.20.20.1 1801 0x80000002 0x003891 2
30.30.30.1 30.30.30.1 1703 0x80000004 0x0073C9 3
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
192.168.12.0 20.20.20.1 1801 0x80000002 0x00EB5D
Summary ASB Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
10.10.13.1 20.20.20.1 1801 0x80000002 0x007F1C
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 10.10.13.1 137 0x80000003 0x002B63 1
MELBOURNE#
>>> There were two important information which we can extract from the output above,
1. The ASBR (which is the MANILA router) were stored on LSDB of MELBOURNE router and is
reachable via MLEBOURNE router (20.20.20.1). As we know, this is called Type 4 LSA or
Summary ASBR LSA.
reachable via MLEBOURNE router (20.20.20.1). As we know, this is called Type 4 LSA or
Summary ASBR LSA.
2. The default route were recorded in as Type 5 AS External LSA’s as it is a Defaul Route. We
have to remember that Default Routes are classified under this LSA Type.
have to remember that Default Routes are classified under this LSA Type.
Now, let’s check the LSDB of SINGAPORE Router,
SINGAPORE#show ip ospf database
OSPF Router with ID (30.30.30.1) (Process ID 1)
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
20.20.20.1 20.20.20.1 227 0x80000003 0x003692 2
30.30.30.1 30.30.30.1 114 0x80000005 0x0071CA 3
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
192.168.12.0 20.20.20.1 227 0x80000003 0x00E95E
Summary ASB Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
10.10.13.1 20.20.20.1 227 0x80000003 0x007D1D
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 10.10.13.1 553 0x80000003 0x002B63 1
SINGAPORE#
>>> Similarly, we can see the same Sequence Number (0x80000003) for the LSU sent by MELBOURNE to SINGAPORE router. Link ID for the default route is 0.0.0.0 and is being advertise by 10.10.13.1 which is the MANILA router’s highest loopback interface (which will be the Router ID of MANILA). We can simply verify this with the “show ip ospf interface” command.
MANILA#show ip ospf interface s3/0 <<<< This is the OSPF interface facing MELBOURNE Router
Serial3/0 is up, line protocol is up
Internet Address 192.168.12.1/24, Area 0, Attached via Network Statement
Process ID 1, Router ID 10.10.13.1, Network Type POINT_TO_POINT, Cost: 64
Topology-MTID Cost Disabled Shutdown Topology Name
0 64 no no Base
>>> Similarly, we can see the LSA Type 4 ( or the ASBR Summary LSA). This LSA is telling the Singapore router how to reach the ASBR router ( MANILA Router).
B. Let’s check the routing table of the MELBOURNE & SINGAPORE Routers.
MELBOURNE#show ip route ospf
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 192.168.12.1 to network 0.0.0.0
O*E2 0.0.0.0/0 [110/1] via 192.168.12.1, 01:16:30, Serial3/0
30.0.0.0/32 is subnetted, 1 subnets
O 30.30.30.1 [110/65] via 192.168.23.3, 01:14:56, Serial3/1
MELBOURNE#
>> So as we have seen above, the default route were installed on the routing table as OSPF EXTERNAL TYPE 2 routes or O *E2. The * means it’s a candidate default route or simply a default route.
As we can see below, we have the same routing entries for the default routes except that we have an additional of Inter-Area Routes ( O IA) for the network 192.168.12.0/24 which is on Area 0. I think we’re going good.
SINGAPORE# show ip route ospf
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
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 192.168.23.2 to network 0.0.0.0
O*E2 0.0.0.0/0 [110/1] via 192.168.23.2, 01:19:48, Serial3/1
O IA 192.168.12.0/24 [110/128] via 192.168.23.2, 01:19:48, Serial3/1
SINGAPORE#
Obcourse MANILA Router will only received the Inter-Area Routes from Area 1 as per my topology.
MANILA#show ip route ospf
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
30.0.0.0/32 is subnetted, 1 subnets
O IA 30.30.30.1 [110/129] via 192.168.12.2, 01:21:13, Serial3/0
O IA 192.168.23.0/24 [110/128] via 192.168.12.2, 01:22:36, Serial3/0
MANILA#
C. Now, let’s verify the connectivity between MANILA and SINGAPORE network.
I have 4 Loopback interfaces on MANILA and as we know, we did NOT advertise them under OSPF or did the redistribution into the OSPF.
MANILA#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES unset administratively down down
FastEthernet1/0 unassigned YES unset administratively down down
FastEthernet2/0 unassigned YES unset administratively down down
FastEthernet2/1 unassigned YES unset administratively down down
Serial3/0 192.168.12.1 YES manual up up
Serial3/1 unassigned YES unset administratively down down
Serial3/2 unassigned YES unset administratively down down
Serial3/3 unassigned YES unset administratively down down
Loopback0 10.10.10.1 YES manual up up
Loopback1 10.10.11.1 YES manual up up
Loopback2 10.10.12.1 YES manual up up
Loopback3 10.10.13.1 YES manual up up
MANILA#sh run | sec ospf
router ospf 1
network 192.168.12.0 0.0.0.255 area 0
default-information originate always
MANILA#
I will run a ping towards the Loopback interfaces of MANILA router from SINGAPORE router to test the connectivity.
SINGAPORE#ping 10.10.10.1 source 30.30.30.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 76/99/116 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 76/99/116 ms
SINGAPORE#ping 10.10.11.1 source 30.30.30.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.11.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 76/93/120 ms
SINGAPORE#ping 10.10.12.1 source 30.30.30.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.12.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 88/97/112 ms
SINGAPORE#ping 10.10.13.1 source 30.30.30.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.13.1, timeout is 2 seconds:
Packet sent with a source address of 30.30.30.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 88/98/108 ms
SINGAPORE#traceroute 10.10.10.1
Type escape sequence to abort.
Tracing the route to 10.10.10.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.23.2 100 msec 84 msec 80 msec
2 192.168.12.1 108 msec 96 msec 96 msec
SINGAPORE#
NETWORK LESSON 
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