【Lab Objectives】
1. Learn LSA funtion of type1, type2, type3, type 4 and type5.
2. Learn OSPF Stub area features
3. Learn OSPF Stub area configuration methods
4. Learn OSPF Stub area configuration requirements: Stub area has at least one ABR, but no ASBR
【Lab Topology】
【Lab Steps】
1. Configure IP addresses of every router, and use ping command to confirm the direct interface connectivity of every router.
2. Configure OSPF and RIP protocol, and use ping and show ip route command to confirm that protocol can work normally
3. Configure redistribution on R3 to complete lab requirements. Configure as follows:
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R3(config)#router ospf 1 R3(config-router)#redistribute rip subnets metric 200 R3(config-router)#exit R3(config)# R3(config)#router rip R3(config-router)#redistribute ospf 1 metric 10 R3(config-router)#exit R3(config)#exit |
4. Check routing table of R1.
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R1#show ip route
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks C 172.16.255.0/30 is directly connected, Serial1/1 O IA 172.16.255.4/30 [110/128] via 172.16.255.2, 00:07:32, Serial1/1 O IA 172.16.255.8/30 [110/192] via 172.16.255.2, 00:06:57, Serial1/1 C 172.16.1.0/24 is directly connected, Loopback0 O IA 172.16.2.0/24 [110/193] via 172.16.255.2, 00:06:05, Serial1/1 O E2 10.0.0.0/8 [110/200] via 172.16.255.2, 00:02:01, Serial1/1 O E2 192.168.1.0/24 [110/200] via 172.16.255.2, 00:02:01, Serial1/1 R1# R1#ping 10.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 672/788/984 ms R1# |
5. Check link status database of R1
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R1#show ip ospf database
OSPF Router with ID (172.16.1.1) (Process ID 1)
Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 172.16.1.1 172.16.1.1 682 0x80000003 0x003BE1 3 172.16.255.5 172.16.255.5 677 0x80000003 0x0035B1 2
Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 172.16.2.0 172.16.255.5 581 0x80000001 0x004CEE 172.16.255.4 172.16.255.5 668 0x80000001 0x009BE1 172.16.255.8 172.16.255.5 633 0x80000001 0x00F543
Summary ASB Link States (Area 1) Link ID ADV Router Age Seq# Checksum 192.168.1.1 172.16.255.5 342 0x80000001 0x008648
Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 10.0.0.0 192.168.1.1 348 0x80000001 0x005B1B 0 192.168.1.0 192.168.1.1 348 0x80000001 0x0021F4 0 R1# |
6. We notice that R1 has learnt all the routes in this lab, but R1 need not to learn all the network routes. Too much route entries will enlarge the size of router, not using route query or network convergence. OSPF network routes are broadcasted through LSA. We may limit LSA blooding area and use proper summary routes, thus reduce the size of routing table, make it easy for network convergence, and strengthen network stability.
7. Configure area 1 as stub area on R1 and R2.
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R1(config)#router ospf 1 R1(config-router)#area 1 stub R1(config-router)#exit R1(config)#exit |
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R2(config)#router ospf 1 R2(config-router)#area 1 stub R2(config-router)#exit R2(config)# |
8. check again link status database of R1.
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R1#show ip ospf database
OSPF Router with ID (172.16.1.1) (Process ID 1)
Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 172.16.1.1 172.16.1.1 155 0x80000005 0x0055C7 3 172.16.255.5 172.16.255.5 155 0x80000005 0x004F97 2
Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 172.16.255.5 168 0x80000001 0x00017B 172.16.2.0 172.16.255.5 168 0x80000002 0x0068D3 172.16.255.4 172.16.255.5 168 0x80000002 0x00B7C6 172.16.255.8 172.16.255.5 168 0x80000002 0x001228 R1# |
By checking R1 database we find that LSA of type4 and type5 is refused, thus limit LSA flooding area.
9. Check routing table of R1, and confirm the changes of routing table. With the default route sent by R2, R1 need not to receive LSA of type3, i.e. need not to know ASBR location.
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R1#show ip route
Gateway of last resort is 172.16.255.2 to network 0.0.0.0
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks C 172.16.255.0/30 is directly connected, Serial1/1 O IA 172.16.255.4/30 [110/128] via 172.16.255.2, 00:04:19, Serial1/1 O IA 172.16.255.8/30 [110/192] via 172.16.255.2, 00:04:19, Serial1/1 C 172.16.1.0/24 is directly connected, Loopback0 O IA 172.16.2.0/24 [110/193] via 172.16.255.2, 00:04:19, Serial1/1 O*IA 0.0.0.0/0 [110/65] via 172.16.255.2, 00:04:19, Serial1/1 R1# |
10. Use ping command to confirm route efficiency
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R1#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 240/393/684 ms R1# |
11. From the above configuration, we have to learn that: stub area refused LSA of type4 and type5.
12. Lab finished.
Hope to helpful for you!
