OSPF (open shortest path first) part iii
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The document provides a detailed configuration guide for OSPF (Open Shortest Path First) protocol across multiple routers, including configuration commands for interfaces and OSPF areas. It discusses the setup of stub areas, total stub areas, and Not-So-Stubby Areas (NSSAs), as well as the process of route redistribution between different OSPF and EIGRP domains. Additionally, it outlines the necessary steps for providing internet access and configuring NAT (Network Address Translation) on a specific router.
OSPF (open shortest path first) part iii
- 1. OSPF (Open Shortest Path First) Part- III Topology R1 (config) #int fa0/0 R1 (config-if) #ip add 192.168.101.1 255.255.255.0 R1 (config-if) #no shut R1 (config) #int s0/0 R1 (config-if) #ip add 192.168.1.1 255.255.255.0 R1 (config-if) #no shut R2 (config) #int fa0/0 R2 (config-if) #ip add 192.168.102.1 255.255.255.0 R2 (config-if) #no shut R2 (config) #int s0/0 R2 (config-if) #ip add 192.168.1.2 255.255.255.0 R2 (config-if) #no shut Figure 1 OSPF Topology
- 2. OSPF (Open Shortest Path First) Part- III R2 (config) #int s0/1 R2 (config-if) #ip add 192.168.2.1 255.255.255.0 R2 (config-if) #no shut R3 (config) #int f0/0 R3 (config-if) #ip add 192.168.103.1 255.255.255.0 R3 (config-if) #no shut R3 (config) #int s0/0 R3 (config-if) #ip add 192.168.2.2 255.255.255.0 R3 (config-if) #no shut R3 (config) #int s0/1 R3 (config-if) #ip add 192.168.3.1 255.255.255.0 R3 (config-if) #no shut R3 (config) #int s0/2 R3 (config-if) #ip add 192.168.6.1 255.255.255.0 R3 (config-if) #no shut R3 (config) #int s0/3 R3 (config-if) #ip add 101.1.1.100 255.255.255.0 R3 (config-if) #no shut R4 (config) #int fa0/0 R4 (config-if) #ip add 192.168.104.1 255.255.255.0 R4 (config-if) #no shut R4 (config) #int s0/0 R4 (config-if) #ip add 192.168.3.2 255.255.255.0 R4 (config-if) #no shut R4 (config) #int s0/1 R4 (config-if) #ip add 192.168.4.1 255.255.255.0 R4 (config-if) #no shut R5 (config) #int f0/0 R5 (config-if) #ip add 192.168.105.1 255.255.255.0 R5 (config-if) #no shut R5 (config) #int s0/0 R5 (config-if) #ip add 192.168.4.2 255.255.255.0 R5 (config-if) #no shut R5 (config) #int s0/1 R5 (config-if) #ip add 192.168.5.1 255.255.255.0 R5 (config-if) #no shut R6 (config) #int f0/0 R6 (config-if) #ip add 192.168.106.1 255.255.255.0
- 3. OSPF (Open Shortest Path First) Part- III R6 (config-if) #no shut R6 (config) #int s0/0 R6 (config-if) #ip add 192.168.5.2 255.255.255.0 R6 (config-if) #no shut R6 (config) #int loo 1 R6 (config-if) #ip add 172.60.1.1 255.255.255.0 R6 (config) #int loo 2 R6 (config-if) #ip add 172.60.2.1 255.255.255.0 R6 (config) #int loo 3 R6 (config-if) #ip add 172.60.3.1 255.255.255.0 R6 (config) #int loo 4 R6 (config-if) #ip add 172.60.4.1 255.255.255.0 R6 (config) #int loo 5 R6 (config-if) #ip add 172.60.5.1 255.255.255.0 R7 (config) #int fa0/0 R7 (config-if) #ip add 192.168.107.1 255.255.255.0 R7 (config-if) #no shut R7 (config) #int s0/0 R7 (config-if) #ip add 192.168.6.2 255.255.255.0 R7 (config-if) #no shut R7 (config) #int loo 1 R7 (config-if) #ip add 172.70.1.1 255.255.255.0 R7 (config) #int loo 2 R7 (config-if) #ip add 172.70.2.1 255.255.255.0 R7 (config) #int loo 3 R7 (config-if) #ip add 172.70.3.1 255.255.255.0 R7 (config) #int loo 4 R7 (config-if) #ip add 172.70.4.1 255.255.255.0 R7 (config) #int loo 5 R7 (config-if) #ip add 172.70.5.1 255.255.255.0 R7#ping 192.168.6.1 R7#ping 192.168.6.1 Successful ISP (config) #int fa0/0 ISP (config-if) #ip add 102.1.1.1 255.255.255.0 ISP (config-if) #no shut ISP (config) #int s0/0 ISP (config-if) #ip add 101.1.1.1 255.255.255.0
- 4. OSPF (Open Shortest Path First) Part- III ISP (config-if) #no shut OSPF Configuration R1 (config) #int fa0/0 R1 (config-if) #ip os 100 area 1 R1 (config) #int s0/0 R1 (config-if) #ip os 100 area 1 R2 (config) #int fa0/0 R2 (config-if) #ip os 100 area 1 R2 (config) #int s0/0 R2 (config-if) #ip os 100 area 1 R2 (config) #int s0/1 R2 (config-if) #ip os 100 area 0 R3 (config) #int fa0/0 R3 (config-if) #ip os 100 area 0 R3 (config) #int s0/0 R3 (config-if) #ip os 100 area 0 R3 (config) #int s0/1 R3 (config-if) #ip os 100 area 0 R3 (config-if) #router ei 100 R3 (config-router) #no auto-summary R3 (config-router) #network 192.168.6.0 R4 (config) #int fa0/0 R4 (config-if) #ip os 100 area 2 R4 (config) #int s0/0 R4 (config-if) #ip os 100 area 0 R4 (config) #int s0/1 R4 (config-if) #ip os 100 area 2 R5 (config) #int s0/0 R5 (config-if) #ip os 100 area 2 R5 (config-if) #router ei 200 R5 (config-router) #no auto-summary R5 (config-router) #network 192.168.105.0 R5 (config-router) #network 192.168.5.0 R6 (config-if) #router ei 200 R6 (config-router) #no auto-summary
- 5. OSPF (Open Shortest Path First) Part- III R6 (config-router) #network 0.0.0.0 R7 (config-if) #router ei 200 R7 (config-router) #no auto-summary R7 (config-router) #network 0.0.0.0 R3#sh ip route Now we want to communicate OSPF domain with ei 100 domain. For that we will perform here redistribution R3 (config) #router os 100 R3 (config-router) #redistribute ei 100 subnets metric-type 1 R3 (config-router) #router ei 100 R3 (config-router) #redistribute os 100 metric 1 1 1 1 1 We performed here two way of redistribution. R1#ping 172.70.1.1 source fa0/0 Successful R1#sh ip route os Here we can see two types of routes First is intra area (which belongs to its area) OIA means Inter area E – External Area Now our task is configure area 1 is as stub. R1 (config) #router os 100 R1 (config-router) #area 1 stub R2 (config) #router os 100 R2 (config-router) #area 1 stub Requirements for stub area 1. Virtual links are not allowed 2. Area 0 can’t be stub 3. All the routers must be agree that we are a part of stub area. If you are configuring R1, that area 1 is stub so it is your duty you have to configure R2 that area 1 is stub, if you will not configure, neighborship will not established.
- 6. OSPF (Open Shortest Path First) Part- III R1#sh ip route os R1#ping 172.70.1.1 source fa0/0 Successful R2 #sh ip route It contains entire ospf routes. Now we will see totally stub, it filters the external routes and inter area routes, and places them as a default route. R2 (config) #router os 100 R2 (config) #area 1 stub no-summary R1#sh ip route os We can see small routing table here R5#sh ip route os R5 (config) #router os 100 R5 (config-router) #area 2 stub R4 (config) #router os 100 R4 (config-router) #area 2 stub no-summary R5#sh ip route os R5#ping 192.168.101.1 source s0/0 successful Now we will perform redistribution on R5 R5 (config) #router os 100 R5 (config-router) #redistribute ei 200 subnets metric-type 1 R5 (config) #router ei 200 R5 (config-router) #redistribute os 100 metric 1 1 1 1 1 R3#sh ip route Here we cannot see 172.60.0.0 routes Now we will configure NSSA First we need to remove this command here R4 (config) #router os 100 R4 (config-router) #no area 2 stub
- 7. OSPF (Open Shortest Path First) Part- III R5 (config) #router os 100 R5 (config-router) #no area 2 stub If we will remove stub command totally stub command will removed automatically. R4 (config) #router os 100 R4 (config-router) #area 2 nssa R5 (config) #router os 100 R5 (config-router) #area 2 nssa R3#sh ip route Here we can see O E 1 – 172.60.1.0 to 5 R7#sh ip route ei Here we can see this route 172.60.1.0 to 5 R4#sh ip route os It contain 70 series here 172.70.0.0 R5#sh ip route os It doesn’t contain the route of 172.70.0.0 R5#ping 172.70.1.1 not successful Now we will configure Totally NSSA on R4 R4 (config) #router os 100 R4 (config-router) #area 2 nssa no-summary default-information-originate R5#ping 172.70.1.1 successful R6#ping 172.70.1.1 successful R6#ping 172.70.1.1 source fa0/0 successful
- 8. OSPF (Open Shortest Path First) Part- III Now we will remove stub and totally stub from area 1 R1 (config) #router os 100 R1 (config-router) #no area 1 stub R2 (config) #router os 100 R2 (config-router) #no area 1 stub Now here we will provide the internet access on all routers. R3 is directly connected with the ISP router. R3#ping 101.1.1.1 successful. R3#ping 102.1.1.1 not successful. Now we will create default route on R3 towards ISP R3 (config) #Ip route 0.0.0.0 0.0.0.0 101.1.1.1 R3#ping 102.1.1.1 successful R3#ping 101.1.1.1 successful Here R3 is able to communicate with the ISP R3#ping 102.1.1.1 source fa0/0 not successful. R3 (config) #int s0/0 R3 (config-if) #ip nat inside R3 (config-if-nat) #int s0/1 R3 (config-if) #ip nat inside R3 (config-if-nat) #int s0/2 R3 (config-if) #ip nat inside R3 (config-if-nat) #int s0/3 R3 (config-if) #ip nat outside R3 (config-if-nat) #int f0/0 R3 (config-if) #ip nat inside R3 (config) #access-list 10 permit any R3 (config-access) #ip nat inside source list 10 int s0/3 overload R3#ping 102.1.1.1 source fa0/0 successful R3#sh ip nat translation Now we will provide the internet access to all areas. R2#sh ip route It hasn’t any default route so it can’t communicate with the internet.
- 9. OSPF (Open Shortest Path First) Part- III R3 (config) #router os 100 R3 (config-router) #default-information originate always R2 #sh ip route Here we can see a default route O*E2 0.0.0.0/0 R1#piing 102.1.1.1 source fa0/0 successful R6#ping 102.1.1.1 source loo1 successful R7#ping 102.1.1.1 source loo1 not successful R7#sh ip route It doesn’t contain default route R3 (config) #ip summary-address ei 100 0.0.0.0 0.0.0.0 R3#sh ip route D* 0.0.0.0 / 0 Now we can see here default route. R7#ping 102.1.1.1 source loo 1 successful There are three ways to generate default route in Eigrp 1. Redistribution 2. Summarization 3. IP default network. Now here we will check LSAs. R1#sh ip ospf database Router LSA Router LSA contains router ID of a router. It is sent within an area. Router ID (i) Highest Loop Back (ii) Highest Up Physical int IP (iii) Router ID Here we can see two router ID
- 10. OSPF (Open Shortest Path First) Part- III 192.168.101.1 192.168.102.1 Network LSA It contains DR router ID and it is sent by DR. DR & BDR are elected only in Broadcast and non-broadcast multi-access network. We have point to point link, so DR and BDR is not available. We will make forcefully it broadcast segment via command. R1 (config) #int s0/0 R1 (config-if) #ip os network broadcast R2 (config) #int s0/0 R2 (config-if) #ip os network broadcast R1#sh ip os neighbor R1#debug ip os adj R1#clear ip os process Yes R1#un all We can see first is Down state. Attempt state only happens in frame-realy. To check init we need to go on R2. R2#debug ip os adj R2#clear ip process Yes R2#un all Here we can see init. Network LSA Contain DR ID For DR (i) Highest router Priority (ii) Highest router ID Router 2 is DR here.
- 11. OSPF (Open Shortest Path First) Part- III Summary LSA When a route of one area goes to another area they go as summary SLA. It is sent by ABR. Here R2 is ABR AS LSA It contains ASBR router ID & it is sent by ABR R3 is ASBR here External LSA It contains External routes. It is sent by ASBR. 172.70 series sending R3 172.60 series sending R4 Group Membership LSA – It is not supported by cisco. NSSA– It allows an ASBR to send external area through stub area to backbone area using LSA 7. R5#sh ip os database R4#sh ip os database R3#sh ip os database