0. CCNA Exam Questions

Why do we need OSPF?
- Ans: 2 reasons: To enter other networks, to resolve non-directly connected network

10. Dynamic Roututing

10.3 OSPF

10.3.6 Interface and OSPF network types

	Ethernet interfaces (e.g. f0/0, g0/0, …)	Serial Interfaces (e.g. s0/0/0)
Commonly used in	LAN/WAN	Usually WAN (leased line)
Layer 2 protocols(s)	Ethernet	HDLC/ PPP (Both are out syll)
Default OSPF Network type (Default is changable)	Broadcast	Point-to-point

2 ways of configuring OSPF network:

10.3.7 OSPF Versioning

Under format RFC2328, most OSPF is version 2 (v2). But version 2 only supports IPv4. This tech is from the late 90s
If we have OSPF version 3 (v3) (specified in RFC5340) will support IPv6.

10.4 Configuring OSPF Broadcast on Cicso Router

Let’s look at the topology:
Note: OSPF Area 0 is the backbone, only a single area.
Recall how to determine BR and BDR:
- step 1: OSPF pirority 0 / 1
- step 2: OSPF Highest Router ID
Recall how to determine Router ID:
- No pre-set router id, verify with do sh run
- No loopback int on g0/1, g0/0
- highest physical IP: Router 1 = 192.168.1.1
Router 1 setup ```bash en conf t hostname Router1

int g0/1 ip address 10.0.0.1 255.0.0.0 no shut

int g0/0 ip address 192.168.1.1 255.255.255.0 no shut

end

- Router 2 setup (Please note OSPF number is unique to it's own device. Different regions don't interfere w/ each other.)
```bash
en
conf t
hostname Router2

int g0/1
ip address 172.16.0.2 255.255.0.0
no shut

int g0/0
ip address 192.168.1.2 255.255.255.0
no shut

end

Router 2 ``` conf t router ospf 1 network 192.168.1.0 0.0.0.255 area 0 network 172.16.0.0 0.0.255.255 area 0

```

Note 1: ospf # must specify a number, but this number can be user defined/ random
Note 2: Defining g0/1 so it can broadcast to other networks
The end goal is this:
Code explaination:
- router ospf 1 = turns on ospf w/ process number 1 (For CISCO IOS the range must be 1-65535)

SIMULATION 3: LAB

Topology Diagram:
We have a set of tasks and instructions…
- Instructions:
  - OSPF and IP connections are pre-configured
  - Do not change IP and Do not change OSPF
  - For this setup, all next hops and connected interfaces are used to configure static routes
  - only exceptions are for load balancing or redudancy without floating static
  - Connection must be established between subnet 172.20.20.128/25 & LAN at 192.168.0.0/24 (Basically LAN and Internet needs to be connected)
- Tasks:
  - Task 1: Connect SW1 LAN subnet in R2 (Router2)
    - Solution: make a static route
    - Recall: ip route <destination network> <network masking> <gateway address>/<outgoing address>
    - That outgoing address = next-hop-IP-to-SW1 : “Replace next-hop-IP-to-SW1” with the IP address of the interface on R2 that connects to SW1, or the IP of SW1 itself if it’s Layer 3 capable.
    - en conf t ip route 192.168.0.0 255.255.255.0 10.10.31.1 copy run start
    - Destination network for LAN is 192.168.0.0 since for E0/1 it’s 192.168.0.1 (with a dot 1 notation)
    - Network masking is /24: hence it’s 255.255.255.0
    - outgoing address (on switch side?): we’re leaving through E0/0 without a doubt from R2. Hence the ip should be 10.10.31.1
  - Task 2: Connect Internet subnet to R1 Router
    - Solution: Setting default route and default gateway
    - Recall: 0.0.0.0 0.0.0.0 = default route. 10.10.13.3 = default gateway
    - Do these on R1
      en conf t ip route 0.0.0.0 0.0.0.0 10.10.13.3 copy run start
    - 10.10.13.3 = default gateway since 10.10.13.0 is what R1 sees and .3 is the notation R2 receives
  - Task 3: Make a single static route in R2 to Internet subnet. Factor in redudancy links between R1 and R2. R2 default route is NOT ALLOWED.
    - Solution: First check OSPF and setup static route
    - Recall: sh ip route to view a partial routing table
    - Do these on R2
      en sh ip route
    o 10.10.1.1/32 [110/11] via 10.10.12.129, 00:43:32, Ethernet0/2 [110/11] via 10.10.12.1, 00:43:32, Ethernet 0/1
    Means that an OSPF to 10.10.1.1/32 load balancing w/ outgoing interfaces E0/2 and E0/1 already exist in R2 routing table
    conf t ip route 172.20.20.128 255.255.255.128 10.10.1.1 ??? end copy run start
    or ip route 172.20.20.128 255.255.255.128 e0/2 and ip route 172.20.20.128 255.255.255.128 e0/1s
  - Task 4: Make a static route in R1 to Switch LAN subnet. Primary link must be E0/1, backup link must be E0/2 via floating route. Change AD/ Administractive distance if needed.
    - Solution: Check ip route and setup AD route, no need to set floating static route
    - Recall:
    - Do these on R1
      en sh ip route
    o 192.168.0.0/24 [110/20] via 10.10.12.130, 00:01:08, Ethernet0/2
    conf t ip route 192.168.0.0 255.255.255.0 10.10.12.2 end copy run start
    or maybe ip route 192.168.0.0 255.255.255.0 e0/1

SIMULATION 15: LAB

Topology Diagram:
Description:
- Physical Cables are in place
- R4 and C1 are fully configured and cannot be accessed
- R4 LAN interface use .4 in last octet for each subnet
- Need to establish connection e2e
Tasks:
- Task 1: Setup static routing to ensure R1 piroritize path to R2 to reach only PC1 on R4’s LAN
  - Ans: PC1 is the host route. Do these on R1, then on R2
  - Note: 10.0.41.10 is the computer IP
    en conf t ip route 10.0.41.10 255.255.255.255 e0/0 end copy run start
```
  en
  conf t
  ip route 10.0.41.10 255.255.255.255 10.0.24.4
  end
  copy run start
```
- Task 2: Setup static routing to ensure R1 traffic will take another path through R3 to PC1 during outage
  - Answer: Do these on R1, then R3
    en conf t ip route 10.0.41.10 255.255.255.255 e0/1 2 end copy run start
  - The extra 2 at the end refers to AD = 2. Also this is the primary route
  - Answer: Do these on R1, then R3
    en conf t ip route 10.0.41.10 255.255.255.255 10.0.34.4 end copy run start
- Task 3: Setup default routes on R1 and R3 to internet while minimizing hops
  - Answer: Do these on R1, then R3
    en conf t ip route 0.0.0.0 0.0.0.0 e0/1 end copy run start
```
  en
  conf t
  ip route 0.0.0.0 0.0.0.0 209.165.201.1
  end
  copy run start
```

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