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Media OSPF Lab

Lab Topology

History

Did you know, the OSPF algorithm is considered a link-state protocol, based on the Dijkstra Shortest Path Algorithm? It is a common protocol used in a number of widely deployed environments in various industries.

Info

This lab has been limited to the following devices: s1-Spine1, s1-Spine2, s1-Leaf1, s1-Leaf4, s1-Host1, and s1-Host2. Additional devices on this topology are out of scope for this lab.

Preparing The Lab

  1. Log into the LabAccess jumpserver:
    1. Type labs at the Main Menu prompt. This will bring up additional lab menu selections.
    2. Type media-labs at this prompt to open the media lab section.
    3. Type media-ospf at this prompt and wait for the process to run.
    4. The script will configure the topology with the exception of s1-Leaf4.

Verification

On s1-Spine2, verify OSPF operation (which should not be operating correctly) with the following commands:

Command

show ip ospf neighbor

Expected Output

s1-spine2#show ip ospf neighbor
Neighbor ID     VRF      Pri State                  Dead Time   Address         Interface
10.127.255.2    default  1   FULL/BDR               00:00:35    10.127.23.2     Ethernet1

Command

show ip ospf interface

Expected Output

s1-spine2#show ip ospf interface
Loopback0 is up
  Interface Address 10.127.255.3/32, VRF default, Area 0.0.0.0
  Network Type Broadcast, Cost: 10
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router is 10.127.255.3
  No Backup Designated Router on this network
  Timer intervals configured, Hello 10, Dead 40, Retransmit 5
  Neighbor Count is 0 (Passive Interface)
  No authentication
Ethernet5 is up
  Interface Address 10.127.34.3/24, VRF default, Area 0.0.0.0
  Network Type Broadcast, Cost: 10
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router is 10.127.255.3
  No Backup Designated Router on this network
  Timer intervals configured, Hello 10, Dead 40, Retransmit 5
  Neighbor Count is 0
  No authentication
Ethernet1 is up
  Interface Address 10.127.23.3/24, VRF default, Area 0.0.0.0
  Network Type Broadcast, Cost: 10
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router is 10.127.255.3
  Backup Designated Router is 10.127.255.2
  Timer intervals configured, Hello 10, Dead 40, Retransmit 5
  Neighbor Count is 1
  No authentication

Command

show ip ospf database

Expected Output

s1-spine2#show ip ospf database

            OSPF Router with ID(10.127.255.3) (Process ID 100) (VRF default)


                 Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum Link count
10.127.255.2    10.127.255.2    344         0x80000007   0x5d3    3
10.127.255.1    10.127.255.1    346         0x80000006   0x2433   3
10.127.255.3    10.127.255.3    343         0x80000006   0xbe99   3

                 Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum
10.127.23.3     10.127.255.3    343         0x80000001   0x836e
10.127.12.2     10.127.255.2    344         0x80000001   0xf40c

Command

show ip route

Expected Output

spine2#show ip route

VRF: default
Codes: C - connected, S - static, K - kernel,
       O - OSPF, IA - OSPF inter area, E1 - OSPF external type 1,
       E2 - OSPF external type 2, N1 - OSPF NSSA external type 1,
       N2 - OSPF NSSA external type2, B I - iBGP, B E - eBGP,
       R - RIP, I L1 - IS-IS level 1, I L2 - IS-IS level 2,
       O3 - OSPFv3, A B - BGP Aggregate, A O - OSPF Summary,
       NG - Nexthop Group Static Route, V - VXLAN Control Service,
       DH - DHCP client installed default route, M - Martian,
       DP - Dynamic Policy Route

Gateway of last resort:
 S      0.0.0.0/0 [1/0] via 192.168.0.254, Management0

 O      10.127.12.0/24 [110/20] via 10.127.23.2, Ethernet1
 C      10.127.23.0/24 is directly connected, Ethernet1
 C      10.127.34.0/24 is directly connected, Ethernet5
 O      10.127.255.1/32 [110/30] via 10.127.23.2, Ethernet1
 O      10.127.255.2/32 [110/20] via 10.127.23.2, Ethernet1
 C      10.127.255.3/32 is directly connected, Loopback0
 O      172.16.15.0/24 [110/30] via 10.127.23.2, Ethernet1
 C      192.168.0.0/24 is directly connected, Management0
Note

All the route entries with a preceding “O” were learned via OSPF on s1-Spine2.

Lab Tasks

Configure OSPF

Configure OSPF on the s1-Leaf4 switch using the following steps.

  1. Configure the Ethernet3, Ethernet4, and Loopback0 interfaces as well as OSPF on s1-Leaf4 to be used for OSPF adjacency formation with adjacent devices (s1-Spine 2 in this case):

    Commands

    configure
interface loopback 0
    ip address 10.127.255.4/32
interface ethernet 3
    no switchport
    ip address 10.127.34.4/24
interface ethernet 4
    no switchport
    ip address 172.16.46.4/24
router ospf 100
    router-id 10.127.255.4

    Example

    s1-leaf4#configure
s1-leaf4(config)#int ethernet 3
s1-leaf4(config-if-Et3)#no switchport
s1-leaf4(config-if-Et3)#ip address 10.127.34.4/24
s1-leaf4(config)#int ethernet 4
s1-leaf4(config-if-Et4)#no switchport
s1-leaf4(config-if-Et4)#ip address 172.16.46.4/24
s1-leaf4(config)#int loopback 0
s1-leaf4(config-if-Lo0)#ip address 10.127.255.4/32
s1-leaf4(config)#router ospf 100
s1-leaf4(config-router-ospf)#router-id 10.127.255.4
    Info

    All interfaces are point-to-point connections for this lab, none are trunk or access ports.

  2. Specify the network statement which encompasses all the interfaces that will take part in the OSPF process:

    Commands

    configure
router ospf 100
    network 10.127.0.0/16 area 0.0.0.0
    network 172.16.46.0/24 area 0.0.0.0

    Example

    s1-leaf4(config)#configure
s1-leaf4(config)#router ospf 100
s1-leaf4(config-router-ospf)#network 10.127.0.0/16 area 0.0.0.0
s1-leaf4(config-router-ospf)#network 172.16.46.0/24 area 0.0.0.0
    Info

    All interfaces which fall into the range of the network statement will take part in the OSPF process and exchange hello packets.

  3. Certain interfaces do not need to take part in the OSPF process, but we still want the IP’s or networks to be included in the routing domain. This is where we leverage the “passive-interface” command to allow this. These interfaces will be associated to the area in which the network statement is configured.

    Commands

    configure
router ospf 100
    passive-interface loopback0
    passive-interface ethernet4

    Example

    s1-leaf4(config)#router ospf 100
s1-leaf4(config-router-ospf)#passive-interface loopback 0
s1-leaf4(config-router-ospf)#passive-interface ethernet4

Test

Validate the OSPF routing domain and end to end reachability.

  1. Confirm the OSPF adjacency has been established and the routing table on s1-Leaf4 has been populated with the appropriate entries:

    Command

    show ip ospf neighbor

    Expected Output

    s1-leaf4(config-if-Et4)#show ip ospf neighbor
Neighbor ID     VRF      Pri State                  Dead Time   Address         Interface
10.127.255.3    default  1   FULL/DR                00:00:31    10.127.34.3     Ethernet3

    Command

    show ip ospf interface

    Expected Output

    s1-leaf4(config-if-Et4)#show ip ospf interface
Loopback0 is up
    Interface Address 10.127.255.4/32, VRF default, Area 0.0.0.0
    Network Type Broadcast, Cost: 10
    Transmit Delay is 1 sec, State DR, Priority 1
    Designated Router is 10.127.255.4
    No Backup Designated Router on this network
    Timer intervals configured, Hello 10, Dead 40, Retransmit 5
    Neighbor Count is 0 (Passive Interface)
    No authentication
Ethernet3 is up
    Interface Address 10.127.34.4/24, VRF default, Area 0.0.0.0
    Network Type Broadcast, Cost: 10
    Transmit Delay is 1 sec, State Backup DR, Priority 1
    Designated Router is 10.127.255.3
    Backup Designated Router is 10.127.255.4
    Timer intervals configured, Hello 10, Dead 40, Retransmit 5
    Neighbor Count is 1
    No authentication
Ethernet4 is up
    Interface Address 172.16.46.4/24, VRF default, Area 0.0.0.0
    Network Type Broadcast, Cost: 10
    Transmit Delay is 1 sec, State DR, Priority 1
    Designated Router is 10.127.255.4
    No Backup Designated Router on this network
    Timer intervals configured, Hello 10, Dead 40, Retransmit 5
    Neighbor Count is 0
    No authentication

    Command

    show ip ospf database

    Expected Output

    s1-leaf4(config-if-Et4)#sh ip ospf database

        OSPF Router with ID(10.127.255.4) (Process ID 100) (VRF default)


             Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum Link count
10.127.255.1    10.127.255.1    863         0x80000009   0x1e36   3
10.127.255.2    10.127.255.2    861         0x8000000a   0xfed6   3
10.127.255.4    10.127.255.4    339         0x80000007   0xde1f   3
10.127.255.3    10.127.255.3    1181        0x80000009   0x5e46   3

                Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum
10.127.23.3     10.127.255.3    860         0x80000004   0x7d71
10.127.34.3     10.127.255.3    1181        0x80000001   0x26be
10.127.12.2     10.127.255.2    861         0x80000004   0xee0f

    Command

    show ip route

    Expected Output

    s1-leaf4(config-if-Et4)#sh ip route

VRF: default
Codes: C - connected, S - static, K - kernel,
    O - OSPF, IA - OSPF inter area, E1 - OSPF external type 1,
    E2 - OSPF external type 2, N1 - OSPF NSSA external type 1,
    N2 - OSPF NSSA external type2, B I - iBGP, B E - eBGP,
    R - RIP, I L1 - IS-IS level 1, I L2 - IS-IS level 2,
    O3 - OSPFv3, A B - BGP Aggregate, A O - OSPF Summary,
    NG - Nexthop Group Static Route, V - VXLAN Control Service,
    DH - DHCP client installed default route, M - Martian,
    DP - Dynamic Policy Route

Gateway of last resort:
S      0.0.0.0/0 [1/0] via 192.168.0.254, Management0

O      10.127.12.0/24 [110/30] via 10.127.34.3, Ethernet3
O      10.127.23.0/24 [110/20] via 10.127.34.3, Ethernet3
C      10.127.34.0/24 is directly connected, Ethernet3
O      10.127.255.1/32 [110/40] via 10.127.34.3, Ethernet3
O      10.127.255.2/32 [110/30] via 10.127.34.3, Ethernet3
O      10.127.255.3/32 [110/20] via 10.127.34.3, Ethernet3
C      10.127.255.4/32 is directly connected, Loopback0
O      172.16.15.0/24 [110/40] via 10.127.34.3, Ethernet3
C      172.16.46.0/24 is directly connected, Ethernet4
C      192.168.0.0/24 is directly connected, Management0

  2. Validate end-to-end connectivity by logging into s1-Host2 and verifying connectivity with s1-Host1:

    Command

    ping 172.16.15.5

    Expected Output

    s1-host2# ping 172.16.15.5
PING 172.16.15.5 (172.16.15.5) 72(100) bytes of data.
80 bytes from 172.16.15.5: icmp_seq=1 ttl=60 time=99.5 ms
80 bytes from 172.16.15.5: icmp_seq=2 ttl=60 time=102 ms
80 bytes from 172.16.15.5: icmp_seq=3 ttl=60 time=165 ms
80 bytes from 172.16.15.5: icmp_seq=4 ttl=60 time=161 ms
80 bytes from 172.16.15.5: icmp_seq=5 ttl=60 time=158 ms

--- 172.16.15.5 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 40ms
rtt min/avg/max/mdev = 99.508/137.682/165.494/29.858 ms, pipe 5, ipg/ewma 10.149/120.314 ms
Success

If OSPF has been configured correctly and the routing table on s1-Leaf4 has converged, then s1-Host1 should be reachable from s1-Host2!

Test your knowledge

When inspecting the routing table on s1-Leaf4, why are all the infrastructure IP address in there? What are the positive and negative results of that?

Tip

The following additional commands are useful to verify connectivity for validation and troubleshooting purposes:

  • show ip ospf neighbor
  • show ip ospf interface
  • show ip ospf database
  • show ip route