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Layer 3 Leaf-Spine with OSPF

Lab Topology

Note

The manually entered commands that are part of this lab are equivalent to L3LS-OSPF_s1-leaf4_complete.

Preparing The Lab

  1. Log into the LabAccess jumpserver:

    1. Type l3ls-ospf at the Main Menu prompt.

      Info

      Did you know the l2ls script is composed of Python code that uses the CloudVision Portal REST API to automate the provisioning of CVP Configlets? The configlets that are configured via the REST API are L3LS-OSPF_s1-spine1, L3LS-OSPF_s1-spine2, L3LS-OSPF_s1-leaf1, L3LS-OSPF_s1-leaf2, L3LS-OSPF_s1-leaf3, and L3LS-OSPF_s1-leaf4.

    2. The script will pre-configure the topology with the exception of s1-Leaf4. The main task is to configure this device.

Lab Tasks

Note

Arista EOS utilizes an Industry-Standard CLI. When entering configuration commands, be sure to first type configure to enter configuration mode.

Configure VLAN SVI and vARP

  1. Create the vARP MAC Address in Global Configuration mode.

    Command

    ip virtual-router mac-address 00:1c:73:00:00:34

  2. Create the VLAN, SVI and the Virtual Router Address

    Commands

    vlan 134
   name Host_Network_134
!
interface vlan 134
   ip address 10.111.134.3/24
   ip virtual-router address 10.111.134.1

Verification

Verify the previously applied configuration with the following commands:

Command

show ip interface brief

Expected Output

s1-leaf4#show ip interface brief
                                                                               Address
Interface         IP Address            Status       Protocol           MTU    Owner
----------------- --------------------- ------------ -------------- ---------- -------
Management0       192.168.0.15/24       up           up                1500
Vlan134           10.111.134.3/24       up           up                1500
Vlan4094          10.255.255.2/30       up           up                1500

Command

show ip virtual-router

Expected Output

s1-leaf4#show ip virtual-router
IP virtual router is configured with MAC address: 001c.7300.0034
IP virtual router address subnet routes not enabled
MAC address advertisement interval: 30 seconds

Protocol: U - Up, D - Down, T - Testing, UN - Unknown
         NP - Not Present, LLD - Lower Layer Down

Interface       Vrf           Virtual IP Address       Protocol       State
--------------- ------------- ------------------------ -------------- ------
Vl134           default       10.111.134.1             U              active

Configure OSPF

  1. Based on the diagram, configure L3 interfaces on s1-leaf4 to s1-spine1/s1-spine2 and interface Loopback0

    Commands

    interface Ethernet2
   description L3 Uplink - s1-spine1
   no switchport
   ip address 10.111.1.7/31
!
interface Ethernet3
   description L3 Uplink - s1-spine2
   no switchport
   ip address 10.111.2.7/31
!
interface Loopback0
   description Management and Router-id
   ip address 10.111.254.4/32

  2. Validate the configuration with the following:

    Command

    show ip interface brief

    Expected Output

    s1-leaf4#show ip interface brief
                                                                              Address
Interface         IP Address            Status       Protocol            MTU    Owner
----------------- --------------------- ------------ -------------- ----------- -------
Ethernet2         10.111.1.7/31         up           up                 1500
Ethernet3         10.111.2.7/31         up           up                 1500
Loopback0         10.111.254.4/32       up           up                65535
Management0       192.168.0.15/24       up           up                 1500
Vlan134           10.111.134.3/24       up           up                 1500
Vlan4094          10.255.255.2/30       up           up                 1500

  3. Enable OSPF and configure the interfaces on s1-leaf4. Connections to s1-spine1/s1-spine2 and s1-leaf3 with be part of Area 0.

    Note

    In EOS, process-level configuration happens with the OSPF context and peer-specific configuration such as Area and Authentication happen under the interface.

    Commands

    interface Ethernet2
   ip ospf area 0.0.0.0
   ip ospf network point-to-point
!
interface Ethernet3
   ip ospf area 0.0.0.0
   ip ospf network point-to-point
!
interface Vlan4094
   ip ospf area 0.0.0.0
   ip ospf network point-to-point
!
router ospf 100
   router-id 10.111.254.4
    Note

    We are leveraging OSPF Point-to-Point networks to eliminate the need for DR elections on non-broadcast networks.

  4. Validate the configuration and process status.

    Command

    show active
    Note

    In EOS, the show active command shows the running-configuration of whatever configuration context you are currently in.

    Expected Output

    s1-leaf4(config-router-ospf)#show active
router ospf 100
   router-id 10.111.254.4
   max-lsa 12000

    Command

    show run interfaces Ethernet 2-3

    Expected Output

    s1-leaf4(config-router-ospf)#show run interfaces Ethernet 2-3
interface Ethernet2
   description L3 Uplink - s1-spine1
   no switchport
   ip address 10.111.1.7/31
   ip ospf area 0.0.0.0
   ip ospf network point-to-point
interface Ethernet3
   description L3 Uplink - s1-spine2
   no switchport
   ip address 10.111.2.7/31
   ip ospf area 0.0.0.0
   ip ospf network point-to-point

    Command

    show ip ospf summary

    Expected Output

    s1-leaf4(config-router-ospf)#show ip ospf summary
OSPF instance 100 with ID 10.111.254.4, VRF default
Time since last SPF: 122 s
Max LSAs: 12000, Total LSAs: 1
Type-5 Ext LSAs: 0
ID               Type   Intf   Nbrs (full) RTR LSA NW LSA  SUM LSA ASBR LSA TYPE-7 LSA
0.0.0.0          normal 3      0    (0   ) 1       0       0       0       0

  5. Enable OSPF Authentication on s1-leaf4 to peer to s1-spine1/s1-spine2 and s1-leaf3

    Commands

    interface Ethernet2
   ip ospf authentication message-digest
   ip ospf message-digest-key 1 sha512 Arista123!
!
interface Ethernet3
   ip ospf authentication message-digest
   ip ospf message-digest-key 1 sha512 Arista123!
!
interface Vlan4094
   ip ospf authentication message-digest
   ip ospf message-digest-key 1 sha512 Arista123!

  6. Verify that peering is established to directly connected neighbors.

    Command

    show ip ospf neighbor

    Expected Output

    s1-leaf4(config-if-Vl4094)#show ip ospf neighbor
Neighbor ID     Instance VRF      Pri State                  Dead Time   Address         Interface
10.111.0.1      100      default  0   FULL                   00:00:38    10.111.1.6      Ethernet2
10.111.0.2      100      default  0   FULL                   00:00:37    10.111.2.6      Ethernet3
10.111.254.3    100      default  1   FULL                   00:00:31    10.255.255.1    Vlan4094

  7. Enable OSPF Advertisement of local networks on s1-leaf4.

    Commands

    interface Loopback0
   ip ospf area 0.0.0.0
!
interface Vlan134
   ip ospf area 0.0.0.0

  8. However, we do not want to form OSPF adjacencies on these interfaces, so enable passive-interface functionality on s1-leaf4.

    Commands

    router ospf 100
   passive-interface default
   no passive-interface Ethernet2
   no passive-interface Ethernet3
   no passive-interface Vlan4094

OSPF Verification

  1. Check the OSPF Database and IP route tables on s1-leaf4 as well as each of the Spines and Leafs

    Command

    show ip ospf database

    Expected Output

    s1-leaf4#show ip ospf database

            OSPF Router with ID(10.111.254.4) (Instance ID 100) (VRF default)


                 Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum Link count
10.111.0.2      10.111.0.2      356         0x80000011   0x4670   6
10.111.0.1      10.111.0.1      355         0x80000011   0x3be    6
10.111.254.3    10.111.254.3    358         0x80000013   0x691    6
10.111.254.2    10.111.254.2    1198        0x8000000f   0x58f3   5
10.111.254.4    10.111.254.4    354         0x80000018   0x3b28   8
10.111.254.1    10.111.254.1    1198        0x8000000f   0x5ff8   5

                 Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#         Checksum
10.255.255.2    10.111.254.2    3600        0x80000116   0x6448
10.111.2.3      10.111.254.2    1198        0x80000002   0x5ded
10.111.2.1      10.111.254.1    1198        0x80000002   0x6de1
10.111.2.5      10.111.254.3    1198        0x80000002   0x4df9
10.111.1.1      10.111.254.1    1198        0x80000002   0x6ae6
10.111.1.5      10.111.254.3    1198        0x80000002   0x4afe
10.111.1.3      10.111.254.2    1198        0x80000002   0x5af2
s1-leaf4#show ip ospf database detail 10.111.254.1

            OSPF Router with ID(10.111.254.4) (Instance ID 100) (VRF default)

  LS Age: 1294
  Options: (E DC)
  LS Type: Router Links
  Link State ID: 10.111.254.1
  Advertising Router: 10.111.254.1
  LS Seq Number: 0x8000000f
  Checksum: 0x5ff8
  Length: 84
  Number of Links: 5

    Link connected to: a Transit Network
     (Link ID) Designated Router address: 10.111.1.1
     (Link Data) Router Interface address: 10.111.1.1
      Number of TOS metrics: 0
       TOS 0 Metrics: 10


    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.111.254.1
     (Link Data) Network Mask: 255.255.255.255
      Number of TOS metrics: 0
       TOS 0 Metrics: 10


    Link connected to: a Transit Network
     (Link ID) Designated Router address: 10.111.2.1
     (Link Data) Router Interface address: 10.111.2.1
      Number of TOS metrics: 0
       TOS 0 Metrics: 10


    Link connected to: a Transit Network
     (Link ID) Designated Router address: 10.255.255.2
     (Link Data) Router Interface address: 10.255.255.1
      Number of TOS metrics: 0
       TOS 0 Metrics: 10


    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.111.112.0
     (Link Data) Network Mask: 255.255.255.0
      Number of TOS metrics: 0
       TOS 0 Metrics: 10

    Command

    show ip route 10.111.112.0/24

    Expected Output

    s1-leaf4#show ip route 10.111.112.0/24

VRF: default
Source 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 - Other BGP Routes,
       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, M - Martian,
       DH - DHCP client installed default route,
       DP - Dynamic Policy Route, L - VRF Leaked,
       G  - gRIBI, RC - Route Cache Route,
       CL - CBF Leaked Route

 O        10.111.112.0/24 [110/30]
           via 10.111.1.6, Ethernet2
           via 10.111.2.6, Ethernet3
    Note

    ECMP is automatically enabled in OSPF as it is an IGP.

  2. Validate connectivity from s1-host1 to s1-host2. From s1-host1 execute:

    Commands

    ping 10.111.134.202

    traceroute 10.111.134.202

    a. Verify s1-leaf4's IP address is in the traceroute path, either interface 10.111.1.7 via s1-spine1 or interface 10.111.2.7 via s1-spine2. If traffic is hashing via s1-leaf3's 10.111.1.5 or 10.111.2.5 interfaces perform the optional shutdown steps below on s1-leaf3

    Commands

    interface Ethernet2-3
   shutdown

    b. Rerun traceroute/verification from s1-host1 to s1-host2 then revert the shutdown changes on s1-leaf3

    Commands

    interface Ethernet2-3
   no shutdown

Additional OSPF Features

  1. Route Redistribution: For fun, do a watch 1 diff show ip route | begin Gateway on s1-leaf1 and let that run while you execute the following commands on s1-leaf4. You will see the new route being injected into the route table of s1-leaf1.

    Commands

    ip route 0.0.0.0/0 Null0
!
router ospf 100
   redistribute static

  2. BFD: BFD is a low-overhead, protocol-independent mechanism which adjacent systems can use instead for faster detection of faults in the path between them. BFD is a simple mechanism which detects the liveliness of a connection between adjacent systems, allowing it to quickly detect failure of any element in the connection. Note that BFD is not running on the other devices so the BFD neighbor will not come up until you configure it on multiple devices.

    Commands

    router ospf 100
   bfd default
Success

Lab Complete!

Tip

The following additional commands are useful for troubleshooting OSPF:

  • show ip ospf summary
  • show ip ospf
  • show ip ospf neighbor
  • show run section ospf
  • show log