Layer 3 Leaf-Spine with BGP¶

Note

The manually entered commands that are part of this lab are equivalent to L3LS_s1-leaf4_complete.

Preparing The Lab¶

Log into the LabAccess jumpserver:
1. Type l3ls at the Main Menu prompt.
  
  Info
  
  Did you know the l3ls 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_s1-spine1, L3LS_s1-spine2, L3LS_s1-leaf1, L3LS_s1-leaf2, L3LS_s1-leaf3, and L3LS_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¶

Configure the vARP MAC Address in Global Configuration mode.

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

Configure the VLAN, SVI, and 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 BGP¶

Configure BGP on the s1-leaf4 switch using the following criteria.

Based on the diagram, configure L3 interfaces to s1-spine1 and 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

Validate the configuration with the following command:

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

Based on the diagram, enable BGP and configure the neighbor relationships on s1-leaf4. They will be eBGP to s1-spine1 and s1-spine2, and iBGP to s1-leaf3.

Peer Groups

We are using a peer group to configure the neighbor attributes for the spines. This allows us to apply all bgp attributes within a group to each neighbor that is a member in a scalable method.

Commands

router bgp 65102
router-id 10.111.254.4
neighbor SPINE peer group
neighbor SPINE remote-as 65100
neighbor SPINE send-community standard extended
neighbor 10.111.1.6 peer group SPINE
neighbor 10.111.2.6 peer group SPINE
neighbor 10.255.255.1 remote-as 65102
neighbor 10.255.255.1 next-hop-self

iBGP Peering Info

Since neighbor 10.255.255.1 has a remote-as of 65102, this specifies an iBGP peering relationship (because the ASN is the same as this switch 65102). As such, the receiving switch may not have a route to networks more than 1 hop away, hence the switches should each advertise that they are the next hop via the neighbor 10.255.255.1 next-hop-self statement. While this scenario is only 2 iBGP peers, in a network fabric with several iBGP peers, a switch inside an AS (and not on an edge) may not have a route to a switch in any external AS.

Validate the configuration and BGP neighbor peerings.

Command

show active

Expected Output

s1-leaf4(config-router-bgp)#show active
router bgp 65102
    router-id 10.111.254.4
    neighbor SPINE peer group
    neighbor SPINE remote-as 65100
    neighbor SPINE send-community standard extended
    neighbor 10.111.1.6 peer group SPINE
    neighbor 10.111.2.6 peer group SPINE
    neighbor 10.255.255.1 remote-as 65102
    neighbor 10.255.255.1 next-hop-self

Command

show ip bgp summary

Expected Output

s1-leaf4(config-router-bgp)#show ip bgp summary
BGP summary information for VRF default
Router identifier 10.111.254.4, local AS number 65102
Neighbor Status Codes: m - Under maintenance
Neighbor     V AS           MsgRcvd   MsgSent  InQ OutQ  Up/Down State   PfxRcd PfxAcc
10.111.1.6   4 65100             10         8    0    0 00:01:02 Estab   5      5
10.111.2.6   4 65100              9         9    0    0 00:01:02 Estab   5      5
10.255.255.1 4 65102              9         8    0    0 00:01:00 Estab   9      9

Configure networks on s1-leaf4 to advertise to s1-spine1 and s1-spine2.

Commands

router bgp 65102
    network 10.111.134.0/24
    network 10.111.254.4/32

Verify these networks are being advertised to other spines and leafs.

From s1-leaf issue the following commands:

Command

show ip route

Expected Output

s1-leaf1#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 - 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

    Gateway of last resort is not set

    B E      10.111.0.1/32 [200/0] via 10.111.1.0, Ethernet2
    B E      10.111.0.2/32 [200/0] via 10.111.2.0, Ethernet3
    C        10.111.1.0/31 is directly connected, Ethernet2
    B E      10.111.1.0/24 [200/0] via 10.111.1.0, Ethernet2
    C        10.111.2.0/31 is directly connected, Ethernet3
    B E      10.111.2.0/24 [200/0] via 10.111.2.0, Ethernet3
    C        10.111.112.0/24 is directly connected, Vlan112
    B E      10.111.134.0/24 [200/0] via 10.111.1.0, Ethernet2
    C        10.111.254.1/32 is directly connected, Loopback0
    B I      10.111.254.2/32 [200/0] via 10.255.255.2, Vlan4094
    B E      10.111.254.3/32 [200/0] via 10.111.1.0, Ethernet2
    B E      10.111.254.4/32 [200/0] via 10.111.1.0, Ethernet2
    C        10.255.255.0/30 is directly connected, Vlan4094
    C        192.168.0.0/24 is directly connected, Management0

Command

show ip bgp

Expected Output

s1-leaf1#show ip bgp
BGP routing table information for VRF default
Router identifier 10.111.254.1, local AS number 65101
Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP
                    S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
                    % - Pending BGP convergence
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI Origin Validation codes: V - valid, I - invalid, U - unknown
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

            Network                Next Hop              Metric  AIGP       LocPref Weight  Path
* >      10.111.0.1/32          10.111.1.0            0       -          100     0       65100 i
*        10.111.0.1/32          10.255.255.2          0       -          100     0       65100 i
* >      10.111.0.2/32          10.111.2.0            0       -          100     0       65100 i
*        10.111.0.2/32          10.255.255.2          0       -          100     0       65100 i
* >      10.111.1.0/24          10.111.1.0            0       -          100     0       65100 ?
*        10.111.1.0/24          10.255.255.2          0       -          100     0       65100 ?
* >      10.111.2.0/24          10.111.2.0            0       -          100     0       65100 ?
*        10.111.2.0/24          10.255.255.2          0       -          100     0       65100 ?
* >      10.111.112.0/24        -                     -       -          -       0       i
*        10.111.112.0/24        10.255.255.2          0       -          100     0       i
* >      10.111.134.0/24        10.111.1.0            0       -          100     0       65100 65102 i
*        10.111.134.0/24        10.111.2.0            0       -          100     0       65100 65102 i
*        10.111.134.0/24        10.255.255.2          0       -          100     0       65100 65102 i
* >      10.111.254.1/32        -                     -       -          -       0       i
* >      10.111.254.2/32        10.255.255.2          0       -          100     0       i
* >      10.111.254.3/32        10.111.1.0            0       -          100     0       65100 65102 i
*        10.111.254.3/32        10.111.2.0            0       -          100     0       65100 65102 i
*        10.111.254.3/32        10.255.255.2          0       -          100     0       65100 65102 i
* >      10.111.254.4/32        10.111.1.0            0       -          100     0       65100 65102 i
*        10.111.254.4/32        10.111.2.0            0       -          100     0       65100 65102 i
*        10.111.254.4/32        10.255.255.2          0       -          100     0       65100 65102 i

Enable multiple paths by configuring ECMP. On s1-leaf4, jump into BGP configuration mode and add:

Commands

router bgp 65102
    maximum-paths 2

Verify ECMP by checking the routing tables on s1-leaf4 as well as each of the Spines:

Commands s1-spine1

show ip route

Expected Output

s1-spine1#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 - 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

Gateway of last resort is not set

C        10.111.0.1/32 is directly connected, Loopback0
C        10.111.1.0/31 is directly connected, Ethernet2
C        10.111.1.2/31 is directly connected, Ethernet3
C        10.111.1.4/31 is directly connected, Ethernet4
C        10.111.1.6/31 is directly connected, Ethernet5
S        10.111.1.0/24 is directly connected, Null0
B E      10.111.112.0/24 [200/0] via 10.111.1.1, Ethernet2
                                 via 10.111.1.3, Ethernet3
B E      10.111.134.0/24 [200/0] via 10.111.1.5, Ethernet4
                                 via 10.111.1.7, Ethernet5
B E      10.111.254.1/32 [200/0] via 10.111.1.1, Ethernet2
                                 via 10.111.1.3, Ethernet3
B E      10.111.254.2/32 [200/0] via 10.111.1.1, Ethernet2
                                 via 10.111.1.3, Ethernet3
B E      10.111.254.3/32 [200/0] via 10.111.1.5, Ethernet4
                                 via 10.111.1.7, Ethernet5
B E      10.111.254.4/32 [200/0] via 10.111.1.5, Ethernet4
                                 via 10.111.1.7, Ethernet5
C        192.168.0.0/24 is directly connected, Management0

Commands s1-spine1

show ip bgp

Expected Output

BGP routing table information for VRF default
Router identifier 10.111.0.1, local AS number 65100
Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP
                    S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
                    % - Pending BGP convergence
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI Origin Validation codes: V - valid, I - invalid, U - unknown
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

            Network                Next Hop              Metric  AIGP       LocPref Weight  Path
* >      10.111.0.1/32          -                     -       -          -       0       i
* >      10.111.1.0/24          -                     -       -          -       0       ?
* >Ec    10.111.112.0/24        10.111.1.1            0       -          100     0       65101 i
*  ec    10.111.112.0/24        10.111.1.3            0       -          100     0       65101 i
* >Ec    10.111.134.0/24        10.111.1.5            0       -          100     0       65102 i
*  ec    10.111.134.0/24        10.111.1.7            0       -          100     0       65102 i
* >Ec    10.111.254.1/32        10.111.1.1            0       -          100     0       65101 i
*  ec    10.111.254.1/32        10.111.1.3            0       -          100     0       65101 i
* >Ec    10.111.254.2/32        10.111.1.3            0       -          100     0       65101 i
*  ec    10.111.254.2/32        10.111.1.1            0       -          100     0       65101 i
* >Ec    10.111.254.3/32        10.111.1.5            0       -          100     0       65102 i
*  ec    10.111.254.3/32        10.111.1.7            0       -          100     0       65102 i
* >Ec    10.111.254.4/32        10.111.1.7            0       -          100     0       65102 i
*  ec    10.111.254.4/32        10.111.1.5            0       -          100     0       65102 i

ECMP Success!

ECMP is now working - notice the new status code in the show ip bgp output on s1-spine1. Ec: E or e for ECMP, and c for Contributing to ECMP.

Test¶

We can now verify our configurations and validate connectivity on various devices in the topology.

Validate connectivity from s1-host1 to s1-host2.

From s1-host1 execute:

Commands
```
ping 10.111.134.202
```
Commands
```
traceroute 10.111.134.202
```
Verify s1-leaf4’s IP address is in the traceroute path, either interface IP 10.111.1.7 via s1-spine1 or interface IP 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
```
router bgp 65102
    neighbor 10.111.1.4 shutdown
    neighbor 10.111.2.4 shutdown
```
Re-run ping and traceroute verification from s1-host1 to s1-host2 then revert the shutdown changes on s1-leaf3:

Commands
```
router bgp 65102
    no neighbor 10.111.1.4 shutdown
    no neighbor 10.111.2.4 shutdown
```

Additional BGP Features¶

If you have some time, here are some additional features that can be configured in BGP.

Route Redistribution

For fun, issue a watch 1 diff show ip route | begin Gateway on s1-leaf1 and s1-leaf2, and let those run while you execute the command redistribute connected below on s1-leaf3. You will see new routes being injected into the route tables of s1-leaf1 and s1-leaf2.

Command
```
router bgp 65102
    redistribute connected
```

Route-Maps and Prefix-Lists

Below is an example of some basic Prefix-Lists and Route-Maps that can be used for BGP filtering. Note that this is just an example and will not impact route advertisement in the lab.

Configuration

ip prefix-list BOGON-Prefixes seq 10 permit 10.0.0.0/8
ip prefix-list BOGON-Prefixes seq 20 permit 172.16.0.0/12
ip prefix-list BOGON-Prefixes seq 30 permit 192.168.0.0/16
!
route-map BOGONS permit 10
    match ip address prefix-list BOGON-Prefixes
!
route-map BOGONS deny 20
!
route-map InboundSP1 deny 10
    sub-route-map BOGONS
!
route-map InboundSP1 permit 20
 set local-preference 200
!
router bgp 65102
    neighbor UpstreamSP1 route-map InboundSP1 in

BFD

BFD is a low-overhead, protocol-independent mechanism which adjacent systems can use 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.

Commands
```
router bgp 65102
    neighbor <neighbor_ip> bfd
```

Success

If your L3LS has been configured correctly and the routing table on s1-Leaf4 is complete, then s1-Host2 should be reachable from s1-Host1.

Tip

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

show ip bgp summary
show ip bgp
show ip bgp neighbor
show run section bgp
show log