Arista L3 Leaf/Spine Step by Step (1) - Basic Config (BGP/MLAG)

(updated Dec 20, 2018 for more platforms)

Topology:


 

Following my previous post.  In this post, I cover the basic IP, BGP, and MLAG configuration. Here we use eBGP as routing protocol instead of OSPF or ISIS because it is the most common design in the modern data center. You can check the following 2 links for more details. 

• RFC 7938 - BGP Routing in Data Centers, by Petr Lapukhov
• BGP in an Arista Data Center

Basic eBGP configurations:

All BGP peers import ONLY a /32 network NLRI of loopback10, which is VXLAN source address. So no network p2p ethernet NRLI nor "redistribute connect". As a result, the routing table size is very minimal and only ping from local loopback to remote routers' works. 

router bgp 65041
   router-id 200.255.255.12
   maximum-paths 16 ecmp 16
   ....
   network 200.255.200.12/32   !!! loopback10's host addr.
!
interface Loopback10
   ip address 200.255.200.12/32

!!! direct ping doesn't work

ckp342.vtepX2#ping 200.255.200.56
PING 200.255.200.56 (200.255.200.56) 72(100) bytes of data.

--- 200.255.200.56 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 40ms

!!! ping source from loopback 10 works

ckp342.vtepX2#ping 200.255.200.56 source 200.255.200.12
PING 200.255.200.56 (200.255.200.56) from 200.255.200.12 : 72(100) bytes of data.
80 bytes from 200.255.200.56: icmp_seq=1 ttl=63 time=0.230 ms
80 bytes from 200.255.200.56: icmp_seq=2 ttl=63 time=0.140 ms
80 bytes from 200.255.200.56: icmp_seq=3 ttl=63 time=0.128 ms
80 bytes from 200.255.200.56: icmp_seq=4 ttl=63 time=0.109 ms
80 bytes from 200.255.200.56: icmp_seq=5 ttl=63 time=0.127 ms

--- 200.255.200.56 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.109/0.146/0.230/0.045 ms, ipg/ewma 0.208/0.186 ms

If multiple leaves share the AS# (not in this setup),  you need "neighbor spine.v4 allowas-in 3" to accept BGP NLRI between each other. 

router bgp 65010

   router-id 10.255.255.11

   neighbor spine.v4 allowas-in 3

eBGP and MLAG configuration

• The mlag configuration here is quite normal. 
• Only one thing worthy to note that, the 2 mlag peers use the same vxlan source address, shown as below

VtepA1: 

interface Loopback10

   ip address 200.255.200.34/32

!

router bgp 65021

   router-id 200.255.255.3

   network 200.255.200.34/32

!

interface Vxlan1

   vxlan source-interface Loopback10

LeafA2:

interface Loopback10

   ip address 200.255.200.34/32

!

router bgp 65021

   router-id 200.255.255.4

   network 200.255.200.34/32

!

interface Vxlan1

   vxlan source-interface Loopback10

Zip file of all routers' "show run"