Posted on June 13, 2021 2:54 am
 |  Asked by tedd kelley
 |  97 views
RESOLVED
0
0
Print Friendly, PDF & Email

As someone who understands the Cisco implementation of VXLAN relatively well, I would like to hear a better/fuller explanation of the BGP attribute D-Path and how it is implemented in Arista VXLAN.

0
Answered on June 14, 2021 9:27 am

Hi Tedd Kelley,

Thanks for reaching out.

Domain Path Attribute (D-PATH):

The BGP D-PATH attribute is an optional and transitive BGP path attribute.

The use of this attribute is to avoid routes being re-advertised back into the originating domain i.e this is used for loop prevention when internetworking between EVPN and IPVPN domains.

Routes are not re-advertised into the Domain, which have their Domain-ID in the D-path

You can refer to the below TOI link for more information regarding D-path and usecase:

https://eos.arista.com/eos-4-23-2f/evpn-internetworking-with-ipvpn/#Loop_Avoidance_using_D-PATH

Sample configuration:

We don't have a knob that will prevent IPVPN and EVPN routes from being mutually imported/exported between address-families.To prevent a loop it is recommend configuring a domain identifier under EVPN and IPVPN by making sure "bgp bestpath d-path" is configured as well:

switch(conf)#router bgp 64512
bgp bestpath d-path  >>Include D-path in the BGP route selection

!

address-family evpn
neighbor VXLAN_EVPN activate
domain identifier 65001:2         >>EVPN peering session,  D-path Attribute for the EVPN domain
!
address-family vpn-ipv4
neighbor iBGP_RR activate
neighbor default encapsulation mpls next-hop-self source-interface Loopback0
domain identifier 64512:2        >>IP-VPN peering session, D-path Attribute for the IP-VPN domain

You can also refer to the below link for more detailed explanation of D-path attribute and its composition:

https://datatracker.ietf.org/doc/draft-ietf-bess-evpn-ipvpn-interworking/

 

 

Thanks,

Bhavana.

Post your Answer

You must be logged in to post an answer.