Cisco ACI Routing advertise same network from different BorderLeaf and server's connected on BoderLeaf

[mcusine]

Hi support forum,

I attach a picture of my topology where you can see one ACI Fabric on different physical CPD's but connected by dark fiber (500 meters between them).

We have border leaf on two sites where connect some legacy equipment’s and servers.

Two routers legacy that we connect to border work as Active-Standby, the problem is when we connect a Server on the same border (i know that is not the site but we need to do) because on the border where the active legacy router is connected the routing table see the same network 10.0.0.0/24 learned local by OSPF (preferred) and from the fabric by MBGP. This is right.

But on the border where is connected the standby legacy router the server the routing table for 10.0.0.0/24 is learned from ospf standby legacy router and from MBGP from the fabric, in this case the server connected to this border will use the local ospf route.

Any idea for how to force the border where the standby legacy router is connected to use the route of the border where is connected the active legacy router, in other words we want to have symmetric traffic.

We have some ideas:

1) Connect border's and legacy routers on the same L3 out sharing the same network segment.

2) Modify the BGP admin distance (don't know if possible on ACI) to a lower value that ospf.

Thanks and King regards,

[Manuel Velasco]

Hi Mcusine,

Have you looked into configuring the interleak routing policy?  

This policy allows you to modify attributes for interleak or leaking of routes to BGP such as community, preference, and metric from OSPF

Cisco ACI and Interleak of External Routes

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/kb/b_KB_Configuring_Interleak_of_External_Routes.html