10-21-2019 06:28 PM - edited 10-21-2019 06:31 PM
Hi everyone,
Looking for some advice.
We're looking at building 2 connections and tunnels with an end client, one of the connections will reside in DCA and the other in DCB.
The end client will be advertising the same prefix, lets say 192.168.24.0/24. All traffic will be initiated outbound to the client site. We're looking at doing an Active/Standby setup where all traffic will traverse DCA (no load sharing), unless DCAs connection goes down, then DCB will take over and route traffic out of the secondary link.
My thoughts are to first ensure the prefixes are accepted/flooded via BGP in DCA and DCB. Ensure IBGP is setup in between DCA and DCB to ensure both sites are sharing the routes. My final idea was to set up a route-map and prefix list in DCA on the bgp peering router with a higher local preference, for eg, 200. If the routes are flooded throughout both cores, the routes should traverse DCA (preferred path), until that route is no longer active, and then DCBs route will be installed in the routing table.
Is this setup and solution correct, or does anyone have advice on how they would design it? As another solution thought of, can the client advertise the prefix to us via DCA with higher priority so no route manipulation is required on my side? A third solution though of would be to accept difference prefixes from both sites, but I'm trying to figure out a solution with the one prefix advertised to both sites to save address space and complexity with the network/security controls.
Thank you!
10-21-2019 09:11 PM
10-22-2019 04:19 AM - edited 10-22-2019 04:19 AM
Hi Francesco,
The client will be advertising the prefix to us. We will be sending outbound traffic from our site to the clients pointing towards the advertised subnet. Would the simplest solution to simply have the client AS Path Prepend the prefix advertised out of DCB?
Thanks
10-22-2019 05:05 AM
Hello
@kramer977 wrote:
Hi Francesco,
The client will be advertising the prefix to us. We will be sending outbound traffic from our site to the clients pointing towards the advertised subnet. Would the simplest solution to simply have the client AS Path Prepend the prefix advertised out of DCB?
Thanks
Not really - AS-path preference is further down the route-path selection process, local preferance would be better option on received routes
10-22-2019 06:48 AM - edited 10-22-2019 08:29 AM
I figured it would help to create a quick diagram to show the bigger picture (attached)
Most end users who are initiating traffic is primarily flowing through DCA.
With both prefixes advertising, I will be accepting them via BGP from both DCs via AS2, AS3, AS4.
Maybe this clears things up a bit better, would love to hear what options are available from both the client and our end? If we have the client AS Path Prepend on the secondary circuit, do I also need to add preference for the outbound traffic?
10-22-2019 07:38 AM
Hello
as stated previously I would suggest you utilise Local Preference PA for path selection within you DCs for the received routes from you clients additionally you could also incorporate bfg community values this way dc rtrs wiil assign LP on the routes assigned to a particular bgp community - meaning you could have many clients with routes coupled in say two community values and have the dcs path select on these two values as to which path they take for each community
10-23-2019 07:05 PM
10-23-2019 11:15 PM - edited 10-23-2019 11:17 PM
Hello @Francesco Molino
Looking at it again you could possibly be right -
"The end client will be advertising the same prefix, lets say 192.168.24.0/24.
All traffic will be initiated outbound to the client site
The diagram shows a heading of "Client" with DCA/DCB underneath it - then a Heading of "OUR SITE" with end users.
So I am now confused!
10-22-2019 07:05 AM
For inbound direction you can use AS path prepend. It's the easiest option. For outbound direction, use LP.
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