BGP best-path selection algorithm on Meraki MX one-armed concentrator

CSV
Comes here often

BGP best-path selection algorithm on Meraki MX one-armed concentrator

Hi,

 

Does anyone have Meraki documentation related to BGP best-path selection algorithm?

 

From my testing environment I've noticed that a MX in one-armed concentrator mode (the only mode that supports eBGP) always prefers the eBGP route over iBGP route (it doesn't care of AS-PATH length)

 

Ex:

 

R1(AS 100)----eBGP----HUB1-----iBGP(AS 65100)-----HUB2----R2 (AS 200)

 

R1 advertises subnet 10.10.10.10/32 with AS path 100 100 100

R2 advertises subnet 10.10.10.10/32 with AS path 200

 

 

--> Hub1 prefers the external route from R1 (would expect to prefer the route from Hub2)

--> Hub2 prefers the external route from R2 (expected behavior)

 

--> If R1 stops advertising 10.10.10.10/32, then Hub1 will receive the route from Hub2 via iBGP with AS PATH 65100 200

 

--> If Spoke 1 has in the hub list HUB1(primary) HUB2(secondary), it will prefer the route from HUB2 with AS PATH 65100 200

 

thanks

 

 

 

 

4 REPLIES 4
CptnCrnch
Kind of a big deal
CSV
Comes here often

Hi CptnCrnch,

 

My post is not related to your link.

 

thanks

 
PhilipDAth
Kind of a big deal

I haven't seen any documentation covering the BGP path selection process.

MarcoSch
Here to help

Hi,

 

Do have a look at the following CiscoLive 2018 presentation: BRKCRS-2103 Integrating the Meraki SD WAN Solution with the traditional Enterprise network. The presentation covers several subjects including BGP based path selection for a one-armed concentrator.

 

The presentation and recording should be available via ciscolive.com

 

Regards,

Marco.

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