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ACI L3Out with both BGP and OSPF?

m1xed0s
Contributor
Contributor

Reference the screenshot below captured on a v4.2 fabric. Does it mean if I have both OSPF and BGP configured under the same L3Out, BGP would take precedence over OSPF for advertising fabric BD prefixes externally? If so, it is something new I learned I guess...

What about one L3Out using OSPF and another L3Out using BGP under the same VRF? Does this restriction/limitation still apply? 

Screenshot 2022-08-10 170522.png

1 Accepted Solution

Accepted Solutions

Hi @m1xed0s ,


multiple routing protocols under a single L3Out is not possible? 

Correct. Multiple routing protocols under a single L3Out is not possible.


I would do a EIGRP L3Out, an OSPF L3Out and a BGP L3Out if I needed to advertise a BD subnet into multiple protocols concurrently?

Correct again. From the ACI Fabric L3Out Guide


Cisco ACI allows only one routing protocol per L3Out with one exception. BGP and OSPF can be configured in the same L3Out as an exception in order to be able to use OSPF as the IGP for BGP.

 

RedNectar aka Chris Welsh. Forum Tips: 1. Paste images inline then edit>Image Size Large- don't attach. 2. Always mark helpful and correct answers, it helps others find what they need.

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3 Replies 3

RedNectar
Advocate
Advocate

Hi @m1xed0s ,

Ticking BOTH boxes (BGP and OSPF) does not enable both protocols to run as if you had completed two configurations.

Thankfully, the messages that appear in the L3Out wizard make this clearer now than it was in previous versions.  What you are actually configuring is BGP, but by checking the OSPF box you are saying that OSPF is your IGP when using BGP multi-hop and rather than using a static route to peer it uses OSPF learning. It does not talk OSFP.

[Many thanks for my colleague TC for helping with this answer]

 

 

RedNectar aka Chris Welsh. Forum Tips: 1. Paste images inline then edit>Image Size Large- don't attach. 2. Always mark helpful and correct answers, it helps others find what they need.

So if I read your reply correctly, multiple routing protocols under a single L3Out is not possible? If so, I would do a EIGRP L3Out, an OSPF L3Out and a BGP L3Out if I needed to advertise a BD subnet into multiple protocols concurrently?

Hi @m1xed0s ,


multiple routing protocols under a single L3Out is not possible? 

Correct. Multiple routing protocols under a single L3Out is not possible.


I would do a EIGRP L3Out, an OSPF L3Out and a BGP L3Out if I needed to advertise a BD subnet into multiple protocols concurrently?

Correct again. From the ACI Fabric L3Out Guide


Cisco ACI allows only one routing protocol per L3Out with one exception. BGP and OSPF can be configured in the same L3Out as an exception in order to be able to use OSPF as the IGP for BGP.

 

RedNectar aka Chris Welsh. Forum Tips: 1. Paste images inline then edit>Image Size Large- don't attach. 2. Always mark helpful and correct answers, it helps others find what they need.
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