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Beginner

Cisco ACI - Bridge Domain/EPG lost communication

Hi all,

On Cisco ACI environment we have configured under tenant "common", vrf "Yellow", one Bridge Domain (BD_gateway_Yellow) with 3 lan:

Gw 1: 10.123.1.1/25

Gw 2: 10.123.1.129/25

Gw 3: 10.123.2.1/24

 

Each lan are used in a specific EPG:

Gw 1 --> EPG: Network

Gw 2 --> EPG: Storage

Gw 3 --> EPG: Unix

 

Each EPG have a contract that permit to contact those lans from networks that are outside Cisco ACI environment (L3out).

We have a problem just with the LAN 1: every client that are in this EPG, lost randomly connection to gateway and between clients. After some attempts to solve this problem, the solution was to create a new BD (BD_gateway_Network) just for lan 1, used only from EPG Network. With this configuration, there are not issue in connectivity.

 

My question is why the problem seems to be only for the lower subnet 10.123.1.0/25 and not for the higher 10.123.1.129/25?

Cisco ACI permits to create a L3 on BD and use it in specific EPG, and if we want we can do segmentation under a specific EPG, but in this case seems that the problem in only on lower subnet /25.

 

Kind regards,

Marco

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5 REPLIES 5
Beginner

Re: Cisco ACI - Bridge Domain/EPG lost communication

When you create Subnet on BD , it is actually  gateway IP.   So 10.123.1.0/25 and  10.123.2.0/24 are not valid config. 

Also, EPG is assoiated with the BD , not some "Lan" 

Highlighted
Rising star

Re: Cisco ACI - Bridge Domain/EPG lost communication

Hi @marco1305 ,

@6askorobogatov is absolutely correct.

What you will need to so is:

  1. Find out what the default gateway IP address of the hosts on Lan 1: 10.123.1.0/25 is. I will assume it is 10.123.1.1/25
  2. Remove the Lan 1: 10.123.1.0/25 IP from your BD_gateway_Yellow Bridge Domain
  3. Add 10.123.1.1/25 (or whatever the default gateway IP is) to your BD_gateway_Yellow Dridge Domain
    1. Note: If this address already exists somewhere else (e.g. on a router) remove it first
  4. Find out what the default gateway IP address of the hosts on Lan 3: 10.123.2.0/24 is. I will assume it is 10.123.2.1/24
  5. Remove the Lan 3: 10.123.2.0/24 IP from your BD_gateway_Yellow Bridge Domain
  6. Add 10.123.2.1/25 (or whatever the default gateway IP is) to your BD_gateway_Yellow Dridge Domain
    1. Note: If this address already exists somewhere else (e.g. on a router) remove it first

I hope this helps

 



Don't forget to mark answers as correct if it solves your problem. This helps others find the correct answer if they search for the same problem


RedNectar
aka Chris Welsh


Don't forget to mark answers as correct if it solves your problem. This helps others find the correct answer if they search for the same problem

Beginner

Re: Cisco ACI - Bridge Domain/EPG lost communication

Hi @RedNectar , @6askorobogatov 

 

Thank you very much for your support.

I've correct the information on my post: actually, the configurations on BD are with default gateway .1 and not with .0.

My problem is that hosts in 10.123.1.1/25 lose randomly communication. On higher subnet 10.123.1.129/25 we don't have problems. The same on 10.123.2.0/24 where all works fine.

 

Is it possible that on Cisco ACI is better to configure a /24 instead of two /25, and do what we usually did with subnetting, using EGP segmentation?

 

Thank you,

Marco

Beginner

Re: Cisco ACI - Bridge Domain/EPG lost communication

No, ACI happily supports any length netmask , including /31

Re: Cisco ACI - Bridge Domain/EPG lost communication

I dont know weather this is correct or not Please check the l3BD on flood
or Proxy mode. it should on Proxy mode as i know.
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