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Multiple /32 IP host subnets configured under Miicro-EPGs ?

richard.thomas
Level 1
Level 1

Hi there

Just trying to understand what reasons there could be (if any!) for configuring multiple /32 host subnets under a Micro EPG when no inter tenant or inter vrf route leaking is required. The micro EPG itself also defines the IP host addresses as uSeg attributes. I've tried searching support documentation but unfortunately nothing came up specific to my question. Any help would be greatly appreciated, thanks. 

7 Replies 7

M02@rt37
VIP
VIP

Hello @richard.thomas,

Configuring multiple /32 host subnets under a Micro EPG can serve various purposes, even if inter-tenant or inter-VRF route leaking is not required. Without further information about your specific use case, it is difficult to provide an accurate answer.

But, few potential considerations:

Each /32 host subnet represents a unique host or endpoint within the Micro EPG. By assigning a separate subnet to each host, you can achieve granular isolation and segmentation. This can be useful in scenarios where strict separation is needed between individual endpoints within the same EPG == isolation and segmentation.

Using /32 host subnets allows for efficient IP address management and allocation. It provides a dedicated IP address for each host, making it easier to track and manage IP assignments within the Micro EPG. This can be beneficial in large-scale deployments or environments where IP address utilization needs to be closely monitored == IP address MGMT. 

Assigning each host a separate /32 subnet enables precise policy enforcement at the individual host level. With distinct subnets, you can apply specific policies, such as access control rules or QOS settings, tailored to each host's requirements. This level of granularity can enhance security and performance management within the Micro EPG ==policy enforcement

Even if current requirements don't demand inter-tenant or inter-VRF route leaking, the decision to use /32 subnets may be driven by future scalability considerations. By provisioning each host with its own subnet, you can easily expand or modify the network architecture in the future without needing to readdress or reconfigure existing subnets == future scalability

 

Best regards
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richard.thomas
Level 1
Level 1

Thanks for the prompt response. Just taking one of your considerations for a moment:-

"Assigning each host a separate /32 subnet enables precise policy enforcement at the individual host level. With distinct subnets, you can apply specific policies, such as access control rules or QOS settings, tailored to each host's requirements. This level of granularity can enhance security and performance management within the Micro EPG ==policy enforcement"

How would you go about applying a specific policy, such as access control rules to each host in the micro-EPG, as contract filters as far as I'm aware (please correct me if I'm wrong) don't allow you to define IP addresses (subnets or /32 host addresses) ?

So for example I might have 10 x /32 host subnets all defined under the one micro-EPG....so how do you apply "precise policy enforcement at the individual host level"?

 

@richard.thomas,

You're correct that contract filters in a micro-EPG typically do not allow you to define IP addresses directly. However, there are other ways to achieve precise policy enforcement at the individual host level within a micro-EPG. Here are a few approaches:

--CBAC allows you to define access control policies based on attributes such as source/destination IP addresses, ports, protocols, and other criteria. While you may not be able to define IP addresses directly in contract filters, you can leverage CBAC to create access control policies that match specific host IP addresses or subnets within the micro-EPG.

-- Instead of defining policies directly on the micro-EPG, you can create multiple Endpoint Groups within the micro-EPG, each representing a specific host. Then, you can define contracts between these EPGs to enforce policy at the individual host level. The contracts can contain filters that match the IP addresses or subnets of the individual hosts.

By adopting these approaches, you can achieve a higher level of granularity and apply specific policies to individual hosts within the micro-EPG.

Best regards
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richard.thomas
Level 1
Level 1

Hi, again thanks for you response.

Apologies but I'm still unsure how either of the above approaches is achieved through the APIC (we are currently running version 4.2(7)). Can you please expand on how this is achieved IE. APIC menu options etc....  

I can see how creating a uEPG for each host might work by setting the uSeg Attributes to match against the specific IP /32 host address, but this would not explain the defining of the subnet as the /32 host address when inter Tenant/vrf is not required.

Sorry for my persistence but I just don't get how it's possible to achieve precise policy enforcement at the individual host level within a micro-EPG.

Many thanks in advance.

Sergiu.Daniluk
VIP Alumni
VIP Alumni

Hi Richard,

Using uSeg EPG subnet configuration for segmentation is only possible if you use the "Yes" option for "IP" attribute:

SergiuDaniluk_0-1687782092821.png

Otherwise, subnet will not play too much role in segmentation.

 

Take care,

Sergiu

 

Robert Burns
Cisco Employee
Cisco Employee

Another use case for defining a /32 host subnet under any EPG (base or Micro) is to disable IP Learning for that endpoint - in case of an L4-7 device that has a floating VIP.  

RobertBurns_0-1687782142881.png

 

Robert

richard.thomas
Level 1
Level 1

Many thanks all, really appreciate your responses.

 

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