Delegate subscriber IP allocation to external DHCP server

[VikrantDigiCat]

Hi,

Is there anyway to enable use of Enterprise DHCP sitting on the N6 Gateway to handle the UE IP Address allocation? We have this feature in our Enterprise 5G Core that we use from another vendor. It helps us to identify the specific UE sending a particular traffic/packet at the N6 gateway and then route it accordingly within our network.

[gruyaume]

Hello @VikrantDigiCat ,

Thanks for reaching out.

This is an interesting feature. Ella Core does not support delegating UE IP address allocation to an external DHCP server. IP allocation is handled entirely internally. Supporting external DHCP would likely require implementing a DHCP relay client and managing lease lifecycles — it's something we could consider for a future release.

That said, if your goal is purely about routing UE traffic, you can use BGP Today to advertise UE subnet routes to your enterprise network. Guide here. You can also view UE traffic flows via the Usage page.

[VikrantDigiCat]

Hi @gruyaume,
Thanks for confirming this.

In that case, could you please guide me to any page that details the use/function of NAT: Enable/Disable option in EllaCore?
In our Enterprise Core: Enabling NAT enables the use of an internal IP Pool for UE and Disabling NAT forwards the DHCP request to the Enterprise DHCP server on our N6 Gateway.

[ghislainbourgeois]

Hi @VikrantDigiCat,

To enable NAT, you can go to the Networking page, and you will find a NAT tab with a toggle switch to enable or disable NAT. When enabled, the UEs will use the internal IP Pool, but will be translated to the IP address used on the N6 interface.

In Ella Core, we currently only support IP sessions. In your deployment, do the UE themselves send a DHCP request? That would require an Ethernet session, and it is possible according to the specs, but we do not support those sessions at the moment.

Otherwise, the Enterprise Core might be sending DHCP requests on behalf of the UEs, and in that case I would be curious what is being used as a MAC address to identify the different UEs.

This is an interesting feature that we could consider adding, but we would need to understand the use case a bit better.

[VikrantDigiCat]

Hi @ghislainbourgeois,
The Core sends the DHCP requests on behalf of the UEs and the Core gives you an option to either use the same mac as that of the UE or generate a dummy mac applicable for that very session.
This kind of a feature is very useful in highly secure 5G Testbeds where you want the traffic of X UE connected to A-5G Network be routed securely to Y UE connected to B-5G Network.
This is also useful in Testbeds where you want only a specific UE to have access to a Mobile Edge Compute entity sitting somewhere in the network behind the N6.

[ghislainbourgeois]

Thank you, this clarifies things very well. We will discuss this internally and evaluate the effort.

[VikrantDigiCat]

@ghislainbourgeois Thank you so much for your prompt response. If you want, you can move this discussion to the "ideas" section.

[gruyaume]

I am reopening the discussion since the idea has not been implemented nor discarded.

However, I need to better understand the relation between the usecase/rationale and the proposal. The goal to "ensure highly secure 5G environment where traffic of X UE connected to A-5G Network is routed securely to Y UE connected to B-5G Network" can be addressed without external DHCP:

• BGP integration: Route subscriber traffic in your enterprise environment (already supported)
• Flow-based policies: Fined-grained ACL-like policies allowing/denying subscriber traffic (coming soon)

That said, I understand external DHCP may still be needed if your enterprise network is tightly integrated with your DHCP infrastructure. Is that the case here, or would the features above cover your requirements?

[gruyaume]

Flow-based policies are available in Ella Core v1.9, network administrators can configure allow/deny fine grained rules.

[cjwolff]

Hi folks,

I'm in the early stages of planning a large scale deployment so this is a great idea. In an enterprise I can imagine having a central gateway with DHCP probes (Like Cisco ISE) tracking UE origin and hops between cores.

In a disaster scenario I may deploy dual cores in a zone for redundancy if one is lost and backhaul up to my cloud gateway through a pair of starlink or similar.

Thank you all for everything you do.

Christopher

[gruyaume]

We're working on adding High Availability (HA) support in Ella Core. The design isn't final yet but individual Cores would get their IP (or IP pools) from the cluster leader. We will likely need to enhance the BGP integration so that each node dynamically advertises and withdraws the prefixes it owns.

We may add support for external DHCP integration, but it's not a pre-requisite for HA.