Layer 3 mode
Details about using Layer 3 (L3) with OVHcloud Connect
Details about using Layer 3 (L3) with OVHcloud Connect
Last updated 14th September 2020
Learn more about Layer 3 implementation and connection for the OVHcloud Connect solution.
OVHcloud Connect configured in Layer 3 differs from Layer 2 as you have to configure the L3 domain on each PoP/EntryPoint and DC/EndPoint.
A Layer 3 domain is composed of:
The L3 domain is an IP routing instance provided by OVHcloud. Traffic is forwarded between PoP/EntryPoint and DC/Endpoint, not between two PoPs/EntryPoints. There is no need for internal IP addressing between PoP/EntryPoint and DC/EndPoint. In the data centre, the routing instance inside the L3 domain is composed of two devices, labelled ‘A’ and ‘B’.
Based on this principle it is possible to manage several OVHcloud Connect services.
As a result, L3 makes it compatible with a multi-DC configuration.
The two examples above illustrate the configuration of two OVHcloud Connect services, as one OVHcloud Connect equals one PoP/EntryPoint.
Rules:
The following schema shows the mix of L2 and L3. They can end in the same OVHcloud data centre or not.
On such an architecture, two L3 domains are needed: PoP/EntryPoint and DC/EndPoint.
"IP Net A" is part of the L3 Domain in the DC. The following rules apply:
IP address | Role |
---|---|
A.B.C.0 | Subnet |
A.B.C.1 | OVHcloud virtual router address (if enabled) |
A.B.C.2 | OVHcloud router A |
A.B.C.3 | OVHcloud router B |
"IP Net B" is part of the L3 Domain in the PoP. The following rules apply:
IP address | Role |
---|---|
A.B.C.0 | Subnet |
A.B.C.1 | OVHcloud router |
A.B.C.2 | Customer router |
A.B.C.3 | Subnet broadcast |
VRRP allows router redundancy on OVHcloud devices.
BGP is mandatory in a PoP/EntryPoint and optional in a DC/EndPoint. Enabling BGP in a DC/EndPoint disables VRRP configuration.
For example, IP network 'B' will be announced to the OVHcloud router through BGP session.
At a more global level, BGP topology will look like this:
By default, all available paths are enabled using ECMP, with up to 4 paths supported. To have an active/passive topology with two PoPs/EntryPoints, you can use AS path prepending or MED.
If AS path prepending is configured on the customer's devices in PoP2, the topology will look like this:
Note: AS path prepending is not configurable on OVHcloud devices.
Using MED is an alternative to achieve the same topology.
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