Passthrough Configuration

Underlay Configuration #

For passthrough mode, the underlay configuration is simpler than EVPN mode as it doesn’t require VTEP IP allocation. The configuration focuses on establishing BGP sessions with external routers.

Basic Underlay Configuration #

apiVersion: openpe.openperouter.github.io/v1alpha1
kind: Underlay
metadata:
  name: underlay
  namespace: openperouter-system
spec:
  asn: 64514
  nics:
    - toswitch
  neighbors:
    - asn: 64512
      address: 192.168.11.2

Configuration Fields #

Field	Type	Description	Required
`asn`	integer	Local ASN for BGP sessions	Yes
`nics`	array	List of network interface names to move to router namespace	Yes
`neighbors`	array	List of BGP neighbors to peer with	Yes

Note: Unlike EVPN mode, passthrough mode does not require an evpn field in the underlay configuration since no VTEP IP allocation is needed.

L3 Passthrough Configuration #

L3 Passthrough configurations define direct BGP connectivity between the host and the fabric without encapsulation. Each L3Passthrough creates a BGP session with BGP-speaking components on the host.

Basic L3Passthrough Configuration #

apiVersion: openpe.openperouter.github.io/v1alpha1
kind: L3Passthrough
metadata:
  name: passthrough
  namespace: openperouter-system
spec:
  hostsession:
    asn: 64514
    hostasn: 64515
    localcidr:
      ipv4: 192.169.10.0/24

Configuration Fields #

Field	Type	Description	Required
`hostsession.asn`	integer	Router ASN for BGP session with host	Yes
`hostsession.hostasn`	integer	Host ASN for BGP session	Yes
`hostsession.localcidr.ipv4`	string	IPv4 CIDR for veth pair IP allocation	No
`hostsession.localcidr.ipv6`	string	IPv6 CIDR for veth pair IP allocation	No

Dual Stack Configuration #

You can configure both IPv4 and IPv6 for dual stack support:

apiVersion: openpe.openperouter.github.io/v1alpha1
kind: L3Passthrough
metadata:
  name: passthrough-dual
  namespace: openperouter-system
spec:
  hostsession:
    asn: 64514
    hostasn: 64515
    localcidr:
      ipv4: 192.169.10.0/24
      ipv6: 2001:db8:10::/64

IP Allocation Strategy #

The IP addresses for the veth pair are allocated from the configured localcidr:

Router side: Always gets the first IP in the CIDR (e.g., 192.169.10.1)
Host side: Each node gets a different IP from the CIDR, starting from the second value (e.g., 192.169.10.2)

This consistent allocation strategy ensures that BGP-speaking components on the host can always use the same router IP address for establishing BGP sessions.

What Happens During Reconciliation #

When you create or update L3Passthrough configurations, OpenPERouter automatically:

Creates Veth Pair: Sets up a veth pair named pt-host (host side) and pt-ns (router side)
Assigns IP Addresses: Allocates IPs from the localcidr range:
- Router side: First IP in the CIDR (e.g., 192.169.10.1)
- Host side: Second IP in the CIDR (e.g., 192.169.10.2)
Establishes BGP Session: Opens BGP session between router and host using the specified ASNs
Configures Route Advertisement: Sets up route advertisement for both IPv4 and IPv6 address families

API Reference #

For detailed information about all available configuration fields, validation rules, and API specifications, see the API Reference documentation.