Virtual routing and forwarding(VRF) implementation in Linux about uemacs HOT 1 OPEN

@JADAUN-SINGH Hi, you can refer to the kernel documentation below.
Setup:

1. VRF device is created with an association to a FIB table.
   e.g, ip link add vrf-blue type vrf table 10
   ip link set dev vrf-blue up

2. An l3mdev FIB rule directs lookups to the table associated with the device.
   A single l3mdev rule is sufficient for all VRFs. The VRF device adds the
   l3mdev rule for IPv4 and IPv6 when the first device is created with a
   default preference of 1000. Users may delete the rule if desired and add
   with a different priority or install per-VRF rules.

   Prior to the v4.8 kernel iif and oif rules are needed for each VRF device:
   ip ru add oif vrf-blue table 10
   ip ru add iif vrf-blue table 10

3. Set the default route for the table (and hence default route for the VRF).
   ip route add table 10 unreachable default metric 4278198272

   This high metric value ensures that the default unreachable route can
   be overridden by a routing protocol suite. FRRouting interprets
   kernel metrics as a combined admin distance (upper byte) and priority
   (lower 3 bytes). Thus the above metric translates to [255/8192].

4. Enslave L3 interfaces to a VRF device.
   ip link set dev eth1 master vrf-blue

   Local and connected routes for enslaved devices are automatically moved to
   the table associated with VRF device. Any additional routes depending on
   the enslaved device are dropped and will need to be reinserted to the VRF
   FIB table following the enslavement.

   The IPv6 sysctl option keep_addr_on_down can be enabled to keep IPv6 global
   addresses as VRF enslavement changes.
   sysctl -w net.ipv6.conf.all.keep_addr_on_down=1

5. Additional VRF routes are added to associated table.
   ip route add table 10 ...

More info check: VRF_Linux

from uemacs.