VRF Support in DHCPv4
One device can have multiple containers of routing tables or Forwarding Information Bases
(FIBs), with one routing table for each VRF instance. A VRF-capable router can function
as a group of multiple virtual routers on the same physical router.
Inter-VRF route leaking allows leaking of
specific route prefixes from one VRF instance to another on the same physical router,
which eliminates the need for external routing.
In a DHCP setting, route leaking is controlled
through one DHCP server (which may be on a different VRF) so that multiple VRFs can
communicate with that server.
DHCP relay is supported in the following
configurations.
- Same VRF instance as the interface through which the client is connected
- For example:
- VE interface 100 in VRF "red"
- IP address of interface - 3.1.1.1/24
- IP DHCP Relay address (20.1.1.2)
- Different VRF instance as the interface through which the client is connected,
an inter-VRF deployment
- For example:
- VE interface 100 in default VRF
- IP address of interface -
3.1.1.1/24
- IP DHCP Relay address
(100.1.1.2) in VRF "blue"
- IP DHCP Relay address
(1.2.3.4.6) in VRF "red"
- A maximum of 128 inter-VRF IP DHCP Relay address configurations is allowed per
node. A VRF route leak configuration is required for these configurations. In
this example, a VRF route leak configuration is required on the default VRF as
follows:
- ip route 100.1.1.2/32
next-hop-vrf blue <exit interface/next-hop-ip>
- ip route 12.3.4.6/32
next-hop-vrf red <exit interface/next-hop-ip>
- For inter-VRF deployment, use the use-vrf
vrf-name option with the ip dhcp relay
address command, where vrf-name is the VRF
where the DHCP server is located.
Note
As a best practice, do not configure the same DHCP relay address on different VRFs.
For example:
- VE interface 100 in default VRF
- IP address of interface - 3.1.1.1/24
- IP DHCP Relay address (30.1.1.2) in VRF
"blue"
- IP DHCP Relay address (30.1.1.2) in VRF
"red"
