Dynamic inter-VRF communication explained
Page 18 | Configure VRF-lite
Dynamic inter-VRF communication explained
The following section explains how VRF routing domain isolation is maintained, and how
routes that exist in one VRF instance are leaked to another VRF instance via BGP.
Only BGP
can be used to dynamically leak routes from one VRF instance to another.
The Forwarding Information Base (FIB) and routing protocols
Associated with each VRF instance is an IP route table, also known as the Forwarding
Information Base (FIB). When BGP address-families (associated with VRF instances) are
configured, a corresponding BGP route table is created for each VRF instance on which a
BGP address-family is configured.
VRF Device
VRF
blue
FIB
BGP
address-
family
blue
RIP
address-
family
blue
OSPF 2
VRF
red
FIB
BGP
address-
family
red
RIP
address-
family
red
OSPF 1
BGP routes copied between BGP
address-families to facilitate inter-VRF
communication
Similarly, when RIP address-families (associated with VRF instances) are configured, a
corresponding RIP route table is created for each VRF instance on which a RIP address-family
is configured.
Similarly, when OSPF instances (associated with VRF instances) are configured, a
corresponding OSPF route table is created for each VRF instance on which an OSPF instance
is configured.
Each dynamic routing protocol automatically selects appropriate routes and copies them to
the FIB.
Static and connected routes are automatically added to the FIB when they are created.
