Configure VRF Leaks on IOS XE

Introduction

This document describes and provides example configurations for common methods of Virtual Routing and Forwarding (VRF) route leaking.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

• Border Gateway Protocol (BGP)
• Routing Protocol Redistribution
• VRF
• Cisco IOS® XE Software

For more information on these topics, see:

Redistribute Routing Protocols

Mutual Redistribution Between EIGRP and BGP Configuration Example

Understand Redistribution of OSPF Routes into BGP

Components Used

The information in this document is based on Routers with Cisco IOS® XE versions 16.12.X and 17.X

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Background Information

VRF allows a router to maintain separate routing tables for different virtual networks. When exceptions are needed, VRF route leaking allows some traffic to be routed between the VRFs without the use of static routes.

Scenario 1 - VRF Route Leak between BGP and IGP ( EIGRP )

Scenario 1 provides an example of VRF route leaking between BGP and EIGRP. This method can be used for other IGPs.

Network Diagram

The Network Diagram as seen in Image 1 shows the layer 3 topology where route leaking is needed.


Image 1. Route Leaking Topology for Scenario 1

Router LEAK has a BGP neighborship to a neighbor in VRF A, and an EIGRP neighbor in the global VRF.  Device 192.168.11.11 needs to be able to connect to device 172.16.10.10 across the network.

Router LEAK cannot route between the two since the routes are in different VRFs.  These routing tables show the current routes per VRF, and indicate which routes need to be leaked between the global VRF and VRF A.

LEAK routing tables:

LEAK#show ip route 
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, GigabitEthernet2
L 192.168.1.1/32 is directly connected, GigabitEthernet2
192.168.11.0/32 is subnetted, 1 subnets
D 192.168.11.11 [90/130816] via 192.168.1.2, 02:30:29, GigabitEthernet2 >> Route to be exchange to the VRF A routing table. 

LEAK#show ip route vrf A

Routing Table: A
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, GigabitEthernet1
L 10.0.0.1/32 is directly connected, GigabitEthernet1
172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.2, 01:47:58 >> Route to be exchange to the global routing table.

Configure

Complete the procedures to create the leak between the two routing tables:

Step 1.
Create route-maps to filter the routes to be injected in both routing tables.

LEAK(config)#Route-map VRF_TO_EIGRP
LEAK(config-route-map)#match ip address prefix-list VRF_TO_EIGRP
LEAK(config-route-map)#exit
!
Prefix-list created to match the host that is attached to the previous route-map configured.
!
ip prefix-list VRF_TO_EIGRP permit 172.16.10.10/32

or

LEAK(config)#Route-map VRF_TO_EIGRP
LEAK(config-route-map)# match ip address 10 
LEAK(config-route-map)#exit
!
ACL created to match the host that is attached to the previous route-map.
!
LEAK#show ip access-lists 10 
10 permit 172.16.10.10

LEAK(config)#Route-map EIGRP_TO_VRF
LEAK(config-route-map)#match ip address prefix-list EIGRP_TO_VRF 
LEAK(config-route-map)#exit
LEAK(config)#
!
Prefix-list created to match the host that is attached to the previous route-map configured.
!
ip  prefix-list EIGRP_TO_VRF  permit 192.168.11.11/32

or

LEAK(config)#Route-map EIGRP_TO_VRF
LEAK(config-route-map)#match ip address 20 
LEAK(config-route-map)#exit
LEAK(config)#
!
ACL created to match the host that is attached to the previous route-map.
!
LEAK#show ip access-list 20
10 permit 192.168.11.11


Step 2.
Define the import/export maps and add the route-map names.

LEAK(config)#vrf definition A 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#import ipv4 unicast map EIGRP_TO_VRF >> Import the global routing table routes at the VRF routing table.
LEAK(config-vrf-af)#export ipv4 unicast map VRF_TO_EIGRP >> Export the VRF routes to the Global Routing Table.
LEAK(config-vrf-af)#end

Step 3. 
Proceed with the dual redistribution.

Redistribute EIGRP 

LEAK(config)#router bgp 1
LEAK(config-router)#redistribute eigrp 1 
LEAK(config-router)#end

Redistribution BGP

LEAK(config)#router eigrp 1
LEAK(config-router)#redistribute bgp 1 metric 100 1 255 1 1500 
LEAK(config-router)#end

Verify

Routing table from VRF A 

LEAK#show ip route vrf A

Routing Table: A

< Snip for resume >

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, GigabitEthernet1
L 10.0.0.1/32 is directly connected, GigabitEthernet1
172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.2, 00:58:53
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
B 192.168.1.0/24 is directly connected, 00:01:00, GigabitEthernet2
L 192.168.1.1/32 is directly connected, GigabitEthernet2
192.168.11.0/32 is subnetted, 1 subnets 
B 192.168.11.11 [20/130816] via 192.168.1.2, 00:01:00, GigabitEthernet2 >> Route from global routing table at VRF A routing table.

Global Routing Table (EIGRP)

LEAK#show ip route 

< snip for resume >

Gateway of last resort is not set

172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.2 (A), 00:04:47  >> Route from VRF A at global routing table.
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, GigabitEthernet2
L 192.168.1.1/32 is directly connected, GigabitEthernet2
192.168.11.0/32 is subnetted, 1 subnets
D 192.168.11.11 [90/130816] via 192.168.1.2, 01:03:35, GigabitEthernet2
LEAK#

Scenario 2 - VRF Leaking between VRF A and VRF B

Scenario 2 describes the leak between two different VRFs.

Network Diagram

This documents uses this network setup:

Image 2. Route Leaking Topology for Scenario 2

Router LEAK has a BGP neighborship to a neighbor in VRF A, and an OSPF neighbor in the VRF B. Device 192.168.11.11 needs to connect to device 172.16.10.10 across the network.

Router LEAK cannot route between the two since the routes are in different VRFs. These routing tables show the current routes per VRF, and indicate which routes need to be leaked between the VRF A and VRF B.

LEAK Routing Table:

LEAK#show ip route vrf A

Routing Table: A
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, Ethernet0/0
L 10.0.0.2/32 is directly connected, Ethernet0/0
172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.1, 00:03:08 >> Route to be exchange to routing table VRF B.  

LEAK#show ip route vrf B

Routing Table: B
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, Ethernet0/1
L 192.168.1.2/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
O 192.168.11.11 [110/11] via 192.168.1.1, 00:58:45, Ethernet0/1 >> Route to be exchange to routing table VRF A.

Configure

Complete these procedures to create the leak between the two routing tables:

Step 1.
Create route-maps to filter the routes to be injected in both routing tables.

LEAK(config)#Route-map VRFA_TO_VRFB 
LEAK(config-route-map)#match ip address prefix-list VRFA_TO_VRFB 
LEAK(config-route-map)#exit
!
Prefix-list created to match the host and IP segment that is attached to the previous route-map configured.
!
ip prefix-list VRFA_TO_VRFB permit 172.16.10.10/32
ip prefix-list VRFA_TO_VRFB permit 10.0.0.0/30

or

LEAK(config)#Route-map VRFA_TO_VRFB 
LEAK(config-route-map)#match ip address 10 
LEAK(config-route-map)#exit
!
ACL created to match the host and IP segment that is attached to the previous route-map.
!
LEAK#show ip access-lists 10
10 permit 172.16.10.10
20 permit 10.0.0.0


LEAK(config)#Route-map VRFB_TO_VRFA 
LEAK(config-route-map)#match ip address prefix-list VRFB_TO_VRFA 
LEAK(config-route-map)#exit
!
Prefix-list created to match the host and IP segment that is attached to the previous route-map configured.
!
ip prefix-list VRFB_TO_VRFA permit 192.168.11.11/32
ip prefix-list VRFB_TO_VRFA permit 192.168.1.0/24

or

LEAK(config)#Route-map VRFB_TO_VRFA 
LEAK(config-route-map)#match ip address 20 
LEAK(config-route-map)#exit
!
ACL created to match the host and IP segment that is attached to the previous route-map configured.
!
LEAK#show ip access-lists 20 
10 permit 192.168.11.11
20 permit 192.168.1.0

Step 2.
At the VRFs configure the import/export map, use the route-map names to leak the routes.

LEAK(config)#vrf definition A 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#export map VRFA_TO_VRFB 
LEAK(config-vrf-af)#import map VRFB_TO_VRFA 


LEAK(config)#vrf definition B 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#export map VRFB_TO_VRFA 
LEAK(config-vrf-af)#import map VRFA_TO_VRFB 

Step 3.
Add the route-target to import and export the route distinguisher from both VRFs.

! --- Current configuration for VRF A

vrf definition A
rd 1:2
!
address-family ipv4
route-target export 1:2 
route-target import 1:1 
exit-address-family

! --- Current configuration from VRF B

vrf definition B
rd 2:2
!
address-family ipv4
exit-address-family

! --- Import the routes from VRF  B into VRF A

LEAK(config)#vrf definition A 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#route-target import 2:2  

! --- Import routes from VRF A to VRF B and export routes from VRF B

LEAK(config-vrf-af)#vrf definition B 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#route-target import 1:2 
LEAK(config-vrf-af)#route-target export 2:2 

Verify

Check the Routing Tables 

VRF A Routing Table 

LEAK#show ip route vrf A

Routing Table: A

< Snip for resume >

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, Ethernet0/0
L 10.0.0.2/32 is directly connected, Ethernet0/0
172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.1, 00:07:20
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
B 192.168.1.0/24 is directly connected, 00:00:10, Ethernet0/1
L 192.168.1.2/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
B 192.168.11.11 [20/11] via 192.168.1.1 (B), 00:00:10, Ethernet0/1 >> Route from VRF B routing table at VRF A. 

VRF B Routing Table 

LEAK#show ip route vrf B
Routing Table: B

< Snip for resume >

10.0.0.0/30 is subnetted, 1 subnets
B 10.0.0.0 [200/0] via 10.0.0.1 (A), 00:00:15
172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [200/0] via 10.0.0.1 (A), 00:00:15 >> Route from VRF A routing table at VRF B. 
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, Ethernet0/1
L 192.168.1.2/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
O 192.168.11.11 [110/11] via 192.168.1.1, 01:05:12, Ethernet0/1 

Scenario 3 - VRF Leaking between OSPF (VRF) and EIGRP (Global) with BGP (Optional)

Scenario 3 describes the route leak between two IGPs (VRF B and Global VRF).

Network Diagram

This document uses this network setup:

Image 3. Route Leaking Topology for Scenario 3

Router LEAK has an OSPF neighborship to a neighbor in VRF B, and an EIGRP neighbor in the global VRF. Device 172.16.10.10 needs to be able to connect to device 192.168.11.11 across the network.

Router LEAK is not able to connect these two hosts. These routing tables show the current routes per VRF, and indicate which routes need to be leaked between the VRF B and Global VRF.

LEAK Routing Table:

LEAK#show ip route 
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, Ethernet0/1
L 192.168.1.1/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
D 192.168.11.11 [90/1024640] via 192.168.1.2, 01:08:38, Ethernet0/1 >> Route to be exchange from global routing table at VRF B routing table.

LEAK#show ip route vrf B

Routing Table: B
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, Ethernet0/0
L 10.0.0.2/32 is directly connected, Ethernet0/0
172.16.0.0/32 is subnetted, 1 subnets
O 172.16.10.10 [110/11] via 10.0.0.1, 01:43:45, Ethernet0/0 >> Route to be exchange from routing table VRF B at global routing table.

Configure

Complete this procedures to create the leak between the two routing tables:

Step 1.
Create route-maps for import and export to be injected in both routing tables.

LEAK(config)#Route-map OSPF_TO_EIGRP
LEAK(config-route-map)#match ip address prefix-list OSPF_TO_EIGRP 
LEAK(config-route-map)#exit
!
Prefix-list created to match the host that is attached to the previous route-map configured.
!
ip prefix-list OSPF_TO_EIGRP permit 172.16.10.10/32
ip prefix-list OSPF_TO_EIGRP permit 10.0.0.0/30

or

LEAK(config)#Route-map OSPF_TO_EIGRP 
LEAK(config-route-map)#match ip address 10 
LEAK(config-route-map)#exit
!
ACL created to match the host that is attached to the previous route-map.
!
LEAK#show ip access-lists 10 
10 permit 172.16.10.10
20 permit 10.0.0.0

LEAK(config)#Route-map EIGRP_TO_OSPF 
LEAK(config-route-map)#match ip address prefix-list EIGRP_TO_OSPF 
LEAK(config-route-map)#exit
!
Prefix-list created to match the host that is attached to the previous route-map configured.
!
ip prefix-list EIGRP_TO_OSPF permit 192.168.11.11/32
ip prefix-list EIGRP_TO_OSPF permit 192.168.1.0/24

or

LEAK(config)#Route-map EIGRP_TO_OSPF 
LEAK(config-route-map)#match ip address 20
LEAK(config-route-map)#exit
!
ACL created to match the host that is attached to the previous route-map.
!
LEAK#show ip access-lists 20
10 permit 192.168.11.11
20 permit 192.168.1.0/24

Step 2.
Add the import/export maps in order to match the route-map names.

Current configuration
!
vrf definition B
rd 1:2 
!
address-family ipv4 
exit-address-family
!
!
LEAK(config-vrf)#vrf definition B 
LEAK(config-vrf)#address-family ipv4 
LEAK(config-vrf-af)#import ipv4 unicast map EIGRP_TO_OSPF
LEAK(config-vrf-af)#export ipv4 unicast map OSPF_TO_EIGRP

Step 3.
To perform the leak is necessary to create a BGP process, in order to redistribute 
the IGPs protocols.

router bgp 1
bgp log-neighbor-changes
! 
address-family ipv4 vrf B >> Include the address-family to inject VRF B routing table (OSPF)
!
exit-address-family

Note: Ensure that the VRF has a Route Distinguisher configured in order to avoid the error:
"%vrf B does not have rd configured, configure "rd" before configuring import route-map"

Step 4.
Create a Dual Redistribution.

IGPs redistribution.

LEAK(config-router)#router bgp 1 
LEAK(config-router)#redistribute eigrp 1
!
LEAK(config-router)#address-family ipv4 vrf B 
LEAK(config-router-af)#redistribute ospf 1 match internal external 1 external 2 
LEAK(config-router-af)#end

BGP Redistribution

LEAK(config)#router ospf 1 vrf B 
LEAK(config-router)#redistribute bgp 1
!
LEAK(config-router)#router eigrp TAC
LEAK(config-router)# 
LEAK(config-router)# address-family ipv4 unicast autonomous-system 1
LEAK(config-router-af)# 
LEAK(config-router-af)# topology base
LEAK(config-router-af-topology)#redistribute bgp 1 metric 100 1 255 1 1500

Verify

Check the Routing Tables

LEAK#show ip route

< Snip for resume >

172.16.0.0/32 is subnetted, 1 subnets
B 172.16.10.10 [20/11] via 10.0.0.1, 00:14:48, Ethernet0/0 >> Route from VRF B routing table at global routing table ( EIGRP ). 
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, Ethernet0/1
L 192.168.1.1/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
D 192.168.11.11 [90/1024640] via 192.168.1.2, 02:16:51, Ethernet0/1

LEAK#show ip route vrf B
Routing Table: B

< Snip for resume >

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/30 is directly connected, Ethernet0/0
L 10.0.0.2/32 is directly connected, Ethernet0/0
172.16.0.0/32 is subnetted, 1 subnets
O 172.16.10.10 [110/11] via 10.0.0.1, 00:34:25, Ethernet0/0
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
B 192.168.1.0/24 is directly connected, 00:08:51, Ethernet0/1
L 192.168.1.1/32 is directly connected, Ethernet0/1
192.168.11.0/32 is subnetted, 1 subnets
B 192.168.11.11 [20/1024640] via 192.168.1.2, 00:08:51, Ethernet0/1 >> Route from global routing table ( EIGRP ) at VRF B routing table.

Scenario 4 - VRF Default Route Leak from OSPF to BGP

Scenario 4 provides an example of VRF default route leaking from OSPF to BGP.

Network Diagram

The Network Diagram as seen in Image 4 shows the layer 3 topology where default route leaking is needed.

Image 4. Route Leaking Topology for Scenario 4

OSPF and BGP process are running in different VRF on Router LEAK. The default route is present in Router OSPF. Router LEAK has a BGP neighborship in VRF A with Router BGP, and an OSPF neighbourship in VRF B with Router OSPF. 

Default route leak from OSPF to BGP on Router LEAK is demonstrated below.

Configure

Step 1
Check if a static default route is present in Router OSPF.

OSPF#sh ip route

<output snipped>

Gateway of last resort is 192.168.10.2 to network 0.0.0.0 

S* 0.0.0.0/0 [1/0] via 192.168.10.2   >>> default route is present in the routing table.
C 192.168.0.0/24 is directly connected, GigabitEthernet2
L 192.168.0.2/32 is directly connected, GigabitEthernet2
192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.10.0/24 is directly connected, GigabitEthernet1
L 192.168.10.1/32 is directly connected, GigabitEthernet1


Step 2
From the OSPF router, the default route needs to be advertised in OSPF to Router LEAK.

Use the command "default-information originate" on Router OSPF under OSPF process:( if there is static route in the OSPF router, routing table as verified in Step 1)


OSPF(config)#router ospf 1
OSPF(config-router)#default-information originate


If there is no static route in the Router OSPF routing table then we can generate and advertise a default route to the OSPF neighbour.


OSPF(config)#router ospf 1
OSPF(config-router)#default-information originate always

This forces the router to advertise a default route even if it doesn't have one in its routing table.


Step 3.1
Verify on Router LEAK, if an external OE2 route is installed in the VRF B routing table:

LEAK#sh ip route VRF B

Routing Table: B

<output snipped>

Gateway of last resort is 192.168.0.2 to network 0.0.0.0

O*E2 0.0.0.0/0 [110/1] via 192.168.0.2, 00:05:51, GigabitEthernet2 >>> OE2 route is installed in the VRF B routing table (This needs to be leaked in BGP)
192.168.0.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.0.0/24 is directly connected, GigabitEthernet2
L 192.168.0.1/32 is directly connected, GigabitEthernet2

Step 3.2
Configure a prefix-list on Router LEAK

LEAK# conf t
LEAK(config)# ip prefix-list OSPF_TO_BGP seq 5 permit 0.0.0.0/0

Configure a route-map to match the prefix-list.

LEAK(config-route-map)#route-map OSPF_TO_BGP permit 10
LEAK(config-route-map)# match ip address prefix-list OSPF_TO_BGP
LEAK(config-route-map)#exit

Step 3.3
Verify on Router LEAK, that required VRFs , Route Distinguishers (RD) an Route Targets (RT) are configured.

LEAK(config)#vrf definition A
LEAK(config-vrf)#rd 1:1
LEAK(config-vrf)#address-family ipv4
LEAK(config-vrf-af)#route-target import 6500:1
LEAK(config-vrf-af)#exit-address-family
LEAK(config-vrf-af)#end
LEAK#

LEAK(config)#vrf definition B
LEAK(config-vrf)#rd 2:2
LEAK(config-vrf)#address-family ipv4
LEAK(config-vrf-af)#route-target export 6500:1
LEAK(config-vrf-af)#exit-address-family
LEAK(config-vrf-af)#end
LEAK#

Step 3.4
Configure import map in VRF A.

LEAK#conf t
LEAK(config)#vrf definition A
LEAK(config-vrf)#address-family ipv4
LEAK(config-vrf-af)#import map OSPF_TO_BGP
LEAK(config-vrf-af)#end
LEAK#


Step 3.5 
Create an address family VRF B in the BGP configuration and advertise “0.0.0.0”

LEAK#sh run | sec bgp
redistribute bgp 6501
router bgp 6501
bgp router-id 10.0.0.1
bgp log-neighbor-changes
!
address-family ipv4 vrf A
neighbor 10.0.0.2 remote-as 6500
neighbor 10.0.0.2 activate
exit-address-family
!
address-family ipv4 vrf B
network 0.0.0.0
exit-address-family

Note: Creating an address family VRF with in the BGP works even without activating any neighbour. Just spawning the BGP process is necessary to leak the routes between the VRF.

Verify

Verify the default route available in BGP.

LEAK#sh ip route vrf A

Routing Table: A

<output snipped>

Gateway of last resort is 192.168.0.2 to network 0.0.0.0

B* 0.0.0.0/0 [20/1] via 192.168.0.2 (B), 00:15:36, GigabitEthernet2 >>> Default route of VRF B routing table in VRF A routing table.
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.0.0.0/24 is directly connected, GigabitEthernet1
L 10.0.0.1/32 is directly connected, GigabitEthernet1

Additional Resources