Topology:
Use configuration from L3PVN task #1 as initial configuration for this task.
Requirements:
1. Change the configuration so SP network structure won't be visible to customer users when running traceroute command from one site to another.
2. Add link between routers R4 and R8. Include this link in OSPF area 0.
3. Configure the network so traffic between routers R4 and R8 use SP cloud when available, and direct R4-R8 link as backup only.
Solution:
Highlight the text below to reveal the solution.
This task requires understanding of the following technologies and features:
MPLS TTL propagation
OSPF Sham links
Requirement #1 - disable MPLS TTL propagation on SP routers to "hide" the SP network topology.
Requirement #2 & 3 - Sham link is required in order to prefer L3VPN link over the backdoor link between sites. Note that you also need to increase the cost of the backdoor link to make it the less preferred path.
!
no mpls ip propagate-ttl
!
no mpls ip propagate-ttl
vrf forwarding CUST_B
ip address 17.0.2.4 255.255.255.255
This task requires understanding of the following technologies and features:
MPLS TTL propagation
OSPF Sham links
Requirement #1 - disable MPLS TTL propagation on SP routers to "hide" the SP network topology.
Requirement #2 & 3 - Sham link is required in order to prefer L3VPN link over the backdoor link between sites. Note that you also need to increase the cost of the backdoor link to make it the less preferred path.
R1 & R5:
!
no mpls ip propagate-ttl
!
R2:
!
no mpls ip propagate-ttl
!
interface Loopback1vrf forwarding CUST_B
ip address 17.0.2.4 255.255.255.255
!
router ospf 1 vrf CUST_B
router-id 2.2.2.2
domain-id type 0005 value 000000000001
area 0 sham-link 17.0.2.4 17.0.3.8
redistribute bgp 17 subnets
!
R3:
interface Loopback1
vrf CUST_B
ipv4 address 17.0.3.8 255.255.255.255
!
router ospf CUST_B
vrf CUST_B
router-id 3.3.3.3
domain-id type 0005 value 000000000001
redistribute bgp 17
area 0
sham-link 17.0.3.8 17.0.2.4
cost 1
!
interface GigabitEthernet0/0/0/1
!
!
!
!
mpls ip-ttl-propagate disable
!
R4:
!
interface GigabitEthernet0/0/0/1
bandwidth 1000
ipv4 address 10.10.48.4 255.255.255.0
!
router ospf 1
router-id 10.10.4.4
area 0
interface Loopback0
!
interface GigabitEthernet0/0/0/0
!
interface GigabitEthernet0/0/0/1
!
!
!
R8:
!
interface Ethernet0/1
bandwidth 1000
ip address 10.10.48.8 255.255.255.0
ip ospf 1 area 0
!
Verification:
TTL propagation disable:
Before:
R8#traceroute 10.10.4.4 source lo0
Type escape sequence to abort.
Tracing the route to 10.10.4.4
VRF info: (vrf in name/id, vrf out name/id)
1 17.0.38.3 1 msec 1 msec 1 msec
2 17.0.13.1 [MPLS: Labels 16/25 Exp 0] 3 msec 3 msec 3 msec
3 17.0.24.2 [MPLS: Label 25 Exp 0] 2 msec 1 msec 1 msec
4 17.0.24.4 3 msec * 2 msec
After:
R8#traceroute 10.10.4.4 source lo0 numeric
Type escape sequence to abort.
Tracing the route to 10.10.4.4
VRF info: (vrf in name/id, vrf out name/id)
1 17.0.38.3 7 msec 1 msec 1 msec
2 17.0.13.1 [MPLS: Labels 16/25 Exp 0] 3 msec 3 msec 2 msec
3 17.0.24.4 2 msec * 2 msec
Backdoor link R4-R8:
R8#sh 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
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
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O 10.10.4.4/32 [110/22] via 17.0.38.3, 11:25:37, Ethernet0/0
C 10.10.8.8/32 is directly connected, Loopback0
C 10.10.48.0/24 is directly connected, Ethernet0/1
L 10.10.48.8/32 is directly connected, Ethernet0/1
17.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O E2 17.0.2.4/32 [110/1] via 17.0.38.3, 11:36:30, Ethernet0/0
O E2 17.0.3.8/32 [110/1] via 17.0.38.3, 11:32:26, Ethernet0/0
O 17.0.24.0/24 [110/21] via 17.0.38.3, 11:25:37, Ethernet0/0
C 17.0.38.0/24 is directly connected, Ethernet0/0
L 17.0.38.8/32 is directly connected, Ethernet0/0
RP/0/0/CPU0:R4#show route
Tue Jan 5 20:08:27.798 UTC
Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
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, E - EGP
i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
U - per-user static route, o - ODR, L - local, G - DAGR
A - access/subscriber, a - Application route, (!) - FRR Backup path
Gateway of last resort is not set
L 10.10.4.4/32 is directly connected, 17:42:48, Loopback0
O 10.10.8.8/32 [110/13] via 17.0.24.2, 11:26:24, GigabitEthernet0/0/0/0
C 10.10.48.0/24 is directly connected, 11:41:55, GigabitEthernet0/0/0/1
L 10.10.48.4/32 is directly connected, 11:41:55, GigabitEthernet0/0/0/1
O E2 17.0.2.4/32 [110/1] via 17.0.24.2, 11:32:57, GigabitEthernet0/0/0/0
O E2 17.0.3.8/32 [110/1] via 17.0.24.2, 11:34:18, GigabitEthernet0/0/0/0
C 17.0.24.0/24 is directly connected, 17:42:48, GigabitEthernet0/0/0/0
L 17.0.24.4/32 is directly connected, 17:42:48, GigabitEthernet0/0/0/0
O 17.0.38.0/24 [110/12] via 17.0.24.2, 11:27:31, GigabitEthernet0/0/0/0
R2#show ip ospf sham-links
Sham Link OSPF_SL0 to address 17.0.3.8 is up
Area 0 source address 17.0.2.4
Run as demand circuit
DoNotAge LSA allowed. Cost of using 1 State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40,
Hello due in 00:00:04
Adjacency State FULL (Hello suppressed)
Index 2/2, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
R2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/ - - 17.0.3.8 OSPF_SL0
10.10.4.4 1 FULL/DR 00:00:36 17.0.24.4 Ethernet1/0
RP/0/0/CPU0:R3#show ospf vrf CUST_B neighbor
Tue Jan 5 20:10:22.499 UTC
* Indicates MADJ interface
Neighbors for OSPF CUST_B, VRF CUST_B
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/ - - 17.0.2.4 OSPF_SL0
Neighbor is up for 11:34:53
10.10.8.8 1 FULL/BDR 00:00:32 17.0.38.8 GigabitEthernet0/0/0/1
Neighbor is up for 17:23:05
RP/0/0/CPU0:R3#show ospf vrf CUST_B sham-links
Tue Jan 5 20:10:32.229 UTC
Sham Links for OSPF CUST_B, VRF CUST_B
Sham Link OSPF_SL0 to address 17.0.2.4 is up
Area 0, source address 17.0.3.8
IfIndex = 2
Run as demand circuit
DoNotAge LSA allowed., Cost of using 1
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:08
Adjacency State FULL (Hello suppressed)
Number of DBD retrans during last exchange 0
Index 2/2, retransmission queue length 0, number of retransmission 0
First 0(0)/0(0) Next 0(0)/0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
