Tuesday, January 26, 2016

L3VPN task #2. CE-PE routing using OSPF - part 2.

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. 

R1 & R5: 


!
no mpls ip propagate-ttl
!


R2: 



!
no mpls ip propagate-ttl
!
interface Loopback1
 vrf 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

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