Ticket #12

Ticket #12

Network diagram

IGP diagram

The problem:

R3, R1 and R5 can't ping R2's Lo0 IP address. Fix the problem without touching R1.


The solution:


First, lets check if R3 can ping R2's Lo0 IP address 8.7.0.2.

On R3:

R3#ping 8.7.0.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.7.0.2, timeout is 2 seconds:
..
Success rate is 0 percent (0/2)

Indeed R3 can't ping R2's Lo0 IP address. Lets check R3's routing table entry for R2's Lo0 IP address.

On R3:

R3#show ip route 8.7.0.2
Routing entry for 8.7.0.0/24
  Known via "connected", distance 0, metric 0 (connected, via interface)
  Routing Descriptor Blocks:
  * directly connected, via Loopback0
      Route metric is 0, traffic share count is 1

We can see that R3's Lo0 was accidentally configured as /24 route instead of /32. Lets fix that and check again R3's routing table entry for R2's Lo0.

On R3:

R3(config)#int lo 0
R3(config-if)#ip addr 8.7.0.3 255.255.255.255
R3(config-if)#do sh ip route 8.7.0.2
% Subnet not in table


Now the route to R2's Lo0 in not known, which means that now there is no 8.7.0.0/24 route, and that R3 got no routing information about R2's Lo0 IP address. Lets check if R3 got a default route.

On R3:

R3#sh ip route 0.0.0.0
% Network not in table

No default route on R3. Does R3 got any OSPF route?

On R3:

R3#sh ip route ospf
     8.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O IA    8.7.15.0/24 [110/2] via 8.7.35.5, 00:02:55, FastEthernet0/0
O       8.7.0.5/32 [110/2] via 8.7.35.5, 00:02:55, FastEthernet0/0

R3 got OSPF routes in its routing table, which means that R3 got an OSPF neighbor relationship with R5.


Lets move closer to R2 and check if R5 got a route to R2's Lo0 IP address, 8.7.0.2, or maybe got a default route.

On R5:

R5#sh ip route 8.7.0.2
% Subnet not in table
R5#sh ip route 0.0.0.0
% Network not in table

As we can see, R5's got no routing info for R2's Lo0 or a default route. Does R5 got any OSPF routes?

On R5:

R5#sh ip route ospf

     8.0.0.0/8 is variably subnetted, 4 subnets, 2 masks

O       8.7.0.3/32 [110/2] via 8.7.35.3, 00:24:44, FastEthernet0/1


R5 got only OSPF route to R3's Lo0 IP address. Does R5 got an OSPF neighbor relationship with R1?

On R5:

R5#sh ip ospf nei 

Neighbor ID     Pri   State           Dead Time   Address         Interface
8.7.0.3           1   FULL/BDR        00:00:31    8.7.35.3        FastEthernet0/1
8.7.0.1           1   FULL/DR         00:00:37    8.7.15.1        FastEthernet0/0

R5 got an OSPF neighbor relationship with R1, but it getting no routes from it. We should have seen R1's Lo0 IP address in R5's routing table.


Lets have a look at R1's routing table.

On R1:

R1#sh ip route
Codes: 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

Gateway of last resort is 8.7.15.5 to network 0.0.0.0

     8.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C       8.7.15.0/24 is directly connected, FastEthernet0/1
C       8.7.12.0/24 is directly connected, Serial1/0
O IA    8.7.0.5/32 [110/2] via 8.7.15.5, 00:33:07, FastEthernet0/1
O IA    8.7.0.3/32 [110/3] via 8.7.15.5, 00:31:39, FastEthernet0/1
C       8.7.0.1/32 is directly connected, Loopback0
O IA    8.7.35.0/24 [110/2] via 8.7.15.5, 00:32:57, FastEthernet0/1
O*IA 0.0.0.0/0 [110/2] via 8.7.15.5, 00:33:07, FastEthernet0/1

We can see that R5 is the one injecting the default route into the stub area 15. In fact R5 is the only router on area 15 adversing routes into area 15. Since we are not allowed to change R1's configuration, we will leave it this way.

We can also see that R1 got no route to R2's Lo0 IP address.

Does R1 and R2 got an OSPF neighbor relationship?

On R1:

R1#sh ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface
8.7.0.5           1   FULL/BDR        00:00:31    8.7.15.5        FastEthernet0/1

R1 got no neighbor relationship with R2. Lets check on both R1 and R2, if the S1/0 interface is an OSPF interface in area 0.

On R1:

R1#sh ip ospf interface brief 
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Lo0          1     0               8.7.0.1/32         1     LOOP  0/0
Se1/0        1     0               8.7.12.1/24        64    DR    0/0
Fa0/1        1     15              8.7.15.1/24        1     DR    1/1

On R2:

R2#sh ip ospf interface brief 
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Lo0          1     0               8.7.0.2/32         1     LOOP  0/0
Se1/0        1     0               8.7.12.2/24        64    DR    0/0


Both interfaces are configured as area 0 interfaces. Lets check for connectivity between R1 and R2.

On R2:

R2#ping 8.7.12.1


Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 8.7.12.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

R2#


R2 got no connectivity with R1. Lets check interface configuration.

On R2:

R2#show run interface serial 1/0
Building configuration...

Current configuration : 202 bytes
!
interface Serial1/0
 ip address 8.7.12.2 255.255.255.0
 encapsulation frame-relay
 ip ospf 1 area 0
 serial restart-delay 0
 frame-relay map ip 8.7.12.1 102 broadcast
 no frame-relay inverse-arp
end

We can see that the DLCI on the FR mapping is incorrect. Lets fix that and try to check connectivity again.

On R2:

R2(config)#int s1/0
R2(config-if)#no frame-relay map ip 8.7.12.1 102 broadcast
R2(config-if)#frame-relay map ip 8.7.12.1 201 broadcast
R2(config-if)#do ping 8.7.12.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.7.12.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms

Now, lets recheck the OSPF neighbor relationship on R2.

On R2:

R2#sh ip ospf neighbor 

R2#

Still no OSPF neighbor relationship. Lets enable OSPF debugging.

On R2:

R2#debug ip ospf hello 

OSPF hello events debugging is on

R2#

*May 15 16:24:09.279: OSPF: Rcv hello from 8.7.0.1 area 0 from Serial1/0 8.7.12.1

*May 15 16:24:09.283: OSPF: Mismatched hello parameters from 8.7.12.1

*May 15 16:24:09.283: OSPF: Dead R 40 C 120, Hello R 10 C 30  Mask R 255.255.255.0 C 255.255.255.0

R2#

*May 15 16:24:18.391: OSPF: Rcv hello from 8.7.0.1 area 0 from Serial1/0 8.7.12.1

*May 15 16:24:18.395: OSPF: Mismatched hello parameters from 8.7.12.1

*May 15 16:24:18.395: OSPF: Dead R 40 C 120, Hello R 10 C 30  Mask R 255.255.255.0 C 255.255.255.0



We have parameters mismatch between R1 and R2. Lets check R2's  interface OSPF parameters.

On R2:

R2#sh ip ospf interface s1/0
Serial1/0 is up, line protocol is up 
  Internet Address 8.7.12.2/24, Area 0 
  Process ID 1, Router ID 8.7.0.2, Network Type NON_BROADCAST, Cost: 64
  Enabled by interface config, including secondary ip addresses
  Prefix-suppression is enabled
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 8.7.0.2, Interface address 8.7.12.2
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:20
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 0
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0 
  Suppress hello for 0 neighbor(s)

The hello intervals of R1 are like the default ethernet intervals, while R2's hello intervals are like typical WAN interface intervals, and they do not match. We can also notice from the debug that R2 is not sending any OSPF hello messages. Which usually means that R2 is configured as non-broadcast and R1 is configured as broadcast OSPF interface type.


Since we are not allowed to change R1's configuration, lets change R2's hello timer.

On R2:

R2(config)#int s1/0
R2(config-if)#ip ospf hello-interval 10
R2(config-if)#
*May 15 16:28:16.119: %OSPF-5-ADJCHG: Process 1, Nbr 8.7.0.1 on Serial1/0 from LOADING to FULL, Loading Done

Now R2 and R1 have an OSPF neighbor relationship.


Lets check R2's routing table and see what OSPF routes we got there.

On R2:

R2#sh ip route ospf
     8.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O IA    8.7.15.0/24 [110/65] via 8.7.12.1, 00:11:08, Serial1/0
O       8.7.0.1/32 [110/65] via 8.7.12.1, 00:11:08, Serial1/0


We don't see any routes for R1 or R5 interface. And this is expected as routes from non-backbone area will not be advertised to the backbone area.


Since we can't configure R1, the usual textbook solution will be to add a tunnel between R2 and R3 to bypass the troublesome R1, but since we know that R5 has no routes from R1, a tunnel can't be operational. We should find another solution.


The chosen solution here is to add an interface to R3. Not a tunnel interface, but to connect R3 to R2 using FR.


On R2:


R2(config)#int s1/0.23 point-to-point 

R2(config-subif)#ip addr 8.7.23.2 255.255.255.0

R2(config-subif)#ip ospf 1 area 0

R2(config-subif)#frame interface-dlci 203


On R3:

R3(config)#interface s1/0
R3(config-if)#encap frame
R3(config-if)#no frame inver
R3(config-if)#no shut
*May 15 16:43:41.871: %LINK-3-UPDOWN: Interface Serial1/0, changed state to up
*May 15 16:43:52.875: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to up
R3(config-if)#int s1/0.23 point-to-point
R3(config-subif)#ip addr 8.7.23.3 255.255.255.0
R3(config-subif)#ip ospf 1 area 0
R3(config-subif)#frame interface-dlci 302
R3(config-fr-dlci)#
*May 15 16:46:22.363: %OSPF-5-ADJCHG: Process 1, Nbr 8.7.0.2 on Serial1/0.23 from LOADING to FULL, Loading Done


Now lets try to ping again to R2's Lo0 from all routers.

On R1:

R1#ping 8.7.0.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.7.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms

On R3:

R3#ping 8.7.0.2


Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 8.7.0.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

On R5:

R5#ping 8.7.0.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.7.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/12 ms

Success! All routers can ping R2's Lo0.

                                          __ 
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