Subnet Mask in IGP for Loopbacks

Topology :

Configuration :

R1#

interface Serial0/0
 ip address 10.0.12.1 255.255.255.0
router eigrp 100
 network 0.0.0.0
 no auto-summary

router ospf 100
 router-id 11.11.11.11
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

R2#

interface Serial0/0
 ip address 10.0.12.2 255.255.255.0
interface Serial0/1
 ip address 10.0.23.2 255.255.255.0
router eigrp 100
 network 0.0.0.0
 no auto-summary

router ospf 100
 router-id 22.22.22.22
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

R3#

interface Loopback3
 ip address 3.3.3.3 255.255.0.0

interface Loopback33
 ip address 33.33.33.33 255.255.255.248
interface Serial0/0
 ip address 10.0.23.3 255.255.255.0
 clock rate 2000000

router eigrp 100
 network 3.3.0.0 0.0.255.255
 network 10.0.23.0 0.0.0.255
 network 33.33.33.32 0.0.0.7
 no auto-summary

router ospf 100
 router-id 32.32.32.32
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

 Testing :

Related configuration :

R3(config)#do sh int lo33
Loopback33 is up, line protocol is up
  Hardware is Loopback
  Internet address is 33.33.33.33/29

Observe the output carefully :

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 not set
     33.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
O       33.33.33.33/32 [110/129] via 10.0.12.2, 00:21:22, Serial0/0
D       33.33.33.32/29 [90/2809856] via 10.0.12.2, 00:12:11, Serial0/0     3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
O       3.3.3.3/32 [110/129] via 10.0.12.2, 00:21:22, Serial0/0
D       3.3.0.0/16 [90/2809856] via 10.0.12.2, 00:12:11, Serial0/0
     10.0.0.0/24 is subnetted, 2 subnets
C       10.0.12.0 is directly connected, Serial0/0
D       10.0.23.0 [90/2681856] via 10.0.12.2, 00:32:09, Serial0/0

I want to reach 33.33.33.33 which is configured in R3 and this Network is learned by both IGP's EIGRP and OSPF.
So obviously i expect to reach by EIGRP as this is preferred and less AD value than OSPF.

R1#sh ip route 33.33.33.33
Routing entry for 33.33.33.33/32
  Known via "ospf 100", distance 110, metric 129, type intra area  Last update from 10.0.12.2 on Serial0/0, 00:17:52 ago
  Routing Descriptor Blocks:
  * 10.0.12.2, from 32.32.32.32, 00:17:52 ago, via Serial0/0
      Route metric is 129, traffic share count is 1

R2#sh ip route 33.33.33.33
Routing entry for 33.33.33.33/32
  Known via "ospf 100", distance 110, metric 65, type intra area  Last update from 10.0.23.3 on Serial0/1, 00:18:41 ago
  Routing Descriptor Blocks:
  * 10.0.23.3, from 32.32.32.32, 00:18:41 ago, via Serial0/1
      Route metric is 65, traffic share count is 1

Why it did not prefer to take the path by EIGRP ?
Have you noticed the mask information ?

Then you are good to go.

** Always longest match will be preferred first then followed by AD or metric values etc..
** So here OSPF took the advantage of taking / learning this as /32 but EIGRP still took as it is so it is still /29
** obviously OSPF is preferred.

How to fix this ?

Check how OSPF is treating Loopback interface details here :

R3(config)#do sh ip ospf inter l33
Loopback33 is up, line protocol is up
  Internet Address 33.33.33.33/29, Area 0
  Process ID 100, Router ID 32.32.32.32, Network Type LOOPBACK, Cost: 1
  Loopback interface is treated as a stub Host
Check how EIGRP is treating Loopback interface details here :

R3(config)#do sh ip eigrp int l33
IP-EIGRP interfaces for process 100
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Lo33               0        0/0         0       0/1            0           0

** So there is a difference in treatment.
** So to advertise currect subnet mask for Loopbacks there are multiple ways to do this but
simple way is just change the Network type from Loopback to "Point-to-Point"

Solution:

R3(config)#int lo33
R3(config-if)#ip ospf network point-to-point
R3(config-if)#end

And the Routing table update is :

R1#sh ip route 33.33.33.33
Routing entry for 33.33.33.32/29
  Known via "eigrp 100", distance 90, metric 2809856, type internal  Redistributing via eigrp 100
  Last update from 10.0.12.2 on Serial0/0, 00:34:52 ago
  Routing Descriptor Blocks:
  * 10.0.12.2, from 10.0.12.2, 00:34:52 ago, via Serial0/0
      Route metric is 2809856, traffic share count is 1
      Total delay is 45000 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2

R2#sh ip route 33.33.33.33
Routing entry for 33.33.33.32/29
  Known via "eigrp 100", distance 90, metric 2297856, type internal  Redistributing via eigrp 100
  Last update from 10.0.23.3 on Serial0/1, 00:34:39 ago
  Routing Descriptor Blocks:
  * 10.0.23.3, from 10.0.23.3, 00:34:39 ago, via Serial0/1
      Route metric is 2297856, traffic share count is 1
      Total delay is 25000 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1

** So this is just to make sure the behavior of these IGP protocols on how they treat the Network types based on media types. The same follows for 3.3.3.3 also


Happy Labbing  ^_^

Frame-Relay & OSPF with different Network types

  ---------// OSPF & Frame-Relay //----------

Topology Diagram :

=> Interfaces details ( DLCI details can be found in Topology diagram )

R1(config-router)#do sh prot | e do
Global values:
  Internet Protocol routing is enabled
Serial0/0 is up, line protocol is up
  Internet address is 10.0.0.1/24
Loopback11 is up, line protocol is up
  Internet address is 11.11.11.11/32

R2(config-router)#do sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
Serial0/0                  10.0.0.2        YES manual up                    up 
Loopback22                 22.22.22.22     YES manual up                    up 
R2(config-router)#

R3(config-router)#do sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
Serial0/0                  10.0.0.3        YES manual up                    up 
Loopback33                 33.33.33.33     YES manual up                    up 


=> COnfigure and Build L2 & L3 mappings ( Frame-relay connectivity )
=> Now it's a Mesh topology R1 can reach R2 & R3
                            R2 can reach R1 & R3
       R3 can reach R1 & R2

Configuration : 

=> point-to-multipoint

R1(config-router)#do sh run int se 0/0
Building configuration...
Current configuration : 284 bytes
!
interface Serial0/0
 ip address 10.0.0.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 serial restart-delay 0
 clock rate 2016000
 frame-relay map ip 10.0.0.2 102 broadcast
 frame-relay map ip 10.0.0.3 103 broadcast
 no frame-relay inverse-arp
end

R1(config-router)#do sh run | s r o
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

R2(config-router)#do sh run int se 0/0
Building configuration...
Current configuration : 284 bytes
!
interface Serial0/0
 ip address 10.0.0.2 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 serial restart-delay 0
 clock rate 2016000
 frame-relay map ip 10.0.0.1 201 broadcast
 frame-relay map ip 10.0.0.3 203 broadcast
 no frame-relay inverse-arp
end

R2(config-router)#
R2(config-router)#do sh run | s r o
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
R2(config-router)#

R3#sh run int se 0/0
Building configuration...
Current configuration : 264 bytes
!
interface Serial0/0
 ip address 10.0.0.3 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 serial restart-delay 0
 frame-relay map ip 10.0.0.1 301 broadcast
 frame-relay map ip 10.0.0.2 302 broadcast
 no frame-relay inverse-arp
end

R3#sh run | s r o
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
R3#

Check the Routing Table :

R1(config-router)#do sh ip ro os
     33.0.0.0/32 is subnetted, 1 subnets
O       33.33.33.33 [110/65] via 10.0.0.3, 00:06:48, Serial0/0
     22.0.0.0/32 is subnetted, 1 subnets
O       22.22.22.22 [110/65] via 10.0.0.2, 00:06:48, Serial0/0
     10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
O       10.0.0.2/32 [110/64] via 10.0.0.2, 00:06:48, Serial0/0
O       10.0.0.3/32 [110/64] via 10.0.0.3, 00:06:48, Serial0/0
R1(config-router)#

R2(config-router)#do sh ip ro os
     33.0.0.0/32 is subnetted, 1 subnets
O       33.33.33.33 [110/65] via 10.0.0.3, 00:06:08, Serial0/0
     10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
O       10.0.0.3/32 [110/64] via 10.0.0.3, 00:06:08, Serial0/0
O       10.0.0.1/32 [110/64] via 10.0.0.1, 00:06:08, Serial0/0
     11.0.0.0/32 is subnetted, 1 subnets
O       11.11.11.11 [110/65] via 10.0.0.1, 00:06:08, Serial0/0
R2(config-router)#

R3(config-router)#do sh ip ro os
     22.0.0.0/32 is subnetted, 1 subnets
O       22.22.22.22 [110/65] via 10.0.0.2, 00:05:31, Serial0/0
     10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
O       10.0.0.2/32 [110/64] via 10.0.0.2, 00:05:31, Serial0/0
O       10.0.0.1/32 [110/64] via 10.0.0.1, 00:05:31, Serial0/0
     11.0.0.0/32 is subnetted, 1 subnets
O       11.11.11.11 [110/65] via 10.0.0.1, 00:05:31, Serial0/0
R3(config-router)#

Testing / Reachability :
R1(config-router)#do ping 10.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/22/48 ms
R1(config-router)#do ping 10.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/24/56 ms
R1(config-router)#

R2(config-router)#do ping 10.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/24/52 ms
R2(config-router)#do ping 10.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/17/48 ms
R2(config-router)#

R3#ping 10.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/20/56 ms
R3#ping 10.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/23/68 ms
R3#

=> So things are working as expected till now. Life is good.
=> It's time to play now by changing the Network type to watch a big game here.
   There lies the tricks and concept behind the DR/BDR election process, how much it is dependent and how to tweak the parameters of network types & interface natural behavior to participate in Election process.
   It's quite natural that Election process will happen per situation and necessary only for those interface types ( Based on Media types )

 -----// point-to-Point //--------

R1(config-if)#ip ospf network point-to-point
R1(config-if)#
*Mar  1 02:06:42.187: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar  1 02:06:42.191: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
R1(config-if)#

=> See the above reaction the movement we change the network type, they are not happy and walkout from neighborship. The reason behind is because of Hello & Dead timer value changes

Let us compare now :

R1(config-if)#do sh ip os int se 0/0
Serial0/0 is up, line protocol is up
  Internet Address 10.0.0.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

R2#sh ip ospf interface se 0/0
Serial0/0 is up, line protocol is up
  Internet Address 10.0.0.2/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_MULTIPOINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5

=> Hope you got the point here, both the interface types have mismatch in Hello & Dead timer values.
=> So can't agree each other, this is very important to form Neighborship. So i just matched those values manually here

R1(config-if)#ip os hello-interval 30
R1(config-if)#ip os dead-interval  120

R1(config-if)#
*Mar  1 02:27:12.575: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset
*Mar  1 02:27:13.131: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from LOADING to FULL, Loading Done
*Mar  1 02:27:22.871: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset
*Mar  1 02:27:27.915: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from LOADING to FULL, Loading Done
*Mar  1 02:27:29.647: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset
*Mar  1 02:27:29.815: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from EXCHANGE to DOWN, Neighbor Down: Adjacency forced to reset
*Mar  1 02:27:30.115: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from LOADING to FULL, Loading Done

=> Now they just come back and go down, so still stability is not there ( I need to research more on this )

Debug :

R1(config-if)#do deb frame packet
Frame Relay packet debugging is on
R1(config-if)#
*Mar  1 02:32:12.571: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from F                                                                 ULL to DOWN, Neighbor Down: Adjacency forced to reset
*Mar  1 02:32:14.971: Serial0/0(i): dlci 103(0x1871), pkt type 0x800, datagramsi                                                                 ze 68
*Mar  1 02:32:14.979: Serial0/0: broadcast search
*Mar  1 02:32:14.983: Serial0/0: Broadcast on DLCI 103  link 7
*Mar  1 02:32:14.983: Serial0/0(o): dlci 103(0x1871), pkt type 0x800(IP), datagr                                                                 amsize 128
*Mar  1 02:32:14.987: Serial0/0(o): dlci 102(0x1861), pkt type 0x800(IP), datagr                                                                 amsize 128
*Mar  1 02:32:15.023: broadcast dequeue
*Mar  1 02:32:15.023: Serial0/0(o):Pkt sent on dlci 103(0x1871), pkt type
0x800(IP), datagramsize 128
*Mar  1 02:32:15.023: broadcast dequeue
*Mar  1 02:32:15.023: Serial0/0(o):Pkt sent on dlci 102(0x1861), pkt type
0x800(IP), datagramsize 128

-----// point-to-multipoint nonbroadcast //--------

R1(config-if)#ip ospf network point-to-multipoint non-broadcastR1(config-if)#
*Mar  1 02:39:38.115: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar  1 02:39:38.119: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
R1(config-if)#
*Mar  1 02:39:42.671: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from LOADING to FULL, Loading Done
*Mar  1 02:39:52.931: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0/0 from LOADING to FULL, Loading Done
R1(config-if)#

R1(config-if)#do sh ip os neigh
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           0   FULL/  -        00:01:50    10.0.0.2        Serial0/0
3.3.3.3           0   FULL/  -        00:01:39    10.0.0.3        Serial0/0
R1(config-if)#
R1(config-if)#
R1(config-if)#
R1(config-if)#do ping 22.22.22.22
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 22.22.22.22, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/20/56 ms
R1(config-if)#do ping 33.33.33.33
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 33.33.33.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/25/56 ms
R1(config-if)#

=> Things are still working because we manually done the mapping job in L2 level, so there is no reachability issue by this.

=> Another fair game, now i am going to configure " ip ospf network point-to-multipoint non-broadcast" on R2
-------------
Before :

R2(config-if)#do sh ip os neigh
Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/  -        00:01:56    10.0.0.3        Serial0/0
1.1.1.1           0   FULL/  -        00:01:55    10.0.0.1        Serial0/0
R2(config-if)#
R2(config-if)#
R2(config-if)#ip ospf network point-to-multipoint non-broadcastR2(config-if)#
*Mar  1 02:47:36.151: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar  1 02:47:36.159: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1.1 on Serial0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
R2(config-if)#
R2(config-if)#do sh ip os neigh

It will tear down the connections and come's back only for R3, because R3 is still "Broadcast" and R1 will NOT be neighbor any more. Because R1 also configured "Nonbroadcast"

R2(config-if)#do sh ip os neigh
R2(config-if)#
*Mar  1 02:48:02.631: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0/0 from LOADING to FULL, Loading Done

After some time : Still no connectivity to R1

R2(config-if)#do sh ip os neigh
Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           0   FULL/  -        00:01:57    10.0.0.3        Serial0/0
R2(config-if)#
BUT...BUT....i am still able to ping "R1"
How? because we are done with manual bindings like below config shows.

R2(config-if)#do ping 10.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/31/96 ms
R2(config-if)#do ping 11.11.11.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.11.11.11, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/28/88 ms
R2(config-if)#do sh run int se 0/0
Building configuration...
Current configuration : 298 bytes
!
interface Serial0/0
 ip address 10.0.0.2 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint non-broadcast
 serial restart-delay 0
 clock rate 2016000
 frame-relay map ip 10.0.0.1 201 broadcast
 frame-relay map ip 10.0.0.3 203 broadcast no frame-relay inverse-arp
end

R2(config-if)#
------------

=> In some situation we need to use 'Neighbor <ip>' command to tell the OSPF process whom to contact, the best practice is to configure on HUB Router rather Spoke.
=> HUB Router know to provide reachability with other neighbors, this is simple and no confusion to process.


Happy Labbing ^_^

Bidirectional Forwarding Detection for OSPF

This is some thing we don't use in Infra but i would like to see what is this about :

Bi-directional Forwarding Detection (BFD) provides rapid failure detection times between forwarding engines, while maintaining low overhead. It also provides a single, standardized method of link/device/protocol failure detection at any protocol layer and over any media.

Using BFD as Part of a Network Redundancy Plan :

BFD can be an important part of an overall network redundancy plan, including other Cisco innovations like Nonstop Forwarding (NSF) and the Hot Standby Router Protocol (HSRP). BFD should be deployed in those sections of the network where subsecond failure detection is required, but cannot be provided by traditional Layer 2 mechanisms. Being said that it need Layer 3 Routing in place.

Configration :

R1#sh run | s r o
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 12.1.1.1 0.0.0.0 area 0
 bfd all-interfaces

R1#sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            12.1.1.1        YES manual up                    up 

R2#sh run | s r o
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 12.1.1.2 0.0.0.0 area 0
 bfd all-interfaces

R2#sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            12.1.1.2        YES manual up                    up
R2#

Testing :

R1#sh ip ospf interface fa 0/0
FastEthernet0/0 is up, line protocol is up
  Internet Address 12.1.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State BDR, Priority 1, BFD enabled

R2#sh ip ospf int fa 0/0
FastEthernet0/0 is up, line protocol is up
  Internet Address 12.1.1.2/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State DR, Priority 1, BFD enabled  Designated Router (ID) 2.2.2.2, Interface address 12.1.1.2

Thanks for reading :)

Q&A time ::

OSPF Virtual-link Concept

I just simulated simple OSPF virtual-link concept.

Objective :  Creating Virtual link taking "Area 2" as transit. So Area 1 Networks are reachable from Backbone and RTR-B LSDB contains non backbone area information which is passible by using Virtual-links configuration.

Configuration :

RTR-A

RTRA#sh run | s r o
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 area 2 virtual-link 2.2.2.2
 network 11.11.11.1 0.0.0.0 area 1
 network 12.12.12.1 0.0.0.0 area 2

RTRA#sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            12.12.12.1      YES manual up                    up
FastEthernet0/1            unassigned      YES unset  administratively down down
Loopback0                  11.11.11.1      YES manual up                    up

RTR-B :

RTRB#sh run | s r o
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 area 2 virtual-link 1.1.1.1
 network 12.12.12.2 0.0.0.0 area 2
 network 22.22.22.22 0.0.0.0 area 0


RTRB#sh ip int brie | e un
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            12.12.12.2      YES manual up                    up
Loopback0                  22.22.22.22     YES manual up                    up

Testing :

RTR-A


RTRA#sh ip ospf virtual-links
Virtual Link OSPF_VL1 to router 2.2.2.2 is up
  Run as demand circuit
  DoNotAge LSA allowed.
  Transit area 2, via interface FastEthernet0/0, Cost of using 10
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:05
    Adjacency State FULL (Hello suppressed)
    Index 1/2, 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

RTRA#ping 22.22.22.22
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 22.22.22.22, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/48/88 ms

RTR-B:

RTRB#ping 11.11.11.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.11.11.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/45/84 ms


RTRB#sh ip route ospf
     11.0.0.0/32 is subnetted, 1 subnets
O IA    11.11.11.1 [110/11] via 12.12.12.1, 00:08:56, FastEthernet0/0
OSPF LSDB & Neighbor details :

RTRA#sh ip ospf neig
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           0   FULL/  -           -        12.12.12.2      OSPF_VL1
2.2.2.2           1   FULL/DR         00:00:38    12.12.12.2      FastEthernet0/0

RTR-A:

RTRA#sh ip ospf data
            OSPF Router with ID (1.1.1.1) (Process ID 1)
                Router Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         260         0x80000004 0x00618D 1
2.2.2.2         2.2.2.2         1     (DNA) 0x80000004 0x00A1DE 2
                Summary Net Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum
11.11.11.1      1.1.1.1         468         0x80000001 0x00DD38
12.12.12.0      1.1.1.1         468         0x80000001 0x000C02
12.12.12.0      2.2.2.2         616   (DNA) 0x80000002 0x00EB1D
                Router Link States (Area 1)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         468         0x80000003 0x00C044 1
                Summary Net Link States (Area 1)
Link ID         ADV Router      Age         Seq#       Checksum
12.12.12.0      1.1.1.1         468         0x80000001 0x000C02
22.22.22.22     1.1.1.1         257         0x80000001 0x00E1F3
                Router Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         261         0x80000005 0x003E8F 1
2.2.2.2         2.2.2.2         262         0x80000004 0x0002C3 1
                Net Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum
12.12.12.2      2.2.2.2         628         0x80000002 0x00FF02
                Summary Net Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum
11.11.11.1      1.1.1.1         469         0x80000001 0x00DD38
22.22.22.22     2.2.2.2         878         0x80000002 0x005D7D

RTR-B:

RTRB#sh ip route ospf
     11.0.0.0/32 is subnetted, 1 subnets
O IA    11.11.11.1 [110/11] via 12.12.12.1, 00:08:56, FastEthernet0/0

RTRB#sh ip ospf data
            OSPF Router with ID (2.2.2.2) (Process ID 1)
                Router Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         1     (DNA) 0x80000004 0x00618D 1
2.2.2.2         2.2.2.2         556         0x80000004 0x00A1DE 2
                Summary Net Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum
11.11.11.1      1.1.1.1         208   (DNA) 0x80000001 0x00DD38
12.12.12.0      1.1.1.1         208   (DNA) 0x80000001 0x000C02
12.12.12.0      2.2.2.2         1171        0x80000002 0x00EB1D
                Router Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         556         0x80000005 0x003E8F 1
2.2.2.2         2.2.2.2         556         0x80000004 0x0002C3 1
                Net Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum
12.12.12.2      2.2.2.2         921         0x80000002 0x00FF02
                Summary Net Link States (Area 2)
Link ID         ADV Router      Age         Seq#       Checksum
11.11.11.1      1.1.1.1         765         0x80000001 0x00DD38
22.22.22.22     2.2.2.2         1172        0x80000002 0x005D7D

Q & A time

- I can explain if you have any questions and thanks for reading :)

OSPF - Basic Peering

OSPF and Frame Relay

1.  Match Network types or Interface types 

              - Frame -Relay Interface type ::   Physical , Multipoint, Point-2-Point
              - OSPF :: 5 Network types
 2. Timers won't match if Interfaces types are different.
 3. Remmeber that Broadcast and non-broadcast try to elect DR/BDR.
      - HUB must be DR
 4. Don't forget the "broadcast" statement if you are using frame maps.