Cisco CCNP / BSCI Examination Tutorial: Establishing And Troubleshooting OSPF Electronic Links

Knowing when and how to create an OSPF virtual link is an essential skill for BSCI and CCNP examination success, as well as how important it may be on your own work! As a CCNA and CCNP prospect, you know the idea of virtual links, so let us have a look at how-to manage a virtual link, together with some real-world tips that many CCNA and CCNP study courses leave out!

In this setting, no modem with the interface in Area 4 has a physical interface in Area 0. This implies a logical relationship to Area 0, a virtual link, must be created.

Within the following example, R1 and R-3 are adjacent and both have interfaces in Area 0. R4 has an adjacency with R3 via Area 34, but R4 advertising its loopback 4.4.4.4 in-to OSPF and is has no physical interface in Area 0. R1 doesn’t have the route to that loopback.

R1#show ip option ospf

6.0.0.0/32 is subnetted, 1 subnets

O 6.6.6.6 [110/11] via 10.1.1.5, 01:05:45, Ethernet0

172.23.0.0/27 is subnetted, 1 subnets

O IA 172.23.23.0 [110/74] via 172.12.123.3, 00:04:14, Serial0

7.0.0.0/32 is subnetted, 1 subnets

O 7.7.7.7 [110/11] via 10.1.1.5, 01:05:45, Ethernet0

To eliminate this, a virtual link will soon be built between R-3 and R4 through Area 34. The area by which the virtual link is built, the transportation area, cannot be a stub area of any sort.

R4( config )#router ospf 1

R4( config-router )#area 3-4 virtual-link 3.3.3.3

R3( config )#router ospf 1

2d07h: %OSPF-4-ERRRCV: Received broken packet: mismatch area ID, from spine area must be virtual-link but not found from 172.23.23.4, Ethernet0

R3( config )#router ospf 1

R3( config-router )#area 3-4 virtual-link 4.4.4.4

R3( config-router )#^Z

2d07h: %OSPF-5-ADJCHG: Process 1, Nbr 4.4.4.4 on OSPF_VL0 from LOADING to FULL, Loading Done

A few facts worth noting… the electronic link control uses the distant device’s RID, not necessarily the IP-ADDRESS on the software that’s in-the transportation area. Also, do not be worried about that error message you see in the result from R3 that’s normal and you’ll see it until you finish making the virtual link.

Always ensure the personal link with show internet protocol address ospf virtual-link. If you have configured it precisely, the VL should show up in a matter of seconds.

R3#show ip address ospf virtual-link

Personal Link OSPF_VL0 to router 4.4.4.4 is up

Work as need signal

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Transportation area 34, via screen Ethernet0, Cost of using 1-0

Transmit Delay is 1 sec, State POINT_TO_POINT,

Timer intervals configured, Hello 1-0, Dead 40, Wait 40, Retransmit 5

Hello due in 00:00:00

Adjacency State FULL (Hello suppressed)

Index 2/4, retransmission queue size 1, quantity of retransmission 1

First 0x2C8F8E( 15 )/0x0( 0) Next 0x2C8F8E( 15 )/0x0( 0)

Last retransmission scan period is 1, maximum is 1

Last retransmission scan time is 0 msec, optimum is 0 msec

Url State retransmission due in 3044 msec

Virtual links are actually easy to manage, but for some reason they appear to intimidate people. It’s my knowledge that the error message highlighted in R3’s production above causes lots of stress, but the only factor that message means is that you are not done making the virtual link however.

There are three main misconfigurations that cause 99% of personal link setup issues:

Using the wrong OSPF RID value

Wanting to work with a stub area while the flow area

Failure to arrange link authentication on the electronic link when Area 0 is running authentication

That last one will be the one that gets forgotten! A virtual link is actually an extension of Area 0, and if Area 0 is working link certification, the virtual link should be constructed for it too. Look closely at the facts. This stylish sponsors essay has a myriad of commanding suggestions for where to consider it. Do not stress when you see the error message on the 2nd hub you arrange with all the virtual link, and you’ll prepare yourself for just about any virtual link situation on the work or within the CCNA / CCNP assessment area!. Should you fancy to identify supplementary resources on guide to http://vitaldesigngroup.com/product-packaging-design, there are many online libraries you should think about investigating.