Lab 3 Ticket 5

Hey all,

The solution guide os quite different from my solution:

INE Q)ensure traffic between R1 & R5 takes the optimal (direct) path.

INE A)The incorrect Frame Relay mapping on R1 prevents the OSPF adjacency from
coming up.

R1:
interface Serial 0/0.15
frame-relay map ip 10.1.0.11 105 broadcast
no frame-relay map ip 10.1.0.10 10
5

 

I disagree, yes the frame relay link need fixing, is did this a different way:

!!!R1
interface serial 0/1/0.15
 no frame-rel map
ip 10.1.0.10 105
 frame0relay interface-dlci 105

This was only half the puzzle, the question says take the optimal (direct) path. to me thats over this frame-relay link right?

 

So with the links fixed the routes to R5 are still via the best path, which is over the fastethenet link (R5-S1-R1)

Rack1R1#show ip route 10.1.5.5
Routing entry for 10.1.5.5/32
  Known via "ospf 1", distance 110, metric 3, type intra area
  Last update from 10.1.0.13 on FastEthernet0/0, 00:00:00 ago
  Routing Descriptor Blocks:
  * 10.1.0.13, from 10.1.5.5, 00:00:00 ago, via FastEthernet0/0
      Route metric is 3, traffic share count is 1

This is because the default serial cost is 64:

Rack1R1#show ip ospf interface serial 0/1/0.15 | include Cost
  Process ID 1, Router ID 10.1.1.1, Network Type POINT_TO_POINT, Cost: 64

Whereas the Q is asking for the direct path, so to achive this i tweeked the link costs:

!!R1 & R5
 int ser x/y/z.xxx
  ip ospf cost 1

Now we use the direct path as requested.

Rack1R1#show ip route 10.1.5.5
Routing entry for 10.1.5.5/32
  Known via "ospf 1", distance 110, metric 2, type intra area
  Last update from 10.1.0.11 on Serial0/1/0.15, 00:00:05 ago
  Routing Descriptor Blocks:
  * 10.1.0.11, from 10.1.5.5, 00:00:05 ago, via Serial0/1/0.15
      Route metric is 2, traffic share count is 1

 

So this could go two ways, either I am correct or infact the statement "ensure traffic between R1 & R5 takes the optimal (direct) path" should omint the (direct) keyword, as this contridicts the 'optimal path'?

 

Cheers all, I now open this up for assasination! (I accept my faults in the form of typos.. :)

Sam.

Comments

  • INE Q)ensure traffic between R1 & R5 takes the optimal (direct) path.

    INE A)The incorrect Frame Relay mapping on R1 prevents the OSPF adjacency from
    coming up.

    R1:
    interface Serial 0/0.15
    frame-relay map ip 10.1.0.11 105 broadcast
    no frame-relay map ip 10.1.0.10 10
    5

     

    I disagree, yes the frame relay link need fixing, is did this a different way:

    !!!R1
    interface serial 0/1/0.15
     no frame-rel map
    ip 10.1.0.10 105
     frame0relay interface-dlci 105

    I don't have the full config and questions in front of me, but I think that their solution here is better, and is closer to what you will be expected to do in the real exam. The proctor said words to the effect of: "This was a network built by a CCIE, but a CCNA has been in there and broken a few things. You should be looking for a few quick changes, not changing features or making significant changes. If you find yourself adding several lines of config, you've probably gone down the wrong path." 

    So when you look at a Frame-Relay misconfiguration, what's the most likely thing that you need to do? Fix a single digit typo, or remove a whole line and put something different in? The simplest (and usually correct) answer is to fix the typo.

    It's in the same class as broken OSPF authentication, or a misconfigured ACL. Do you fix the configuration, or remove authentication/the ACL? You fix the existing config.

    Of course, there are scenarios where you might have a perfectly valid alternative configuration, that works, and doesn't break restrictions. But given a choice, go for the simplest answer.

  • regardless of how we fix frame-relay (i used ine way btw) i agree that the ticket is not solved without changing the ospf cost.

    fixing frame relay bring the adj up, but still it won't use that link unless you change the cost

  • Yes, the ospf cost was the key missing data from the SG :)

    Glad you found the same issue.

     

    The Frame-relay is neither here nor there, as long as it works. Theres solution howver does not achive optimal routing ;)

     

    Sam.

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