Traceroute behaviour in this scenario

[UP82]

Hi! 

I have the following scenario: 3 blue routers are connected in Area 100 OSPF and the two edge router (the blue router on the left and the blue router on the right) have also one interface in Area 0 OSPF and are connected by a link in a VPLS.  Later i simulated a fault on a link as shown in the following figure and i tried to perform a traceroute on the edge left blue router towards 172.16.80.2

In the first attempt i obtained:

1    172.16.200.2

2     *  *  *

3     *   *  *  

4     *   *  *  

5     *   *   * 

6    172.16.80.1

In the second attempt i obtained :

1  172.16.200.2

2 172.16.80.1

Why in the first attempts the output shows the asterisks and in the second attempts it isn't shown? and why in the first attempt it is shown 6 hop?

Thanks 

Paolo 

[Larry Sullivan]

How soon after the link fault did you run the trace? 

[Dennis Mink]

LOL. I was gonna ask the exact same thing. If you tested straight after yiou downed the link, it could be convergence of the routing table was still taking place and you were testing against that. in your second attempt your routing table has most likely converged and you got a correct response

[UP82]

Hi! 

Thanks for your answer,

i was also thinking about traffic black holing due to time of reconvergence of OSPF or OSPF-LDP time of synchronization.....i waited few second (2 or 3).

Tomorrow I will repeat the test waiting more and i let you know.

Thanks

Paolo