This topic is to discuss the following lesson:
Hello Rene,
First, thanks for the excellent course on Traffic-eng.
I’m a bit confused about the routing once you enable autoroute, specially for the loopback tailend:
i L2 6.6.6.6 [115/30] via 6.6.6.6, 00:00:23, Tunnel1
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Knowing that to establish the tunnel, we’re using the “destination 6.6.6.6”, isn’t there some recursive routing issue ?
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what about periodic refresh of Path messages, will they go via the IGP path or Tunnel path ?
Kind regards,
Naoufal
Hello Naoufal
Regarding your first question, it might seem like there could be a recursive routing issue, but in fact, it’s not the case. When you configure a tunnel with destination 6.6.6.6, it means that the tunnel is destined for 6.6.6.6. However, the routing of the tunnel itself depends on the routing table. So, it’s not a recursive routing because the tunnel is not routed through itself. Instead, it uses the TE tunnel path to reach the destination. Once the tunnel is up and you enable autoroute, the traffic to 6.6.6.6 will be routed via the tunnel.
Take a look at this NetworkLessons note on the topic of MPLS-TE Path Message Behavior that explains this in more detail.
For your second question, the periodic refresh of the Path messages will indeed go via the tunnel path, but they won’t be sent within the tunnel itself. This must take place because it is these messages that establish and maintain the path that the tunnel must follow. Does that make sense?
I hope this has been helpful!
Laz
Hello Laz,
Many thanks for the explanation, very clear now !
Cheers
Naoufal
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