* * * * *
                                        
                         “The traffic is going where?”
                                        
Ah, nothing like dynamically generated sub-optimal routing. 

Smirk had me install a new router for our T1 customers, and the resulting
changes in network topology were rather amusing. The expected path for
traffic to customer R was “Internet → Core → Edge-02 (the new router) → R”
but instead it went “Internet → Core → Core-02 → Customer S → Edge-02 (over
Customer S' T1 no less!) → R.” 

Ah, it's the multiple paths between the two cores that lower the “cost” for
traffic. The fix was easy enough—bump up the “cost” of Customer S' T1 such
that traffic will prefer a “cheaper” path and not go over Customer S' T1. 


Email Sean Conner at sean@conman.org

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