Task 5.4: from and through AS (is there a difference?)
The requirement of the lab states that AS 400 will not provide transit for traffic coming from AS 54 and its customers that is destined for AS 254.
Now, I can see an as-path match for _254$ providing the first such stipulation, traffic coming from AS 54. But would you not need and as-path match for _254_ to prevent AS 254's customers from transiting AS 254 in to AS 400?
Would blocking the route with a _254$ match be enough to ensure that AS 254's customers don't know about it? If so can you tell me? Unfortunately I'm just not seeing it, although I can imagine it.
Now, I can see an as-path match for _254$ providing the first such stipulation, traffic coming from AS 54. But would you not need and as-path match for _254_ to prevent AS 254's customers from transiting AS 254 in to AS 400?
Would blocking the route with a _254$ match be enough to ensure that AS 254's customers don't know about it? If so can you tell me? Unfortunately I'm just not seeing it, although I can imagine it.
Comments
ip as-path access-list 254 permit _254_
ip as-path access-list 254 permit _254$