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I have heard that the BGP routes exchanged between the routers do not necessarily mean that the actual data path will follow the specified routes. How can the data path and control path be different in BGP-based routing?

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  • What do you mean? The control plane runs BGP and instructs the data plane how and where to forward data. Whether any paths conveyed via BGP make it into the FIB or not doesn't matter.
    – Zac67
    Jul 24, 2023 at 10:03
  • If I see BGP routes that are collected by collectors (eg. Routeviews), can I say this is the exact path followed? Jul 24, 2023 at 10:11
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    Basically, no. BGP is just one source for routes among others.
    – Zac67
    Jul 24, 2023 at 10:53
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    Routing protocols do not route packets. They exchange routing information.
    – Ron Maupin
    Jul 24, 2023 at 12:51

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How can the data path and control path be different in BGP-based routing?

I think there's a misunderstanding. BGP is run by the control plane. The control plane then decides which routes are actually used (in FIB) and which aren't. That decision depends on the router configuration: route metrics, filters and precedence. The actual routing then takes place in the data plane.

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