SD-WAN strategy and dynamic routing
In our SD-WAN Solution, traffic steering decisions are taken primarily by the originating sites (that is, by the SD-WAN node behind which a session in question has originated). But there are use cases when it is convenient to base the traffic steering decision on the information received from the dynamic routing (that is, on the information advertised by other sites, either SD-WAN sites or not!).
Route-Tags provide a useful mechanism for this integration. The idea is simple:
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Route-tags are assigned locally on the SD-WAN node to the incoming routes, based on a user-defined criteria. For example, all the routes having a certain BGP community can be marked with a certain route-tag.
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This route-tag, in turn, can be used as a matching criteria in an SD-WAN rule.
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This way, we can use dynamic routing to signal certain site properties to the the SD-WAN nodes, that will use this information to choose the best suitable traffic steering stretegy.
Let us stress again that this signaling can come either from within the SD-WAN network (from another SD-WAN node) or from outside. We have already seen in the Hub-to-Edge SD-WAN section how we can advertise our preferences outside of the SD-WAN network. Here we show the signaling in the opposite direction: