2.1 Configure, verify and troubleshoot Inter-VLAN routing

Bit of revision from ICND1 in this one, when a router is making the decision of where to send a packet as multiple options fill up its routing table.

1- Next Hop – If one of the routes that is in the routers routing table has a next hop that the router doesn’t know how to get to it invalidates the route and does not use it.
2- The next item the router considers when seleting a route is route specificity. The more specific a route the more likely it is to be chosen as the elected route. This takes precedence to administrative distance.
3- Administrative distance is the number used to decide which route to trust based on how a route found its way into the routing table (assuming the specificity is the same). Below is a graph of some common Route Sources and their associated Administrative Distances. The lower the Administrative Distance the more preferable the route will be.
4- If the specificity and the administrative distance are both the same then the metric characteristic will be used to break the tie. It’s synonymous with hop count – so the router will choose the route that’s the fewest hops away from its destination.

Route SourceAdministrative Distance
Directly Connected Interface0
Static Route1
EIGRP Summary Route5
External BGP20
Internal EIGRP90
External EIGRP170
Internal BGP200

2.1.a Router on a stick

2.1.b SVI