A default route is considered a gateway of last resort; meaning all ip packets that don't have a match in the routing table of a router will be forwarded to the default route.
An ultimate route is a route in the routing table of a router that indicates both the next hop ip address and the exit interface.
Parent route has a exit interface, but an Ultimate route has "No Exit Informationint the top is one of the other answer. but i dont want to change anything. i just want to answer that parent route has no exit interface but the ultimate route has exit interface.
It is the difference between walking and swimming.
Default route
When you have routing enabled then you need default route (also calleddefault network or Gateway of Last Resort). You do not need default routeif you don't use routing. For example if you just have one router in your network there is no need for default route. When you have more than one router in a network you need default route.Note: If you connect to WAN (Internet) you need default route. The default route allows connection with Internet. If you are not using WAN and have one router than there is not need for default route but in these days everyone connects to the Internet so most likely your router has default route. When using router to connect to the Internet using DHCP this happens automatically so there will no need to configure default route manually. If you need to manually set default route then use the commands IP default-network or IP route 0.0.0.0 0.0.0.0 .More info can be found at Cisco's site - see the related link below.
ip default gateway
"Ultimate route" effectively means the route ultimately resolved after any recursive look-ups if necessary. A route with an exit interface
The administrative distance of a default route is typically 1. This means that it is considered the most reliable and preferred route for forwarding traffic when no other more specific route is available in the routing table.
default
You actually cannot make a routing table based on next hop (alone). Next hop is the default gateway ands is always a required part of a route. A route always contains three fields: Network ID, Cost, Next hop.
Post is towards the center of the field, flag is toward the sideline.
The route includes an exit interface
automatically assign an ip address