The best course is the longest match course to the objective IP address. The course query process coordinates the objective IP address with the course accessible in the directing table and picks the longest match course as sending course.
To coordinate the objective IPv4 address of a bundle with the courses in the directing table; the base number of extreme left pieces should match between the IPv4 address of the parcel and the course in the steering table.
The switch fined the best course in the steering table for the bundle utilizing the subnet cover. The information parcel never contains the subnet cover in the bundle header.
The best course is the longest match or most prominent number comparable extreme left pieces. The figure beneath delineates the greatest pieces match, which is the best course for the parcel.
Assuming the switch gets a bundle bound for 172.16.2.100. The switch has three potential courses for the parcel: 172.16.0.0/16, 172.16.1.0/24 and 172.16.2.0/24. Look it the table above in the figure to comprehend the longest matches steering process.
172.16.2.0/24 has the longest match; so the switch has chosen this course as the best course and advances the bundle to Ethernet 1/1. For any of these courses to be viewed as a match there should be essentially the quantity of matching pieces showed by the subnet cover of the course.
Directing Table Terms
The Cisco IP directing table is a various leveled structure that is utilized to accelerate the query interaction while finding courses and sending parcels. Inside this design, the order incorporates:
- Extreme course
- Level1 course
- Level1 parent course
- Level2 youngster courses
Extreme Route
This course contains either a next-jump IPv4 address or a leave interface. Straightforwardly associated courses progressively scholarly courses, and neighborhood courses are additionally extreme courses. The figure beneath shows a definitive courses.
Level 1 Route
The course that is equivalent to a subnet veil or not exactly the classful cover of the organization address. The wellspring of the level 1 course can be a straightforwardly associated network, static course, and furthermore a dynamic directing convention. Hence, a level 1 course is likewise a definitive courses. The kind of level 1 course included:
Network highway A course that has subnet cover equivalent to the classful organization is called network course.
Default course This is a static course for the bundle whose objective isn’t known to the switch. The location of the default static course is 0.0.0.0/0.
Supernet course This course with network address with a maskless than the classful veil.
Level 1 Parent Route
Level 1 parent course is a level 1 organization course that is subnetted. A parent course can never be an extreme course. The figure underneath delineates the level 1 parent course featured.
Level 2 Child Route
This is a subnet of a classful organization address. As delineated in Figure 1, a level 1 parent course is a level 1 organization course that is subnetted. A level 1 parent courses contain level 2 kid courses, as displayed in the Figure beneath.
There are two levels 2 youngster course for level 1 parent course 10.0.0.0 and three levels 2 kid course for level 1 parent course 172.16.0.0. The wellspring of a level 2 course can be a straightforwardly associated network, a static course, or a powerfully scholarly course. Level 2 youngster courses are likewise extreme courses.
Course Lookup Process
At the point when a switch gets a parcel on a connection point, the switch analyzes the header of the bundle and distinguishes the objective IPv4 address, and continues through the switch query process.
Step-1
The switch inspects level 1 course, as well as organization courses and supernet courses; for the best coordinate with the objective location of the IP bundle.
Assuming the best match is a level 1 course, extreme course, or supernet course then the bundle is forward to the objective utilizing the best match course.
On the off chance that the best match is a level 1 parent course, proceed to the subsequent stage.
Step-2
The switch looks at level 2 kid courses of the level 1 parent course for the best match.
Assuming there coordinate with a level 2 kid courses found, the switch advances the parcel to the objective utilizing this course.
On the off chance that no coordinate is found with any of the level 2 youngster courses, proceed to the subsequent stage.
Step-3
the switch begins query best match in level 1 supernet courses in the directing table, including the default course.
Assuming there is currently a more modest coordinate with a level 1 supernet or default courses; the switch utilizes that course to advance the parcel.
On the off chance that a coordinate to the objective not found with any course in the steering table, the switch drops the parcel.
