What I have read:
For routing basics:
Route Selection in Cisco Routers.pdf
Administrative Distance.pdf
Configuring Cisco Express Forwarding - CEF.pdf
For LB basics:
How Does Load Balancing Work.pdf
Load Balancing with CEF.pdf
The main ideas, as I understand:
1. As soon as a router has 2 (up to 6) routes to the same destination (host or subnet) with the same metric it begins to use Load Balancing.
2. There are 2 ways of LB: per packet and per destination. The first is clear, the second means all traffic\sessions to the same host will go via one and always the same line.
3. LB also depends on the switching mode: FastS (destination based), ProcessS (per packet) or CEF/dCEF (support both). As I understand, the difference is in the way how destination based LB work: in case of CEF mode lines are balanced not just by destination, but by the pair [source ip - dest ip], unlike FS which sends traffic from any source to the same destination via the same line.
4. Recently CEF mode is used by default on most part of routers (using last IOS versions) and by default destination based LB is activated (it is less heavy for routers CPU and memory, but potentially less effective. The latter depends on the quantity of used destinations and equality of data flows: more they are - more effective is LB).
Are these statements correct? If not, please comment mistakes.
Now my questions (the ones I remember, later I may ask some more):
1. In case of destination based LB, if we have routes to a whole subnet, and we have traffic to 2 hosts from that subnet, do we get LB, or any host within the same subnet would be assumed as the same destination?
