Forwarding Modes on Cisco Router

How to choose the best router switching path for your network
document ID 13706
two types of forwarding

prosess switching

interrupt context switching

Process forwarding – looking up routing table every forwarding

Interrupt swithing

Divided into fast switching,optimum switching  and cisco express forwarding

Process switching: show ip route {prefix} , " * "available pointer,

Data is transferred according to which load balance type is using. It takes effect when looking up routing table

3-----------------------1---------------------------2----|2.2.2.2

R1上sh ip route 2.2.2.0

* 12.1.1.2
      Route metric is 0, traffic share count is 1 the balancing of load

Only look up the caches .show ip cache ,router 1.2.3 disable IP CEF to enable this feature.
Prefix/Length           Age       Interface       Next Hop
2.2.2.2/32              00:00:08 Serial1/0       12.1.1.2

Caching once for forwarding many times.
how can we pass through cache? Clearing ip cache will trigger process forwarding(only for the first time)

Routing pointer will change every time looking up routing table.

traffic share count {NO.} "

how can we keep process switch  all the time? How do we run it on 12.3 ios above?
no ip cef       to change fast-switch
if)#no ip route-cache   to change process switch

● per packet loadbalancing
process switch only can be per package! Why ? because of "traffic share count is 1"

3--------------------------1---------------------------------------------2--------------|2.2.2.2
                                     fa0/0____________________fa0/0

Assuming the ratio between seria and fastethernet is 3:1

So, the first package will go to Ethernet port, then second, third and fourth … will go to series port.

but when we ping 5 packages, things will be .!!!! because the first package on FA0/0  is encapsulation failed.

● per destinations loadbalancing
fast-switch only can be per-package load-balancing

Enable ip route-cache

Enable ip cef

Won’t generate CACHE (CEF FIB)
ip cef       sh ip cef

Adjacency table includes data link level information  with ARP,

show adjcency detail

IP       Serial1/1                 point2point(5)
                                   0 packets, 0 bytes
                                   0F000800
                                   CEF   expires: 00:02:13
                                         refresh: 00:00:08
                                   Epoch: 0
IP       FastEthernet0/0           192.168.1.2(14)
                                   0 packets, 0 bytes
                                   CC020F6C0000CC01097C00000800 / /  destination MAC,source MAC ,TYPE
                                   ARP        03:54:05
                                   Epoch: 0
CEF?

16 channels for loadbalancing
invisible command:
show ip cef {prefix} internal

#sh ip cef 2.2.2.2 internal
2.2.2.2/32, version 14, epoch 0, per-destination sharing
0 packets, 0 bytes
via 12.1.1.2, 0 dependencies, recursive
    traffic share 1
    next hop 12.1.1.2, Serial1/0 via 12.1.1.0/24
    valid adjacency
via 192.168.1.2, 0 dependencies, recursive
    traffic share 1
    next hop 192.168.1.2, FastEthernet0/0 via 192.168.1.2/32
    valid adjacency

0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
           internal 0 packets, 0 bytes
Load distribution: 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 (refcount 1)

Hash OK Interface                 Address         Packets
1     Y   Serial1/0                 point2point           0
2     Y   FastEthernet0/0           192.168.1.2           0
3     Y   Serial1/0                 point2point           0
4     Y   FastEthernet0/0           192.168.1.2           0
5     Y   Serial1/0                 point2point           0
6     Y   FastEthernet0/0           192.168.1.2           0
7     Y   Serial1/0                 point2point           0
8     Y   FastEthernet0/0           192.168.1.2           0
9     Y   Serial1/0                 point2point           0
10    Y   FastEthernet0/0           192.168.1.2           0
11    Y   Serial1/0                 point2point           0
12    Y   FastEthernet0/0           192.168.1.2           0
13    Y   Serial1/0                 point2point           0
14    Y   FastEthernet0/0           192.168.1.2           0
15    Y   Serial1/0                 point2point           0
16    Y   FastEthernet0/0           192.168.1.2           0

How to check current channel for load balancing, invisible command line

ip cef accounting load-balance-hash           "per destination sharing"

  if)#ip load-sharing per-packet                " per packets sharing "

sh ip cef {prefix} internal  

clear ip cef * prefix statistics