WAN performance configuration Directory
Task list of Fast
switch configuration
Configure global fast switch enable
Configure fast switch enable on the interface
link layer protocol of fast switch supported by link layer
L2TP function’s influence on fast switch
Influences to other module after enabling fast switch
Fast switch realization will
elevate packet forward speed. Fast switch adopts information flow technology and
uses cache memory to process received packets. When the first data flow packet
is forwarded by search route table, if it is configured fast switch, it is going
to exchange router information in cache memory. When forwarding the succeeding
packets, the packets will pass through cache memory exchange information and
forward the packet directly. This simplifies the process for supporting some
special functions under ordinary forward method. It also improve link layer
buffer mechanism and enhance packet forward efficiency.
After
enabling global fast switch and both forwarding and receiving ports are
configured, fast switch works.
Task list of Fast switch configuration
To configure fast switch requires the implementation of the following tasks:
Configure global fast switch enable
Configure fast switch enable on the interface
Configure
global fast switch enable
First you should configure global fast switch enable under global configuration mode, then you are able to cinfigure fast switch on the interface.
command |
function |
Ip
fast-switch enable |
Open the Global fast switch enable |
Configure
fast switch enable on the interface
Then configure the fast switch
function on the interface needs to perform fast switch under interface
configuration mode.
command |
function |
Ip fast-switch
enable |
Open
the fast switch enable on the interface |
link layer
protocol of fast switch supported by link layer
Ethernet
PPP
HDLC
link layer
protocol of fast switch not supported by link layer
SLIP
X25
FR
SDLC
Protocols like x25,SLIP are applied in low speed DDN line. The limit of
forwarding packets are not the efficiency of router forwarding but the line
bandwidth.
Because X25 does not support fast switch, XOT and X25-TCP related functions closely connected to X25 are not affected by fast switch.
L2TP function’s influence on fast switch
When an interface configuration is packed with PPP, and the PPP is configured with L2TP related command during negotiation, the port fast swich function fails. The reason for failure is that the port does not process IP packets anymore but forward them to remote LNS after receiving Client PPP packets.
Influences to other module after enabling
fast switch
IP Acces List
IPSec(tunnel mode)
NAT
RSVP
Because fast switch realization disable some special function on IP layer
to enhance forward speed, some special functions that deals with IP pakets will
be influenced.
Influenced
functions including the following. If the port is configured with fast switch,
the port corresponding function as follow will be invalid.
IP Acces List IP access list related functions
Because fast switch enhance forward efficiency, the function’s
determination function is masked and it is invalid.
Note:
notice that access list invalid means when a port is configured with fast
switch, the port IP packet access list function fails. Other ports that are not
configured with fast switch functions still works.
IPSec(tunnel mode)
When realizing IPSec function, the IP packets need to be
encrypted/decrypted. When processing IPSec packet head, outer IP packet head are
also added/deleted. Because the function occupies much CPU resource, fast switch
will mask this function and makes it invalid.
NAT
While
realizing NAT functions, it requests analysis for IP packet TCP or UDP types,
and port number analysis. The function is maily applied to stub network router.
After configuring fast switch, it is believed that the router is mainly
functioned for forwarding packets instead of the access function in the user
side, so the forward functions which affect the efficiency so much will be
masked.
Similar
to access list, NAT outside address transformation and inside address
transformation are invalid after configured fast switch. The NAT related
functions are still working.
RSVP
After
configured fast switch, it will try its best to forward the packets
without considering saving the resource.