IP redirect ?

Hi all !

Who can please give me simple explanations about IP ICMP REDIRECT ? How
does it work ?

I don't understand this explanation on Cisco website :

"Usage Guidelines
An ICMP redirect message can be generated by a router when a packet is
received and transmitted on the same interface. In this situation, the
router will forward the original packet and send a ICMP redirect
message back to the sender of the original packet. This behavior allows
the sender to bypass the router and forward future packets directly to
the destination (or a router closer to the destination).
There are two types of ICMP redirect messages: redirect for a host
address or redirect for an entire subnet.
The ip icmp redirect command determines the type of ICMP redirects sent
by the system and is configured on a per system basis. Some hosts do
not understand ICMP subnet redirects and need the router to send out
ICMP host redirects. Use the ip icmp redirect host command to have the
router send out ICMP host redirects. Use the ip icmp redirect subnet
command to set the value back to the default, which is to send subnet
redirects.
To prevent the router from sending ICMP redirects, use the no ip
redirects interface configuration command"



Thanks !!!

LLFF

ICMP redirects attempt to get a host system (as an example) to send its
packets to the "best" gateway (read router) to get to a particular
destination.

If a host sned a packet to router A and router A has to send it to
router B that is on the same segment, then router A "knows" that the
host is not sending its packet to the best gateway and it send a ICMP
redirect to the host as a hint that it really should be using router B
instead.

http://www.cisco.com/en/US/tech/tk36...80094702.shtml
LLFF wrote:
> Hi all !
>
> Who can please give me simple explanations about IP ICMP REDIRECT ? How
> does it work ?
>
> I don't understand this explanation on Cisco website :
>
> "Usage Guidelines
> An ICMP redirect message can be generated by a router when a packet is
> received and transmitted on the same interface. In this situation, the
> router will forward the original packet and send a ICMP redirect
> message back to the sender of the original packet. This behavior allows
> the sender to bypass the router and forward future packets directly to
> the destination (or a router closer to the destination).
> There are two types of ICMP redirect messages: redirect for a host
> address or redirect for an entire subnet.
> The ip icmp redirect command determines the type of ICMP redirects sent
> by the system and is configured on a per system basis. Some hosts do
> not understand ICMP subnet redirects and need the router to send out
> ICMP host redirects. Use the ip icmp redirect host command to have the
> router send out ICMP host redirects. Use the ip icmp redirect subnet
> command to set the value back to the default, which is to send subnet
> redirects.
> To prevent the router from sending ICMP redirects, use the no ip
> redirects interface configuration command"
>
>
>
> Thanks !!!

Thanks !!!!