3Com 4007, Implementation Manual, Page: 379 / 684

ICMP Redirect
379
Use the Administration Console or the Web Management software to
enable ICMP Redirect.
Important
Considerations
Keep the following things in mind with ICMP Redirect:
■
ICMP Redirect determines if the sending interface is the same as the
receiving interface.
■
ICMP Redirect determines if the source device of the frame is on a
direct-connect network.
■
You can enable or disable ICMP Redirect on a per-interface basis.
■
There is a performance cost associated with this redirect activity. You
have to monitor the activity to gauge its effect on the network.
■
Performance can be affected if the sending device ignores the
recommendations of ICMP Redirect, in which case the performance
cost of ICMP Redirect is incurred while the benefits are wasted.
■
If you disable ICMP Redirect, the hardware routes the frame, and no
messages are sent back to the sending device. At some point,
however, the number of retries associated with less intelligent
hardware routing overtake any benefits that are associated with the
speedier routing that hardware provides.
■
To maximize the effectiveness of ICMP Redirect, have ICMP Redirect
on the module that is connected to the greatest number of other
routing devices.
■
Disable ICMP Redirect if you have overlapped IP interfaces on ports
that are not configured to use 802.1Q VLAN tagging. Doing so
provides better routing performance between the overlapped subnets.
■
If you have two interfaces that belong to different VLANs that share a
given port and you want to completely disable ICMP redirects for that
port, disable the redirects for
each interface that shares that port. If
you disable ICMP Redirect for only one interface and enable it for the
other, you may not get the performance improvement that you want.