User guide

E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
11-5
P
ROXY
ARP
You can also configure blackhole routes — traffic to these destinations is silently
dropped.
IP R
OUTE
S
HARING
IP route sharing allows multiple equal-cost routes to be used concurrently. IP route
sharing can be used with static routes or with OSPF routes. In OSPF, this capability is
referred to as equal cost multi-path (ECMP) routing. To use IP route sharing, use the
following command:
enable route sharing
Next, configure static routes and/or OSPF as you would normally. As many as five
ECMP routes can be used for a given destination.
Route sharing is useful only in instances where you are constrained for bandwidth. This
is typically not the case using Extreme switches. Using route sharing makes router
troubleshooting more difficult because of the complexity in predicting the path over
which the traffic will travel.
P
ROXY
ARP
Proxy Address Resolution Protocol (ARP) was first invented so that ARP-capable
devices could respond to ARP Request packets on behalf of ARP-incapable devices.
Proxy ARP can also be used to achieve router redundancy and simplify IP client
configuration. The switch supports proxy ARP for this type of network configuration.
The section describes some example of how to use proxy ARP with the switch.
ARP-I
NCAPABLE
D
EVICES
To configure the switch to respond to ARP Requests on behalf of devices that are
incapable of doing so, you must configure the IP address and MAC address of the
ARP-incapable device using the use the following command:
config iparp add proxy <ipaddress> {<mask>} <mac_address> {always}
Once configured, the system responds to ARP Requests on behalf of the device as long
as the following conditions are satisfied:
• The valid IP ARP Request is received on a router interface.
• The target IP address matches the IP address configured in the proxy ARP table.