Subnet-Directed Broadcast Forwarding; Proxy Arp; Arp-Incapable Devices - Extreme Networks Summit Summit24 Installation And User Manual

IP Unicast Routing
IP Route Sharing
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 multipath
(ECMP) routing. To use IP route sharing, use the following command:
enable iproute sharing
Next, configure static routes and/or OSPF as you would normally. ExtremeWare supports unlimited
route sharing across static routes and up to eight ECMP routes for OSPF.
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.

Subnet-Directed Broadcast Forwarding

You can enable or disable the hardware forwarding of subnet-directed broadcast IP packets. This allows
the switch to forward subnet-directed broadcast packets at wire-speed.
To enable or disable hardware forwarding, use the following command:
[enable | disable] ipforwarding fast-direct-broadcast [vlan <vlan_name>]
The entries are added to the IP forwarding table as standard entries and you can view them using the
command.
show ipfdb
You can also configure the VLAN router interface to either forward and process all subnet-directed
broadcast packets, or to simply forward these packets after they have been added to the IP forwarding
database. The latter option allows you to improve CPU forwarding performance by having upper
layers, such as UDP and TCP, ignore broadcast packet processing (for example, if the packets have
IP-options configured).
To enable or disable broadcast packet processing, use the following command:
[enable | disable] ipforwarding ignore-broadcast vlan <vlan_name>

Proxy 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-Incapable Devices

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:
170 Summit24e3 Switch Installation and User Guide