User guide

11-6 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
IP U
NICAST
R
OUTING
• The proxy ARP table entry indicates that the system should always answer this ARP
Request, regardless of the ingress VLAN (the
always
parameter must be applied).
Once all the proxy ARP conditions are met, the switch formulates an ARP Response
using the configured MAC address in the packet.
P
ROXY
ARP B
ETWEEN
S
UBNETS
In some networks, it is desirable to configure the IP host with a wider subnet than the
actual subnet mask of the segment. Proxy ARP can be used so that the router answers
ARP Requests for devices outside of the subnet. As a result, the host communicates as if
all devices are local. In reality, communication with devices outside of the subnet are
proxied by the router.
For example, an IP host is configured with a class B address of 100.101.102.103 and a
mask of 255.255.0.0. The switch is configured with the IP address 100.101.102.1 and a
mask of 255.255.255.0. The switch is also configured with a proxy ARP entry of IP
address 100.101.0.0 and mask 255.255.0.0, without the
always
parameter.
When the IP host tries to communicate with the host at address 100.101.45.67, the IP
hosts communicates as if the two hosts are on the same subnet, and sends out an IP
ARP Request. The switch answers on behalf of the device at address 100.101.45.67,
using its own MAC address. All subsequent data packets from 100.101.102.103 are sent
to the switch, and the switch routes the packets to 100.101.45.67.
R
ELATIVE
R
OUTE
P
RIORITIES
Tab le 11-1 lists the relative priorities assigned to routes depending upon the learned
source of the route.
Although these priorities can be changed, do not attempt any manipulation
unless you are expertly familiar with the possible consequences.
Table 11-1: Relative Route Priorities
Route Origin Priority
Direct 10
BlackHole 50
Static 1100