Extreme Networks Summit Summit24, Инструкция по установке и эксплуатации

Страница: 171 / 244

Relative Route Priorities
Summit24e3 Switch Installation and User Guide 171
• 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.
• 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.
Proxy ARP Between Subnets
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.
Relative Route Priorities
Table 47 lists the relative priorities assigned to routes depending upon the learned source of the route.
CAUTION
Although these priorities can be changed, do not attempt any manipulation unless you are expertly
familiar with the possible consequences.
Table 47: Relative Route Priorities
Route Origin Priority
Direct 10
BlackHole 50
Static 1100
ICMP 1200
OSPFIntra 2200
OSPFInter 2300
RIP 2400
OSPFExtern1 3200
OSPFExtern2 3300