Extreme Networks ExtremeWare XOS 11.3, Manual

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IPv4 Unicast Routing
ExtremeWare XOS 11.3 Concepts Guide
500
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. You can use proxy ARP 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.
Configuring IPv4 Unicast Routing
This section describes the commands associated with configuring IP unicast routing on the switch. To
configure routing:
1 Create and configure two or more VLANs.
2 Assign each VLAN that will be using routing an IP address using the following command:
configure vlan <vlan_name> ipaddress [<ipaddress> {<ipNetmask>} | ipv6-link-local
| {eui64} <ipv6_address_mask>]
Ensure that each VLAN has a unique IP address.
3 Configure a default route using the following command:
configure iproute add default <gateway> {vr <vrname>} {<metric>} {multicast-only |
unicast-only}
Default routes are used when the router has no other dynamic or static route to the requested
destination.
4 Turn on IP routing for one or all VLANs using the following command:
enable ipforwarding {ipv4 | broadcast | ignore-broadcast | fast-direct-broadcast}
{vlan <vlan_name>}
5 Configure the routing protocol, if required. For a simple network using RIP, the default configuration
may be acceptable.
6 Turn on RIP or OSPF using one of the following commands:
enable rip
enable ospf