Atm Arp Servers; Forwarding To Nodes Within A Lis - 3Com CoreBuilder 2500 User Manual

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HAPTER OUTING WITH

ATM ARP Servers

IP T
ECHNOLOGY
An ATM ARP server maintains a table of IP addresses and their
corresponding ATM addresses and circuit information. To forward IP
packets over an ATM interface, the network node learns the ATM address
for the corresponding IP address from the ATM ARP server.
Each ATM ARP server supports a single LIS. You can associate two or
more LISs with the same ATM network, but each LIS operates
independently of other LISs on the network.
Several types of network nodes can function as ATM ARP servers:
Any CoreBuilder system with revision 8.1.0 or later of Extended
Switching software
An ATM switch
A UNIX workstation
The following sequence describes how the ATM ARP server learns and
stores information about the IP and ATM addresses of nodes in the
network:
1 A node establishes a connection to the ATM ARP server.
2 The ATM ARP server sends an inverse ATM ARP request to the node,
requesting its IP and ATM address.
3 When the node returns this information, the ATM ARP server stores, or
caches, it in the ATM ARP server table.

Forwarding to Nodes Within a LIS

Nodes can forward packets directly to other nodes in the same LIS. To
forward a packet within the same LIS, the sending node requests a
translation from the destination IP address to the corresponding ATM
address from the ATM ARP server.
If the address is known to the server, the server returns a message
with this address
If the address is not known to the server, the server returns a message
to advise the sending node that the packet is discarded.
When the server returns a destination address, the sending node uses
this learned address to create a virtual circuit (VC) and to forward this
and all subsequent packets to the destination address. The sending
node adds this VC to its ATM ARP cache.