Avaya Configuring ATM Services Instrukcja Użytkownika Strona 57

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Understanding ATM, MPOA, and ATM Router Redundancy Concepts
117374-B Rev. 00
1-31
ATM Address Resolution
An address resolution protocol defines a mechanism that enables an IP router to
use the IP address of a network device to learn the physical address of that device.
An Ethernet LAN uses ARP as its address resolution scheme. A LIS uses an
address resolution scheme called ATMARP as defined by RFC 1577.
On a LAN, defined as a broadcast medium, a router obtains the physical address
of a network device by broadcasting an ARP request. In a LIS, which uses a
nonbroadcast ATM medium, a router sends an ATMARP request to an ATMARP
server.
Each IP interface on the LIS opens a VC to the ATMARP server and registers its
IP address and ATM address (Figure 1-12
). Using this information, the server
builds and maintains a table that maps LIS IP addresses to ATM addresses.
A router that needs the ATM address of a host on the LIS sends an ATMARP
request to the server. When the server returns a response containing the address,
the router extracts the ATM address of the host from the response and opens an
SVC directly to the host using ATM UNI signaling.
If the server does not have an entry for the requested IP address, it returns a
negative acknowledgment, signifying that the destination is unreachable.
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