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Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)
Chapter4 Configuring Interfaces About ATM Uplinks (Catalyst 8540)
SR1 72036 SR2 18806 SR3 0 SR4 0 SR5 0
MT1 15143 MT2 0 MT3 0 MT4 0 MT5 6
MT6 0 MT7 0 MT8 0 MT9 0
ST1 0 ST2 0
MRXS 262160 MTXS 16 SRXS 3 STXS 0
About ATM Uplinks (Catalyst 8540)
ATM uses cell-switching and multiplexing technology that combines the benefits of circuit switching
(constant transmission delay and guaranteed capacity) with those of packet switching (flexibility and
efficiency for intermittent traffic). ATM is a common network technology for enterprise backbones,
MANs, and WANs.By using an ATM uplink, Layer 3 trafficcan be routed over an ATM network. The
ATMuplink facilitates this by segmenting packet data into fixed-size cells at the transmitting end and
reassembling them into packets at the receiving end. This conversion process is defined by the ATM
adaptation layer (AAL).
For further information about ATM and its implementation on the Catalyst 8540 MSR and
Catalyst 8510 MSR, refer to the Guide to ATM Technology.
About the ATM Uplink Interface
The ATMuplink interface allows the Catalyst 8540 switch router to be deployed as part of an existing
network where a router with an ATM interface would otherwise have been utilized. Additionally, the
ATMuplink interface allows a Catalyst 8540 deployed as a Layer 3 switch (CSR) to be connected to a
Catalyst 8540 deployed as an ATM switch (MSR).
Figure 4-6 shows an example application of the ATM uplink in which traffic from a LAN switch is
aggregated at the Catalyst 8540 CSR and then passed to the ATM network over the ATM uplink. The
Layer 3 enabled ATM uplink supports RFC 1483 (Multiprotocol Encapsulation over ATM), which
provides for the mapping of Layer 3 addresses to ATMvirtual circuits, and traffic shaping. Refer to the
Guide to ATM Technology for additional information on RFC 1483.
Figure 4-6 Layer 3 Traffic with ATM Uplink
Wiring closet
4Gb Ethernet
Catalyst 8540 CSR
Catalyst 8540 MSR
ATM uplink
ATM network
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