- Enterasys Security Router User's Guide

Features
XSR User’s Guide 13-5
Figure 13-4 IP over ATM Network Diagram
Restrictions of this implementation are as follows:
• Maximum MTU of 1500 bytes
• NLPID-formatted routed IP version 4 PDUs over ATM PVCs are not supported
• LLC-encapsulated bridge PDUs are not supported. Any bridged PDUs received and PDUs
received which specify a foreign MAC address (not the XSR’s) are silently discarded.
• Dynamic IP addresses acquired by DHCP are not supported
• ATM SVCs are not supported
ADSL Limitations
Consider the following caveats regarding ADSL operations on the XSR:
• The standard ADSL configuration reserves circuit 1/33 (VPI/VCI) as the Vendor Specific
Channel) per ADSL Forum TR-008
•One Virtual Path only is supported
• The maximum overall MTU is 1500 bytes; default is 1492 bytes
• Bridging protocols and operations must be disabled on access concentrators
• ILMI protocols must be disabled on access concentrators
• One ADSL NIM card type is supported per XSR: Annex A or B.
• PPPoE connects to the first advertised service name only
ADSL Hardware
NIM Card
Two versions of the ADSL NIM are available for XSR Series 1800 and 3000 routers:
• Version 1 complies with ITU-T Recommendation G.992.1 Annex A - ADSL over POTS (Part #:
NIM-ADSL-AC-01).
• Version 2 complies with ITU-T Recommendation G.992.1 Annex B - ADSL over ISDN (Part #:
NIM-ADSL-B-01).
PC
PC
PHY
802.3
IP
1483
IP
ATM
ADSL
Access
Concentrator
Router / Modem
DSL
ATM
SONET
ATM
DSLAM
Routed encapsulation
- LLC/SNAP only
IP
Frwd
Caution: The XSR supports one installed ADSL NIM card type at a time (multiple installed cards
must be of the same type).