Addressing........................................................................................................................ 38
Subnets ............................................................................................................................ 40
Changing the AT-AR240E LAN - USB IP address ........................................................... 42
IP Routing......................................................................................................................... 43
CHAPTER 4 DHCP ..................................................................................................................45
The Dynamic Host Configuration Protocol ....................................................................... 45
The AT-AR240E’s support for DHCP ............................................................................... 46
DHCP Relay ..................................................................................................................... 46
DHCP Server.................................................................................................................... 48
CHAPTER 5 DNS.....................................................................................................................51
DNS introduction .............................................................................................................. 51
DNS Relay........................................................................................................................ 52
DNS Client........................................................................................................................ 53
CHAPTER 6 Security ..............................................................................................................54
Introduction....................................................................................................................... 54
Application Gateway......................................................................................................... 54
Stateful Inspection ............................................................................................................ 55
Firewall ............................................................................................................................. 56
Dynamic Port Opening ..................................................................................................... 56
Attack Detection and Blocking.......................................................................................... 56
NAT .................................................................................................................................. 57
Security interfaces ............................................................................................................ 57
Firewall ............................................................................................................................. 59
Precedence rule for overlapping filters ............................................................................. 64
Configuration example 1 for Firewall ................................................................................ 64
Dynamic Port Opening ..................................................................................................... 66
Configuration example 1 for Dynamic Port Opening ........................................................ 70
Configuration example 2 for Dynamic Port Opening ........................................................ 72
Configuration example 2 for Dynamic Port Opening ........................................................ 73
Attack Detection and Blocking.......................................................................................... 75
NAT ................................................................................................................................. 76
Configuration example 1 for NAT ..................................................................................... 80
Configuration example 2 for NAT ..................................................................................... 82
Configuration example 3 for NAT ..................................................................................... 83
Configuration example 4 for NAT ..................................................................................... 84
Interactions of NAT and other security features. .............................................................. 86
Firewall filters and reserved mappings. ............................................................................ 86
NAT and Dynamic Port Opening ...................................................................................... 86
CHAPTER 7 SNMP..................................................................................................................87
Introduction....................................................................................................................... 87
Simple Network Management Protocol (SNMP)............................................................... 87
Communities and Views ................................................................................................... 87
AT-AR240E Console ........................................................................................................ 88
How to close the console.................................................................................................. 90
HELP on SNMP console commands................................................................................ 91
Command Reference ....................................................................................................... 92
CHAPTER 8 APPENDIX A....................................................................................................... 94
Factors underlying the design of ATM.............................................................................. 94
LAN/WAN/Voice integration.............................................................................................. 95
Cell multiplexing ...............................................................................................................95
Other significant features of ATM ..................................................................................... 96
