Technical data

100 Chapter 4. Configuring Special Features
With Reject, an ICMP REJECT (Internet Control Management Protocol) is sent to reject the packet.
IP Filter Commands
The following two commands are used respectively to define IP filters on the Ethernet interface and on the remote
interface. For extensive information on the syntax of these two commands, refer to the
Command Line Interface
Reference
chapter.
eth ip filter
<command> <type> <action> <parameters> [<port#>]
remote ipfilter
<command> <type> <action> <parameters> <remoteName>
Special Notes
IP filters of Input type are checked
before
the IP packet is redirected by ICMP. This could adversely affect local
LANs that use ICMP redirect to dynamically learn IP routes. IP filters of Input type are checked
before
the IP
packet is sent to the router itself as a host.
Example:
The following commands will stop
any
attempt by a host coming from the remote internet from sending an IP
packet to the telnet port. Hence, the router will not see the packet, and the packet will not be forwarded.
remote ipfilter insert input drop -p tcp -dp 23 internet
save
These commands will stop
any
attempt by a host coming from the remote internet from sending an IP packet to
the telnet port “through” the router to a different interface. The router itself could still receive the IP packet, hence
the remote host could Telnet to the router itself.
remote ipfilter insert forward drop -p tcp -dp 23 internet
save
L2TP Tunneling — Virtual Dial-Up
This section has four parts:
•The
Introduction
provides a general overview of L2TP tunneling.
•The
L2TP Concepts
section explains LNS, L2TP client, LAC, dial user, tunnels, and sessions.
•
Configuration
describes preliminary configuration steps and verification steps and lists commands associated
with the configuration of L2TP and PPP sessions.
•The
Sample Configurations
section provides two examples with step-by-step instructions: a simple L2TP
client configuration example and a complete LNS and L2TP client configuration example.
Introduction
L2TP (Layer 2 Tunneling Protocol) is used to forward a PPP link from a remote site to a corporate site across the
Internet, thus creating virtual paths called tunnels. Because tunneling involves encapsulating data, packets can be