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10 ssh, Figure 202 remote management: icmp, Table 144 remote management: icmp – ZyXEL Communications P-2602HWLNI User Manual

Page 354

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Chapter 23 Remote Management Configuration

P-2602HWLNI User’s Guide

354

Figure 202 Remote Management: ICMP

The following table describes the labels in this screen.

23.10 SSH

You can use SSH (Secure SHell) to securely access the ZyXEL Device’s command line
interface. Specify which interfaces allow SSH access and from which IP address the access
can come.
Unlike Telnet or FTP, which transmit data in plaintext (clear or unencrypted text), SSH is a
secure communication protocol that combines authentication and data encryption to provide
secure encrypted communication between two hosts over an unsecured network. In the
following figure, computer A on the Internet uses SSH to securely connect to the WAN port of
the ZyXEL Device for a management session.

Table 144 Remote Management: ICMP

LABEL

DESCRIPTION

ICMP

Internet Control Message Protocol is a message control and error-reporting

protocol between a host server and a gateway to the Internet. ICMP uses Internet

Protocol (IP) datagrams, but the messages are processed by the TCP/IP software

and directly apparent to the application user.

Respond to Ping

on

The ZyXEL Device will not respond to any incoming Ping requests when Disable is

selected. Select LAN to reply to incoming LAN Ping requests. Select WAN to reply

to incoming WAN Ping requests. Otherwise select LAN & WAN to reply to both

incoming LAN and WAN Ping requests.

Do not respond to

requests for

unauthorized

services

Select this option to prevent hackers from finding the ZyXEL Device by probing for

unused ports. If you select this option, the ZyXEL Device will not respond to port

request(s) for unused ports, thus leaving the unused ports and the ZyXEL Device

unseen. By default this option is not selected and the ZyXEL Device will reply with

an ICMP Port Unreachable packet for a port probe on its unused UDP ports, and a

TCP Reset packet for a port probe on its unused TCP ports.
Note that the probing packets must first traverse the ZyXEL Device's firewall

mechanism before reaching this anti-probing mechanism. Therefore if the firewall

mechanism blocks a probing packet, the ZyXEL Device reacts based on the

corresponding firewall policy to send a TCP reset packet for a blocked TCP packet

or an ICMP port-unreachable packet for a blocked UDP packets or just drop the

packets without sending a response packet.

Apply

Click Apply to save your customized settings and exit this screen.

Cancel

Click Cancel to begin configuring this screen afresh.