Patton electronic Model 2604 manual Block Icmp redirects boxBLockIcmpRedirects

9 • ICMP T1/E1 DACS Administrators’ Reference Guide

Introduction

When networking problems or undesirable conditions occur, the ICMP protocol is used for communicating control or error information plus testing. The statistics listed on the DACS ICMP window (see figure 19) com- prise those contained in RFC 792—Internet Control Message Protocol (ICMP). Implementation of the ICMP group is mandatory for all TCP/IP networks. RFC 1312—ICMP Group of MIB-II Variables—provides the definitions of these variables. It is important to remember that any RFC can be superseded by a newer.

Figure 19. ICMP window

Click on ICMP under the Configuration Menu to monitor DACS ICMP statistics.

Block ICMP redirects (boxBLockIcmpRedirects)

The two options for “Block ICMP Redirects” either allow the reception of ICMP Redirect messages [allowre- directs(0)] or block the reception of ICMP Redirect messages [stopredirects(1)]. The recommended configura- tion is to block the ICMP redirect messages because in some instances they could alter the routing table with undesirable effects, which is considered a breach of security.

ICMP Receive/Send Messages window

The ICMP window displays the ICMP message counters. ICMP messages are displayed in the window as col- umns comprising two types of messages:

•Messages received by the DACS (InMibVariable)

•Messages sent by the DACS (OutMibVariable)

The numbers following the parameters can be a good source of what is happening on the network to point out potential problems. Both gateways (routers) and hosts can send ICMP messages.

Total Received (icmpInMsgs)

The total number of ICMP messages which the 2604 DACS has received. Note that this counter includes all those counted by icmpInErrors (see “w/Errors (icmpInErrors, icmpOutErrors)” on page 57).

56 Introduction