BinTec X3200, Руководство пользователя

Страница: 309 / 419

X3200 User’s Guide 309
Special Features
7
7.4 Special Features
7.4.1 Startup Procedure
X3200 does not start its routing activities until the complete configuration is
loaded, especially the defined filters. This means it is not possible to provoke a
system start to make use of an intermediate system state in which perhaps rout-
ing takes place before the filters are active.
7.4.2 Auto Logout
Connections to X3200 via telnet,
➤➤
ISDN Login or serial interface are dis-
connected automatically if no entry is made on the keyboard for a period of 15
minutes. This makes it difficult to read out or change the system configuration
on "forgotten" connections. You can change the time with the command
t <time in seconds>
(see chapter 11.1, page 350 ).
7.4.3 Prevention of Denial-of-Service Attacks
A Denial-of-Service (DoS) attack is an attempt to flood a system or force a re-
start by sending certain packets. This means the system or a certain service can
no longer be used.
Some Denial-of-Service attacks on the router itself are already prevented by the
internal coding.
For example, all X3200 interfaces for which you activate Network Address
Translation (NAT) protect the connected PCs against some DoS attacks with
fragmented packets. The packet fragments are assembled again on passing
through NAT, before the packet can pass the router.
You can prevent some DoS attacks that operate with fake source IP addresses
by using the Back Route Verification function (see chapter 7.2.10, page 302 ).