Juniper JUNOSE SOFTWARE 11.2.X - LINK LAYER CONFIGURATION GUIDE 7-7-2010 Configuration Manual page 608

JunosE 11.2.x Link Layer Configuration Guide
ppp chap-challenge-length
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the ppp authentication virtual-router command specifies a nondefault VR, AAA
returns the specified VR.
If the VR specified in a profile with the ip virtual-router command differs from the
VR provided by AAA, IP uses the VR provided by AAA when the dynamic IP upper-layer
interface is created. For more information about using the ip virtual-router command,
see "ip virtual-router" on page 570.
The router supports the MD5 authentication algorithm for CHAP authentication.
Example 1—Specifies PAP or CHAP as the primary authentication protocol, and the
other authentication protocol as the alternative. For example, the following command
specifies pap as the primary authentication protocol and chap as the alternate.
host1(config-if)#ppp authentication pap chap
The router requests the use of PAP as the authentication protocol (because it appears
first in the command line). If the peer refuses to use PAP, the router requests the CHAP
protocol. If the peer refuses to negotiate authentication, the router terminates the PPP
session.
NOTE: The JunosE Software's PPP application accepts null usernames during PAP and
CHAP authentication. When the PPP application receives an authentication request
that includes a null username, PPP passes the request to AAA. To take advantage of
this feature, configure your authentication server to support the use of null usernames.
Example 2—Specifies a virtual router for the authentication virtual router context. This
command is available in static configurations and in profiles.
host1(config-if)#ppp authentication virtual-router boston pap chap
Use the no version to specify that the router does not require authentication.
See ppp authentication.
Use to modify the length of the CHAP challenge by specifying the minimum length and
maximum length.
CAUTION: Do not use the ppp chap-challenge-length command; increasing the
minimum length (from the default 16 bytes) or decreasing the maximum length (from
the default 32 bytes) reduces the security of your router.
Specify the minimum and maximum lengths in bytes in the range 8–63.
The maximum length must be greater than or equal to the minimum length.
Example
host1(config-profile)#ppp chap-challenge-length 24 28
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