Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010 Configuration Manual page 348

JUNOSe 11.1.x Link Layer Configuration Guide
ppp chap-challenge-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.
ppp max-bad-auth
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Configuring Static MLPPP
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.
Example 2 Specify 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 allowable
minimum length and maximum length.
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-if)#ppp chap-challenge-length 24 28
Use the no version to restore the default minimum (16 bytes) and default
maximum (32 bytes).
See ppp chap-challenge-length.
Use to specify the maximum number of authentication retries the router allows
before terminating a PPP session
This value applies to PAP and CHAP authentication.
The range is 0–7. The default is 0, which indicates that no retries are allowed.
Example
host1(config-if)#ppp max-bad-auth 3
Use the no version to return the number of retries to the default, 0.
See ppp max-bad-auth.