Installing and Administering PPP

138 Chapter 6
Troubleshooting pppd
Solution: Some routers implement a security feature that causes them to not
believe the second IP address that is claimed to be associated with a
particular Ethernet address. If your remote workstation can exchange
packets with all the hosts on your LAN but not with any that are
reachable only through a particular router, then that router is probably
skeptical of your ARP entry. This router security feature is usually
configurable. If it is not configurable, you must put the remote
workstations on their own subnet as described in “Separate Network” in
the section “Connecting a Host to a LAN,” and configure the router so
that it knows that your office hub is the gateway to that subnet.
Scenario: PPP will not connect and the log file shows ’IPCP: Received bad
Configure-Reject.’
Solution: Restart pppd with the novjcomp option. If this fixes the problem, then
the peer may be using a buggy IPCP option negotiation algorithm. Try
running pppd with the rfc1172-vj or the rfc1172-typo-vj option. If these
options do not work, go back to novjcomp and complain to the vendor of
the peer’s implementation of PPP.
Scenario: PPP will not come up, and the peer complains that it has received a
request for IPCP configuration option 3.
Solution: Restart pppd with the rfc1171-addresses option, and report a bug to the
vendor of the peer’s implementation of PPP. If the peer does not
recognize IPCP configuration option 3, it should respond with an IPCP
Configure-Reject rather than exiting altogether.
Scenario: The PPP link comes up and carries IP traffic, but a minute later the log
file shows ’LQM: LQRs: 0/5,’ then ’LQM: Too many Link-Quality-Reports
lost,’ then pppd closes the connection.
Solution: Restart pppd with either the echolqm or the nolqm option and report a
bug to the vendor of the peer’s implementation of PPP.
If the peer does not support Link Quality Monitoring, it should issue a
Configure-Reject during LCP negotiations. If, even after sending an LCP
Configure-Ack in response to HP-UX’s PPP LCP Configure-Request
containing LQM, the peer does not recognize a Link Quality Report, it
should respond with a Protocol-Reject rather than not responding at all.
When pppd sees the Protocol-Reject, it will fall back to using LCP
Echo-Requests for its link status monitoring functions.