LCP Echo request

We are using the Q2438 (the model I am testing with is the Q2438F) as an add-on board to our embedded Linux device. I am attempting to use the lcp-echo-failure and lcp-echo-interval options on the Linux PPP daemon to monitor the health of the PPP connection. What I am finding is that as soon as the Q2438F allocates the IP address it stops responding to the LCP echo requests.

In the example below, the options are

lcp-echo-failure 10
lcp-echo-interval 3

If I remove the lcp-echo-failure and lcp-echo-interval options, the connection stays up and functional for long periods of time. Also, the lcp-echo-failure/lcp-echo-interval options work fine with the Wavecom Q24EX001 module that we also use with our embedded Linux device: i.e. we continue to get an lcp echo response after the PPP session is established and IP addresses are allocated.

My impression is that this is a bug in the Q2438 PPP implementation. Has anyone had a similar experience?

PPPD output:

sending AT
waiting for response
OKwaiting for connect
Serial connection established.
using channel 7

Using interface ppp98
Connect: ppp98 <--> /dev/ttyCPM4
rcvd [LCP ConfReq id=0x1f <mru 1500> <asyncmap 0x0> <magic 0xf0aa8636> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xa21a43f2> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1f <mru 1500> <asyncmap 0x0> <magic 0xf0aa8636> <pcomp> <accomp>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xa21a43f2> <pcomp> <accomp>]
sent [LCP EchoReq id=0x0 magic=0xa21a43f2]
sent [IPCP ConfReq id=0x1 <addr> <compress VJ 0f 01>]
sent [CCP ConfReq id=0x1 <deflate 15> <deflate(old#) 15> <bsd v1 15>]
rcvd [LCP DiscReq id=0x20 magic=0xf0aa8636]
rcvd [IPCP ConfReq id=0x21 <addr>]
sent [IPCP ConfAck id=0x21 <addr>]
rcvd [LCP EchoRep id=0x0 magic=0xf0aa8636 a2 1a 43 f2]
rcvd [IPCP ConfRej id=0x1 <compress VJ 0f 01>]
sent [IPCP ConfReq id=0x2 <addr>]
rcvd [LCP ProtRej id=0x22 80 fd 01 01 00 0f 1a 04 78 00 18 04 78 00 15 03 2f]
rcvd [IPCP ConfNak id=0x2 <addr> <ms-dns1> <ms-dns3>]
sent [IPCP ConfReq id=0x3 <addr>]
rcvd [IPCP ConfNak id=0x3 <ms-dns1> <ms-dns3>]
sent [IPCP ConfReq id=0x4 <addr>]
rcvd [IPCP ConfNak id=0x4 <ms-dns1> <ms-dns3>]
sent [IPCP ConfReq id=0x5 <addr>]
rcvd [IPCP ConfAck id=0x5 <addr>]
local  IP address
remote IP address
sent [LCP EchoReq id=0x1 magic=0xa21a43f2]
sent [LCP EchoReq id=0x2 magic=0xa21a43f2]
sent [LCP EchoReq id=0x3 magic=0xa21a43f2]
sent [LCP EchoReq id=0x4 magic=0xa21a43f2]
sent [LCP EchoReq id=0x5 magic=0xa21a43f2]
sent [LCP EchoReq id=0x6 magic=0xa21a43f2]
sent [LCP EchoReq id=0x7 magic=0xa21a43f2]
sent [LCP EchoReq id=0x8 magic=0xa21a43f2]
sent [LCP EchoReq id=0x9 magic=0xa21a43f2]
sent [LCP EchoReq id=0xa magic=0xa21a43f2]
No response to 10 echo-requests
Serial link appears to be disconnected.
sent [LCP TermReq id=0x2 "Peer not responding"]
rcvd [LCP TermAck id=0x2]
Connection terminated.
Connect time 0.6 minutes.
Sent 1881 bytes, received 1884 bytes.