Dear list readers, I am stuck with the following problem and I hope you can give me some hints or advice. It looks to me like a configuration or routing error. I have an Olimex NB-IoT-DevKit with a Quectel BC66 LTE-NB1 chip which is connected to a RaspberryPI 3B+ via UART connection. I try to make a connection via PPP protocol to the ISP, but that is only “half” working. The LTE modem can dial to the ISP and gets a connection. Both sides exchange LCP configuration messages and IPCP configuration messages. I receive the private static IP address assigned to the SIM card and I also retrieve an IP address for the remote side. The ppp0 interface comes up and is configured with the private static IP address and the P-t-P’s address. My problem is, that I cannot reach anything via that connection. I cannot ping the P-t-P, I cannot ping other addresses. The ISP’s support confirmed that PPP was a viable option to connect and they told me to try the SIM card in a smartphone and to ping 8.8.8.8, so I put the SIM card in an old Android tablet with a SIM card slot and it connected to the remote and I could ping 8.8.8.8 successfully. The only surprising thing I noticed was the fact that the ifconfig command for the dial-up interface on the Android tablet didn’t have a P-t-P remote peer. Apparently the LTE modem is working and the SIM seems to work, too. So I am afraid that I did something wrong with the PPPD configuration. I used pppd version 2.4.7 and the latest version from git’s master branch (5191399f5266bb595f03f5c4fee13153092e2baf). The problem is the same with both versions. Output from pppd (git version): /root/sandbox/pppd/sbin/pppd call quectel-ppp root@raspberrypi:/etc/ppp/peers# /root/sandbox/pppd/sbin/pppd call quectel-ppp pppd options in effect: debug # (from /etc/ppp/peers/quectel-ppp) nodetach # (from /etc/ppp/peers/quectel-ppp) ktune # (from /etc/ppp/peers/quectel-ppp) dump # (from /etc/ppp/peers/quectel-ppp) noauth # (from /etc/ppp/peers/quectel-ppp) refuse-chap # (from /etc/ppp/peers/quectel-ppp) refuse-mschap # (from /etc/ppp/peers/quectel-ppp) refuse-mschap-v2 # (from /etc/ppp/peers/quectel-ppp) refuse-eap # (from /etc/ppp/peers/quectel-ppp) user * # (from /etc/ppp/peers/quectel-ppp) password ?????? # (from /etc/ppp/peers/quectel-ppp) remotename 3gppp # (from /etc/ppp/peers/quectel-ppp) /dev/ttyS0 # (from /etc/ppp/peers/quectel-ppp) 115200 # (from /etc/ppp/peers/quectel-ppp) lock # (from /etc/ppp/peers/quectel-ppp) connect /root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-chat-connect # (from /etc/ppp/peers/quectel-ppp) disconnect /root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-chat-disconnect # (from /etc/ppp/peers/quectel-ppp) record /tmp/quectel.record # (from /etc/ppp/peers/quectel-ppp) nocdtrcts # (from /etc/ppp/peers/quectel-ppp) local # (from /etc/ppp/peers/quectel-ppp) noaccomp # (from /etc/ppp/peers/quectel-ppp) nopcomp # (from /etc/ppp/peers/quectel-ppp) passive # (from /etc/ppp/peers/quectel-ppp) hide-password # (from /etc/ppp/peers/quectel-ppp) novj # (from /etc/ppp/peers/quectel-ppp) novjccomp # (from /etc/ppp/peers/quectel-ppp) ipcp-accept-local # (from /etc/ppp/peers/quectel-ppp) ipcp-accept-remote # (from /etc/ppp/peers/quectel-ppp) ipparam 3gppp # (from /etc/ppp/peers/quectel-ppp) noipdefault # (from /etc/ppp/peers/quectel-ppp) nodefaultroute # (from /etc/ppp/peers/quectel-ppp) noremoteip # (from /etc/ppp/peers/quectel-ppp) noipv6 # (from /etc/ppp/peers/quectel-ppp) noccp # (from /etc/ppp/peers/quectel-ppp) nobsdcomp # (from /etc/ppp/peers/quectel-ppp) nopredictor1 # (from /etc/ppp/peers/quectel-ppp) abort on (BUSY) abort on (NO CARRIER) abort on (NO DIALTONE) abort on (ERROR) abort on (NO ANSWER) timeout set to 120 seconds send (AT^M) expect (OK) AT^M^M OK -- got it send (ATE0^M) expect (OK) ^M ATE0^M^M OK -- got it send (ATI^M) expect (OK) ^M ^M Quectel_Ltd^M Quectel_BC66^M Revision: BC66NBR01A10^M ^M OK -- got it send (AT+CSQ^M) expect (OK) ^M ^M +CSQ: 8,0^M ^M OK -- got it send (AT+CPIN?^M) expect (OK) ^M ^M +CPIN: READY^M ^M OK -- got it send (AT+COPS?^M) expect (OK) ^M ^M +COPS: 0,2,"26201",9^M ^M OK -- got it send (AT+CGREG?^M) expect (OK) ^M ^M +CGREG: 0,5^M ^M OK -- got it send (ATZ^M) expect (OK) ^M ^M OK -- got it send (AT+CGDCONT=1,"IP","iot.1nce.net",,0,0^M) expect (OK) ^M AT+CGDCONT=1,"IP","iot.1nce.net",,0,0^M^M OK -- got it send (ATDT*99#^M) expect (CONNECT) ^M ATDT*99#^M^M CONNECT -- got it Script /root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-chat-connect finished (pid 671), status = 0x0 Serial connection established. using channel 2 Using interface ppp0 Connect: ppp0 <--> /dev/pts/3 sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xd514deb5>] rcvd [LCP ConfReq id=0x1 <mru 1600> <magic 0x85704a90> <asyncmap 0x0> <pcomp> <accomp>] sent [LCP ConfRej id=0x1 <pcomp> <accomp>] rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xd514deb5>] rcvd [LCP ConfReq id=0x2 <mru 1600> <magic 0x85704a90> <asyncmap 0x0>] sent [LCP ConfAck id=0x2 <mru 1600> <magic 0x85704a90> <asyncmap 0x0>] sent [IPCP ConfReq id=0x1 <addr 0.0.0.0>] rcvd [IPCP ConfNak id=0x1 <addr 10.43.124.1>] sent [IPCP ConfReq id=0x2 <addr 10.43.124.1>] rcvd [IPCP ConfReq id=0x1 <addr 10.0.0.1>] sent [IPCP ConfAck id=0x1 <addr 10.0.0.1>] rcvd [IPCP ConfAck id=0x2 <addr 10.43.124.1>] local IP address 10.43.124.1 remote IP address 10.0.0.1 Script /etc/ppp/ip-up started (pid 677) Script /etc/ppp/ip-up finished (pid 677), status = 0x0 Terminating on signal 2 Connect time 14.3 minutes. Sent 3152 bytes, received 0 bytes. Script /etc/ppp/ip-down started (pid 710) sent [LCP TermReq id=0x2 "User request"] Script /etc/ppp/ip-down finished (pid 710), status = 0x0 sent [LCP TermReq id=0x3 "User request"] Connection terminated. abort on (ERROR) abort on (NO DIALTONE) \send (+++ATH^M) Good bye Script /root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-chat-disconnect finished (pid 731), status = 0x0 Serial link disconnected. Modem hangup Waiting for 1 child processes... script pppd (charshunt), pid 670 Child process pppd (charshunt) (pid 670) terminated with signal 15 Peer file /etc/ppp/peers/quectel-ppp: #/etc/ppp/peers/quectel-ppp # Usage:root>pppd call quectel-ppp # Hide password in debug messages hide-password # The phone is not required to authenticate noauth # The chat script connect '/root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-chat- connect' # The close script disconnect '/root/sandbox/pppd/sbin/chat -E -s -v -f /etc/chatscripts/quectel-ch at-disconnect' # Debug info from pppd debug # Serial Device to which the HSPDA phone is connected # Modem path, like /dev/ttyUSB3,/dev/ttyACM0, it depends on your module. # Exmaple given is with the modem mounted at /dev/ttyUSB3 /dev/ttyS0 # Serial port line speed 115200 # If you want to use the HSDPA link as your gateway nodefaultroute # pppd must not propose any IP address to the peer noipdefault # No ppp compression novj novjccomp noccp nobsdcomp noaccomp ktune #nomppe #nomppe-40 #nomppe-128 #nompshortseq #nomultilink nopcomp nopredictor1 noremoteip ipcp-accept-local ipcp-accept-remote refuse-chap refuse-mschap refuse-mschap-v2 refuse-eap local nocrtscts nocdtrcts # For sanity, keep a lock on the serial line lock dump # Keep pppd attached to the terminal # Comment this to get daemon mode pppd nodetach # Network access credenatials. # Set LTE_USERNAME and LTE_PASSWORD before executing pppd -C call # Check with service provider for required details user * password * remotename 3gppp ipparam 3gppp record /tmp/quectel.record passive noipv6 File /etc/chatscripts/quectel-chat-connect ABORT "BUSY" ABORT "NO CARRIER" ABORT "NO DIALTONE" ABORT "ERROR" ABORT "NO ANSWER" TIMEOUT 120 "" AT OK ATE0 OK ATI OK AT+CSQ OK AT+CPIN? OK AT+COPS? OK AT+CGREG? OK ATZ # Connection to the network # Set LTE_APN variable before executing chat -E ... # Check with service provider for required details OK AT+CGDCONT=1,"IP","iot.1nce.net",,0,0 # Dial the number OK ATDT*99# CONNECT File /etc/chatscripts/quectel-chat-disconnect: ABORT "ERROR" ABORT "NO DIALTONE" SAY "\NSending break to the modem\n" "" +++ATH SAY "\nGood bye\n" Some information about the linux system: cat /proc/version Linux version 5.10.11-v7+ (dom@buildbot) (arm-linux-gnueabihf-gcc-8 (Ubuntu/Linaro 8.4.0-3ubuntu1) 8.4.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #1399 SMP Thu Jan 28 12:06:05 GMT 2021 cat /etc/os-release PRETTY_NAME="Raspbian GNU/Linux 10 (buster)" NAME="Raspbian GNU/Linux" VERSION_ID="10" VERSION="10 (buster)" VERSION_CODENAME=buster ID=raspbian ID_LIKE=debian HOME_URL="http://www.raspbian.org/"; SUPPORT_URL="http://www.raspbian.org/RaspbianForums"; BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"; I manually removed the ethernet default route and added a new default route to the ppp0 device: root@raspberrypi:~# route del default root@raspberrypi:~# route add default ppp0 root@raspberrypi:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 ppp0 10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 192.168.2.0 0.0.0.0 255.255.255.0 U 202 0 0 eth0 Output from ifconfig ppp0: root@raspberrypi:~# ifconfig ppp0 ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 10.43.124.1 netmask 255.255.255.255 destination 10.0.0.1 ppp txqueuelen 3 (Point-to-Point Protocol) RX packets 3 bytes 30 (30.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 3 bytes 30 (30.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 If you need more information I am eager to provide those. Do you have any suggestions how to be able to receive the hosts on the "other" side? Best regards, Björn
