I couldn't figure out what's the problem with the PPPoE link. Here is the log entries I have found on pfSense. The interface is up and IP address has been requested, but all packets are said to be lost at 100%.
This is the overview of these two gateways
And the configuration page
And link to the log entries: http://paste.ubuntu.com/10768804/
Apr 7 11:16:35 ppp: [opt1_link0] LCP: auth: peer wants PAP, I want nothing
Apr 7 11:16:35 ppp: [opt1_link0] PAP: using authname "xxxxxxx"
Apr 7 11:16:35 ppp: [opt1_link0] PAP: sending REQUEST #1 len: 24
Apr 7 11:16:35 ppp: [opt1_link0] LCP: LayerUp
Apr 7 11:16:35 ppp: [opt1_link0] PAP: rec'd ACK #1 len: 85
Apr 7 11:16:35 ppp: [opt1_link0] MESG: 0;User(xxxxxxx@bmcc.com) Authenticate OK, Request Accept by chinamobile.com
Apr 7 11:16:35 ppp: [opt1_link0] LCP: authorization successful
Apr 7 11:16:35 ppp: [opt1_link0] Link: Matched action 'bundle "opt1" ""'
Apr 7 11:16:35 ppp: [opt1_link0] Link: Join bundle "opt1"
Apr 7 11:16:35 ppp: [opt1] Bundle: Status update: up 1 link, total bandwidth 64000 bps
Apr 7 11:16:35 ppp: [opt1] IPCP: Open event
Apr 7 11:16:35 ppp: [opt1] IPCP: state change Initial --> Starting
Apr 7 11:16:35 ppp: [opt1] IPCP: LayerStart
Apr 7 11:16:35 ppp: [opt1] IPCP: Up event
Apr 7 11:16:35 ppp: [opt1] IPCP: state change Starting --> Req-Sent
Apr 7 11:16:35 ppp: [opt1] IPCP: SendConfigReq #5
Apr 7 11:16:35 ppp: [opt1] IPADDR 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] COMPPROTO VJCOMP, 16 comp. channels, no comp-cid
Apr 7 11:16:35 ppp: [opt1] PRIDNS 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] SECDNS 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] IPCP: rec'd Configure Request #1 (Req-Sent)
Apr 7 11:16:35 ppp: [opt1] IPADDR 172.31.0.1
Apr 7 11:16:35 ppp: [opt1] 172.31.0.1 is OK
Apr 7 11:16:35 ppp: [opt1] IPCP: SendConfigAck #1
Apr 7 11:16:35 ppp: [opt1] IPADDR 172.31.0.1
Apr 7 11:16:35 ppp: [opt1] IPCP: state change Req-Sent --> Ack-Sent
Apr 7 11:16:35 ppp: [opt1] IPCP: rec'd Configure Reject #5 (Ack-Sent)
Apr 7 11:16:35 ppp: [opt1] COMPPROTO VJCOMP, 16 comp. channels, no comp-cid
Apr 7 11:16:35 ppp: [opt1] IPCP: SendConfigReq #6
Apr 7 11:16:35 ppp: [opt1] IPADDR 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] PRIDNS 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] SECDNS 0.0.0.0
Apr 7 11:16:35 ppp: [opt1] IPCP: rec'd Configure Nak #6 (Ack-Sent)
Apr 7 11:16:35 ppp: [opt1] IPADDR 172.31.111.xx
Apr 7 11:16:35 ppp: [opt1] 172.31.111.xx is OK
Apr 7 11:16:35 ppp: [opt1] PRIDNS 221.130.33.60
Apr 7 11:16:35 ppp: [opt1] SECDNS 221.130.33.52
Apr 7 11:16:35 ppp: [opt1] IPCP: SendConfigReq #7
Apr 7 11:16:35 ppp: [opt1] IPADDR 172.31.111.xx
Apr 7 11:16:35 ppp: [opt1] PRIDNS 221.130.33.60
Apr 7 11:16:35 ppp: [opt1] SECDNS 221.130.33.52
Apr 7 11:16:35 ppp: [opt1] IPCP: rec'd Configure Ack #7 (Ack-Sent)
Apr 7 11:16:35 ppp: [opt1] IPADDR 172.31.111.xx
Apr 7 11:16:35 ppp: [opt1] PRIDNS 221.130.33.60
Apr 7 11:16:35 ppp: [opt1] SECDNS 221.130.33.52
Apr 7 11:16:35 ppp: [opt1] IPCP: state change Ack-Sent --> Opened
Apr 7 11:16:35 ppp: [opt1] IPCP: LayerUp
Apr 7 11:16:35 ppp: [opt1] 172.31.111.xx -> 172.31.0.1
Apr 7 11:16:36 ppp: [opt1] IFACE: Up event