GGSN p-t-p address?

[Keith]

Hi all, idle curiosity here more than anything.....

I noticed that if I bring up a pppd link with a GSM modem to an osmo
stack GPRS network, I get assigned an IP address from the pool as
configured on osmo-ggsn;

  ip prefix dynamic 10.20.0.0/16
  ip dns 0 192.168.11.2
  ip dns 1 192.168.11.2
  ip ifconfig 10.20.20.253/16

but the p-t-p address is 192.168.100.101;

Sat Aug 18 15:45:38 2018 daemon.notice pppd[21227]: local  IP address
10.20.0.8
Sat Aug 18 15:45:38 2018 daemon.notice pppd[21227]: remote IP address
192.168.100.101

Here's the resulting ifconfig:

3g-gwan   Link encap:Point-to-Point Protocol 

          inet addr:10.20.0.8  P-t-P:192.168.100.101  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:3 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:54 (54.0 B)  TX bytes:76 (76.0 B)

This is not really a problem but I thought it was weird so I looked for
this IP (192.168.100.101) in the source code but it was nowhere to be
found. I'm a bit rusty on ppp, but should it not be the address
configured in the ggsn's ip config?

I thought maybe it was coming from the local pppd stack, so I booted an
old windows 7 machine and connnected the GSM modem, and it got the same
p-t-p address of 192.168.100.101

thnx/

K.