Hello,
Please find the answer to your queries in the above post as below:-
1. set interfaces ge-0/0/3 unit 0 family inet address 1.1.1.2/30 <--in r.s.* this interface is our default gateway?192.168.1.1?
Yes, In R.S. This is your default gateway interface (connected to the modem/ router).
2. set interfaces st0 unit 0 family inet address 10.11.11.10/24<--in r.s. this is our virtual ip?Right?We can set is as we want?
Yes, This is a virtual IP and you can set it as you want or you can even leave this interface without an IP address (unnumbered) but you will have to atleast configure "family inet" for this interface to work. Also you will have to assign this interface to a security zone.
3. set routing-options static route 0.0.0.0/0 next-hop 1.1.1.1<--Which is the role of 1.1.1.1 and what is its logic connection to 1.1.1.2?
This is the default route which should be present on the SRX to send all the traffic from SRX to the next hop. 1.1.1.1 is your next hop IP address ( In R.S. it should be the IP address of the router/modem connecting to the SRX). When you use PPPoE interface, generally the default route is also learned through PPPoE and in such case you will not have to configure the above route but if it is not learned through PPPoE then you have to configure the route as "set routing-options static route 0.0.0.0/0 next-hop pp0.0".
set routing-options static route 192.168.168.0/24 next-hop st0.0 - This route is for specifying the encryption domain of the VPN tunnel. This route will mean that if any traffic on SRX comes to go to the destination 192.168.168.0/24 then it has to go over the tunnel interface st0.0. (192.168.168.0/24 is the remote subnet which should be accessible on the VPN tunnel).
Hence as i have answered the query no. 3 if the default route is already present on SRX learnt through PPPoE then you do not need the route set routing-options static route 0.0.0.0/0 next-hop pp0.0 else you will need it.
Thanks,
Pulkit Bhandari
Please mark my response as Solution Accepted if it Helps, Kudos are Appreciated too. 