[j-nsp] ipip and gre interfaces

[Blaz Zupan]

I have two upstream STM-1's to two different upstream ISP's connected to two
M5's located in different POPs and two local E3's connecting the M5's. I'd
like to somehow backup the E3's in case they fail (they are going through the
same telco). I thought I'd build a tunnel between the two STM-1's in case the
E3 fails. I don't have a tunnel PIC in any of my M5's and don't want to get on
just to build this tunnel (it would probably be cheaper to move one of the
E3's to another telco and get redundancy this way, which is what I'll
probably eventually do).

What is the usefulness of the ipip and gre interfaces (not the gr-x/x/x and
ip-x/x/x interfaces you get when you have a tunnel PIC)? I successfuly built a
tunnel between the M5's with the ipip interface and can ping the other side
through the tunnel, but trying to route through the tunnel I get a network
unreachable for every packet. Configuration was something like

interfaces {
  ipip {
    unit 0 {
      tunnel {
        source 192.168.1.1;
        destination 192.168.2.1;
      }
      family inet {
        address x.x.x.x/30;
      }
    }
  }
}

... and the opposite on the other side.

Is the usage of those ipip and gre interfaces documented anywhere? I wasn't
able to find any documentation on them.

Any help will be appreciated.