MLO PPP notes

The addition of rigel.sdsu.edu to the computers at MLO made a change necessary to the networking between vega.sdsu.edu and alnitak.sdsu.edu. I freely admit that I know that this document describes the wrong way to accomplish this task. Historically, there has been a PPP link between alnitak.sdsu.edu and vega.sdsu.edu. Since I have always been leery of putting alnitak on the internet, vega does not advertise this link (no traffic is routed between vega's interfaces.) This is still the case, but now rigel.sdsu.edu is connected to alnitak's ethernet interface. This required changes to the network configuration of rigel, alnitak, and vega. The basic design was to have the "ethernet" segment at MLO be a 16 node subnet (network 130.191.225.32, netmask 255.255.255.240) so that alnitak could route traffic between it's ppp0 interface and it's le0 interface. With it's default route set to the far end of the ppp0 interface, alnitak serves as a router between these two networks. The only complication was that the far end of the ppp0 link (130.191.225.40) was unfortunately chosen to be an IP that was on the subnet attached to le0. This meant that alnitak had to be configured to arp for this IP for other hosts on the 130.191.225.32 network.

Changes to rigel.sdsu.edu
1. Change rigel's IP address
  IP address changed to 130.191.225.43 in /etc/hosts
2. Change rigel's netmask
  netmask changed to 255.255.255.240 in /etc/netmasks
3. Change rigel's default route
  default route changed to be 130.191.225.41 (alnitak) in /etc/defaultrouter
Changes to alnitak.sdsu.edu
1. Change alnitak's le0 netmask
  alnitak's le0 netmask changed to 255.255.255.240 in /etc/netmasks
2. Change alnitak's default route
  alnitak's default route changed to 130.191.225.40 in /etc/defaultrouter
3. Add a permanent arp entry on alnitak for the far side of the PPP link
  alnitak set to arp for 130.191.225.40 in /etc/rc.local
```
            #
            # publish our ethernet address as the one for 130.191.225.40
            # (far end of PPP line) because of broken way in which we
            # subnet
            #
            /usr/etc/arp -s 130.191.225.40 08:00:20:0b:d7:ed pub
	    
```

Changes to vega.sdsu.edu

Add a static host based route to rigel through alnitak
add a static route to rigel through alnitak in /etc/init.d/ppp

            # add a static route to rigel
            /usr/sbin/route add host 130.191.225.43 130.191.225.41

Snapshot of the three host's network configuration

        rigel:

        # /usr/sbin/ifconfig -a 
        lo0: flags=849 mtu 8232
                inet 127.0.0.1 netmask ff000000 
        hme0: flags=863 mtu 1500
                inet 130.191.225.43 netmask fffffff0 broadcast 130.191.225.47
                ether 8:0:20:b9:6d:a5 
        # netstat -rn

        Routing Table:
          Destination           Gateway           Flags  Ref   Use   Interface
        -------------------- -------------------- ----- ----- ------ ---------
        130.191.225.32       130.191.225.43        U        3    134  hme0
        224.0.0.0            130.191.225.43        U        3      0  hme0
        default              130.191.225.41        UG       0      9  
        127.0.0.1            127.0.0.1             UH       0   8061  lo0
        # 

        alnitak:

        alnitak:/etc [53]# ifconfig -a
        le0: flags=63
                inet 130.191.225.41 netmask fffffff0 broadcast 130.191.225.32
        lo0: flags=49
                inet 127.0.0.1 netmask ff000000 
        ppp0: flags=51
                inet 130.191.225.41 --> 130.191.225.40 netmask ffff0000 
        ppp1: flags=10
        ppp2: flags=10
        ppp3: flags=10
        ppp4: flags=10
        alnitak:/etc [54]# netstat -rn
        Routing tables
        Destination          Gateway              Flags    Refcnt Use        Interface
        130.191.225.40       130.191.225.41       UH       3      3905       ppp0
        127.0.0.1            127.0.0.1            UH       1      46         lo0
        130.191.225.32       130.191.225.41       U        3      2474       le0
        default              130.191.225.40       UG       0      21         ppp0
        alnitak:/etc [55]# arp -a
        mintaka (130.191.225.40) at 8:0:20:b:d7:ed permanent published
        rigel (130.191.225.43) at 8:0:20:b9:6d:a5
        alnitak:/etc [56]# 

        vega:

        # /usr/sbin/ifconfig -a
        lo0: flags=849 mtu 8232
                inet 127.0.0.1 netmask ff000000 
        le0: flags=863 mtu 1500
                inet 130.191.225.1 netmask ffffff00 broadcast 130.191.225.255
                ether 8:0:20:73:5b:c9 
        ppp0: flags=8d1 mtu 1500
                inet 130.191.225.40 --> 130.191.225.41 netmask ffffff00 
        # netstat -rn
        
        Routing Table:
          Destination           Gateway           Flags  Ref   Use   Interface
        -------------------- -------------------- ----- ----- ------ ---------
        130.191.225.41       130.191.225.40        UH       3      4  ppp0
        130.191.225.43       130.191.225.41        UGH      0     11  
        130.191.225.0        130.191.225.1         U        3  12145  le0
        224.0.0.0            130.191.225.1         U        3      0  le0
        default              130.191.225.254       UG       0 159746  
        127.0.0.1            127.0.0.1             UH       01329305  lo0
        #

Bill Morris

Last modified: Thu Mar 1 10:48:51 PST 2001