Paul, did you get this working?  If not, a suggestion or three inline...

On Thu, 10 Jun 2004, Paul Burke wrote:

> Configuring my first Linux under S/390 and cannot get Linux to communicate
> with the network. Following is a brief overview of the environment.
>
> We run a class C network 192.168.168. with a subnet mask of 255.255.255.128.
> Existing network runs on low order, Linux network runs on the high order.
> Connectivity between the network to z/VM on a Multiprise 3000 H30 is
> provided by a Bustech MAN device owned by VM TCP/IP.

I'm not familiar with this guy...  If it's a 'smart' device like an OSA
-- if you can call any OSA smart ;) -- it might need some configuration to
know that there are addresses behind the VM IP stack.  On an OSA we'd be
talking about PRIROUTER or manipulation of the OAT...

> 192.168.168.20 is the VM stack
> 192.168.168.129 is the Linux stack
> 192.168.168.35 is a PC on the network
>
> >From a Z/VM CMS virtual machine I can ping all resources.
> >From Linux, I can ping VM but not the PC.
> >From the PC, I can ping VM but not Linux.

<some snippage>
>
> netstat gate
>
> VM TCP/IP Netstat Level 420
>
> Known gateways:
>
> NetAddress      FirstHop   Flgs PktSz Subnet Mask  Subnet Value  Link
> ----------      --------   ---- ----- -----------  ------------  ------
> 192.168.168.0   <direct>   US   1500  0.0.0.128    0.0.0.0       VMLINK
> 192.168.168.129 <direct>   UHS  1500  HOST                       LINUX1V
> Ready; T=0.02/0.03 10:50:49

You don't appear to have a default gateway in z/VM TCPIP -- not critical
for this, perhaps, as you have specific routes for the networks you need,
but if Linux needs to get to other places (the Internet for example) you
will need to set this up using a DEFAULTNET in your GATEWAY statement.

> Linux (192.168.168.129 - Debian distribution)
>
> route
>
> Kernel IP routing table
> Destination     Gateway        Genmask         Flags Metric Ref Use Iface
> 192.168.168.20  *              255.255.255.255 UH    0      0   0   ctc0
> 192.168.168.129 *              255.255.255.255 UH    0      0   0   ctc0
> 127.0.0.0       *              255.0.0.0       U     0      0   0   lo
> default         192.168.168.20 0.0.0.0         UG    0      0   0   ctc0

This looks okay.

> ping -c 1 192.168.168.129
<snip working>
> ping -c 1 192.168.168.20
<snip working>
> ping -c 1 192.168.168.35
<snip not working>

Definitely somebody's not routing...

> PC (192.168.168.35)
>
> C:\>ipconfig /all
>
> Ethernet adapter Local Area Connection:
>
>         Connection-specific DNS Suffix  . :
>         Description . . . . . . . . . . . : 3Com 3C920 Integrated Fast
> Ethernet
> Controller (3C905C-TX Compatible)
>         Physical Address. . . . . . . . . : 00-06-5B-12-99-19
>         DHCP Enabled. . . . . . . . . . . : No
>         IP Address. . . . . . . . . . . . : 192.168.168.35
>         Subnet Mask . . . . . . . . . . . : 255.255.255.128
>         Default Gateway . . . . . . . . . : 192.168.168.1
>         DNS Servers . . . . . . . . . . . : 154.15.243.2
>                                             154.15.244.2
>         Primary WINS Server . . . . . . . : 192.168.168.3
>
> C:\>route print
> ===========================================================================
> Interface List
> 0x1 ........................... MS TCP Loopback interface
> 0x1000003 ...00 06 5b 12 99 19 ...... 3Com EtherLink PCI
> ===========================================================================
> ===========================================================================
> Active Routes:
> Network Destination        Netmask          Gateway       Interface  Metric
>           0.0.0.0          0.0.0.0    192.168.168.1  192.168.168.35       1
>         127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1       1
>     192.168.168.0  255.255.255.128   192.168.168.35  192.168.168.35       1
>    192.168.168.35  255.255.255.255        127.0.0.1       127.0.0.1       1
>   192.168.168.128  255.255.255.128   192.168.168.20  192.168.168.35       1
>   192.168.168.255  255.255.255.255   192.168.168.35  192.168.168.35       1
>         224.0.0.0        224.0.0.0   192.168.168.35  192.168.168.35       1
>   255.255.255.255  255.255.255.255   192.168.168.35  192.168.168.35       1
> Default Gateway:     192.168.168.1
> ===========================================================================
> Persistent Routes:
>   None

Right.  This lot tells me that the Windows machine is okay too.  You have
the correct subnet mask on the Ethernet, and an appropriate route to
direct the 192.168.168.128 network to the VM IP stack (so, changing the
default router at 192.168.168.1 to add this might help other machines, but
not this one in this case).

Also, Proxy ARP will not assist either, because the Linux guest is not in
the 192.168.168.0/25 network that the Ethernet is configured for (this
network stops at .127 - the broadcast address - and the Linux guest is at
.129).

My suggestions: double-check that there is no firewall product on the PC,
or a firewall configuration on the Linux guest, that is stopping the
traffic flowing.  If that's clear, check that IP forwarding is enabled in
the VM IP stack (ASSORTEDPARMS NOFWD must not appear in PROFILE TCPIP, and
you should see "IP forwarding is enabled" in the TCPIP service machine's
spool output).

Cheers,
Vic Cross

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