Routed network can't reach outside network

[Ken D'Ambrosio]

On 2020-07-20 05:32, Daniel P. Berrange wrote:
> On Sun, Jul 19, 2020 at 11:54:06AM +0100, Rui Correia wrote:
>> Greetings folks.
>> I've setup libvirtd on my manjaro linux laptop.
>> Got a couple of VM's running (Win10 and Debian10) through NAT without 
>> any
>> issues.
>> 
>> This is what the current network diagram looks like and it works fine:
>> 
>>                            +-----------------------------------+
>>                            |           +---------------------+ |
>>                            |           |     +----------+    | |
>>                            |           |     |Win 10 VM |    | |
>>                            |           |     |10.1.1.10 |    | |
>>                            |           |     +----------+    | |
>>                            | Laptop    |                     | |
>>                            | Manjaro   |     +-------------+ | |
>>                            | 10.0.0.10 |     |Debian 10 VM | | |
>>                  +-------->+           |     |10.1.1.11    | | |
>>                  |         |           |     +-------------+ | |
>>                  |         |           |NAT                  | |
>>                  |         |           |10.1.1.0/24          | |
>>                  |         |           +---------------------+ |
>> +------------+   |         +-----------------------------------+
>> |router      |   |
>> |switch      +---+
>> |10.0.0.0/24 |   |         +---------+
>> +------------+   |         |Desktop  |
>>                  +-------->+Manjaro  |
>>                            |10.0.0.11|
>>                            +---------+
>> 
>> But now I need the debian machine to be accessible from another host 
>> on the
>> lan 10.0.0.0/24 which of course is outside the host.
>> That network diagram would look like this:
>> 
>>                            +-----------------------------------------+
>>                            |              +------------------+       |
>>                            |              |     +----------+ |       |
>>                            |              |     |Win 10 VM | |       |
>>                            |              |     |10.1.1.10 | |       |
>>                            |              | NAT +----------+ |       |
>>                            |              | 10.1.1.0/24      |       |
>>                            |              +------------------+       |
>>                            |  Laptop                                 |
>>                  +-------->+  Manjaro     +------------------------+ |
>>                  |         |  10.0.0.10   |        +-------------+ | |
>>                  |         |              |        |Debian 10 VM | | |
>>                  |         |              |        |10.2.2.10    | | |
>>                  |         |              | Routed +-------------+ | |
>> +------------+   |         |              | 10.2.2.0/24            | |
>> |router      |   |         |              +------------------------+ |
>> |switch      +---+         +-----------------------------------------+
>> |10.0.0.0/24 |   |
>> +------------+   |
>>                  |
>>                  |         +---------+
>>                  |         |Desktop  |
>>                  +-------->+Manjaro  |
>>                            |10.0.0.11|
>>                            +---------+
>> 
>> 
>> So, I've setup a 'routed network' for the Debian 10 VM but it's not 
>> working
>> as I would expect.
>> The host can ping the Debian VM and the Debian VM can ping the host 
>> but the
>> Debian VM cannot ping the router 10.0.0.1 or any ip address on the 
>> internet.
>> I've been using Virtual Machine Manager to set everything up.
>> And this is how the routed network is configured
>> <network connections="1">
>>   <name>routed</name>
>>   <uuid>970a25f7-29b6-4a6b-b890-f593eae4fc15</uuid>
>>   <forward dev="wlo1" mode="route">
>>     <interface dev="wlo1"/>
>>   </forward>
>>   <bridge name="virbr2" stp="on" delay="0"/>
>>   <mac address="52:54:00:bf:35:42"/>
>>   <domain name="routed"/>
>>   <ip address="10.2.2.1" netmask="255.255.255.0">
>>     <dhcp>
>>       <range start="10.2.2.2" end="10.2.2.254"/>
>>     </dhcp>
>>   </ip>
>> </network>
>> 
>> Any idea on what i might be doing wrong?
> 
> Is net.ipv4.ip_forward  set to 0 ?

He left out, and I should hasten to make clear, it *should* be set to 1 
to enable routing:

ken at pirouter:/proc/sys/net/ipv4$ cat /proc/sys/net/ipv4/ip_forward
1

And, also, HOLY CROW, you must be an ASCII charting demigod.  Did you 
use software to make those, or do them yourselves?  Either way, I'm 
impressed...

-Ken