[quagga-users 14956] Hiding subnet along routing path

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Hi.

I have a question regarding OSPF operation in some specific route
configuration.

Let's say I have two devices, each has 2 network interfaces and both
running OSPF.

----------------------------    --------------------------|
| DEV1                     |    | DEV2                    |
| eth0                 eth1|<==>|eth1                 eth0|
| 192.168.0.1 192.168.192.1|    |192.168.192.2 192.168.1.1|
----------------------------    ---------------------------

The "default" kernel routes are like:
DEV1:
192.168.192.0/24 dev eth1 proto kernel scope link src 192.168.192.1
192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.1
DEV2:
192.168.192.0/24 dev eth1 proto kernel scope link src 192.168.192.2
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.1

OSPF and route distribution works as expected through this network.

Now, I wanted to hide the eth1 subnet from the outside world by
setting 192.168.192.0/24 route source to eth0 IP address, like:
DEV1:
192.168.192.0/24 dev eth1 scope link  src 192.168.0.1
DEV2:
192.168.192.0/24 dev eth1 scope link  src 192.168.1.1

This works from routing perspective, but it breaks OSPF. This is
probably expected, since this has broken a link between two
devices/neighbors.

My question is if it is possible to somehow configure OSPF to
work with those modified route sources? To be able to exchange
OSPF messages by hopping over eth1 subnet?

Thank you very much.

RegK

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<div dir=3D"ltr"><div><div><div><div><div><div><div><div><div><div><div><di=
v><div><div><div>Hi.<br><br></div>I have a question regarding OSPF operatio=
n in some specific route configuration.<br><br></div>Let&#39;s say I have t=
wo devices, each has 2 network interfaces and both running OSPF.<br><br><fo=
nt face=3D"monospace,monospace">----------------------------=C2=A0=C2=A0=C2=
=A0 --------------------------|<br></font></div><font face=3D"monospace,mon=
ospace">| DEV1=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0=C2=A0=
=C2=A0 | DEV2=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |<br></font></div><f=
ont face=3D"monospace,monospace">| eth0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 eth1|&lt;=3D=3D&gt;|eth1=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 eth0|<br>| 192.168.0.1 192.168.192.1|=C2=A0=C2=A0=C2=A0 |192.168.192.2 =
192.168.1.1|<br>----------------------------=C2=A0=C2=A0=C2=A0 ------------=
---------------<br><br></font></div><font face=3D"monospace,monospace">The =
&quot;default&quot; kernel routes are like:<br>DEV1:<br><a href=3D"http://1=
92.168.192.0/24">192.168.192.0/24</a> dev eth1 proto kernel scope link src =
192.168.192.1 <br><a href=3D"http://192.168.0.0/24">192.168.0.0/24</a> dev =
eth0 proto kernel scope link src 192.168.0.1<br>
<font face=3D"monospace,monospace">DEV2:<br><a href=3D"http://192.168.192.0=
/24">192.168.192.0/24</a> dev eth1 proto kernel scope link src 192.168.192.=
2 <br><a href=3D"http://192.168.1.0/24">192.168.1.0/24</a> dev eth0 proto k=
ernel scope link src 192.168.1.1</font>

<br><br></font></div><font face=3D"monospace,monospace">OSPF and route dist=
ribution works as expected through this network.<br><br></font></div><font =
face=3D"monospace,monospace">Now, I wanted to hide the eth1 subnet from the=
 outside world by<br></font></div><font face=3D"monospace,monospace">settin=
g <a href=3D"http://192.168.192.0/24">192.168.192.0/24</a> route source to =
eth0 IP address, like:<br>
<font face=3D"monospace,monospace">DEV1:<br><a href=3D"http://192.168.192.0=
/24">192.168.192.0/24</a> dev eth1 scope link=C2=A0 src 192.168.0.1 <br>
<font face=3D"monospace,monospace">DEV2:<br><a href=3D"http://192.168.192.0=
/24">192.168.192.0/24</a> dev eth1 scope link=C2=A0 src 192.168.1.1<br><br>=
</font></font></font></div><font face=3D"monospace,monospace"><font face=3D=
"monospace,monospace"><font face=3D"monospace,monospace">This works from ro=
uting perspective, but it breaks OSPF. This is<br></font></font></font></di=
v><font face=3D"monospace,monospace"><font face=3D"monospace,monospace"><fo=
nt face=3D"monospace,monospace">probably expected, since this has broken a =
link between two<br>devices/neighbors.<br><br></font></font></font></div><f=
ont face=3D"monospace,monospace"><font face=3D"monospace,monospace"><font f=
ace=3D"monospace,monospace">My question is if it is possible to somehow con=
figure OSPF to<br></font></font></font></div><font face=3D"monospace,monosp=
ace"><font face=3D"monospace,monospace"><font face=3D"monospace,monospace">=
work with those modified route sources? To be able to exchange<br></font></=
font></font></div><font face=3D"monospace,monospace"><font face=3D"monospac=
e,monospace"><font face=3D"monospace,monospace">OSPF messages by hopping ov=
er eth1 subnet?<br><br></font></font></font></div><font face=3D"monospace,m=
onospace"><font face=3D"monospace,monospace"><font face=3D"monospace,monosp=
ace">Thank you very much.<br><br></font></font></font></div><font face=3D"m=
onospace,monospace"><font face=3D"monospace,monospace"><font face=3D"monosp=
ace,monospace">RegK<br></font></font></font></div>

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