[quagga-users 6960] Unnumbered interfaces and OSPF

[Aron Brand]

Hi,

Has anyone managed to get quagga to succesfully OSPF with a Cisco router (or
another Quagga) having unnumbered interfaces ? Are unnumbered interfaces
supported at all by Quagga ? I found some minor references to unnumbered
interfaces in the code, but nothing in the documentation .

Thanks
Aron

[Andrew J. Schorr]

Hi Aron,

Post by Aron Brand
Has anyone managed to get quagga to succesfully OSPF with a Cisco router (or
another Quagga) having unnumbered interfaces ? Are unnumbered interfaces
supported at all by Quagga ? I found some minor references to unnumbered
interfaces in the code, but nothing in the documentation .

This has been discussed before, please check the archives. But basically
the question is what do you mean by an unnumbered interface? In IOS,
they have "unnumbered" interfaces, but this basically means that the interface
should borrow an address from another interface (so the interface
actually has an address, but it's a shared address, not unique).
In the case of quagga, it works fine to have point-to-point interfaces
that have a shared local address, as long as the remote peer address
is unique. Are you trying to do something different than this?

Regards,
Andy

[Aron Brand]

Andrew,

Thanks for your response.
Yes, I was referring to the case where the unnumbered interface borrows the
IP address of another interface.

The issue is, as far as I can understand, it does need special handling by
Quagga. When working with an unnumbered interface, when Quagga learns a
route on this interface, it needs to create the route using the interface
name, and not the interface IP address (since this IP address is shared
between multiple interfaces).

According to the Cisco FAQ,

"

A router receiving a routing update installs the source address of the
update as the next hop in its routing table. Normally, the next hop is a
directly-connected network node. This is no longer the case if we use IP
unnumbered because each serial interface "borrows" their IP address from a
different LAN interface, each in a different subnet and possibly in a
different major network. When IP unnumbered is configured, routes learned
through the IP unnumbered interface have the interface as the next hop
instead of the source address of the routing update. Thus we avoid an
invalid next hop address problem due to the source of the routing update
coming from a next hop that is not directly connected.

"
Did you succeed to make an unnumbered link work between two Quagga
instances, or between Quagga and a Cisco router ?

Thanks a lot for your help,
Aron

Post by Andrew J. Schorr
Hi Aron,

Post by Aron Brand
Has anyone managed to get quagga to succesfully OSPF with a Cisco router

(or

Post by Aron Brand
another Quagga) having unnumbered interfaces ? Are unnumbered interfaces
supported at all by Quagga ? I found some minor references to unnumbered
interfaces in the code, but nothing in the documentation .

This has been discussed before, please check the archives. But basically
the question is what do you mean by an unnumbered interface? In IOS,
they have "unnumbered" interfaces, but this basically means that the interface
should borrow an address from another interface (so the interface
actually has an address, but it's a shared address, not unique).
In the case of quagga, it works fine to have point-to-point interfaces
that have a shared local address, as long as the remote peer address
is unique. Are you trying to do something different than this?
Regards,
Andy

[Andrew J. Schorr]

Hi Aron,

Post by Aron Brand
Yes, I was referring to the case where the unnumbered interface borrows the
IP address of another interface.

OK, that should work fine, as long as the peer address is unique.

Post by Aron Brand
The issue is, as far as I can understand, it does need special handling by
Quagga. When working with an unnumbered interface, when Quagga learns a
route on this interface, it needs to create the route using the interface
name, and not the interface IP address (since this IP address is shared
between multiple interfaces).

This should not be a problem. Quagga should manipulate the kernel routing
tables properly in this situation.

Post by Aron Brand
Did you succeed to make an unnumbered link work between two Quagga
instances, or between Quagga and a Cisco router ?

I have done it between two quagga instances. But I have not done it between
quagga and a cisco router...

Regards,
Andy