[LiSA-Users] Lisa supports sub-interfaces?

[Radu Rendec]

Hi,

First of all, most of LiSA code is Layer 2. All Layer 3 functions are
accomplished through the original linux ip stack. In fact, all we did
was implement per-vlan virtual interfaces and this is all that's
necessary to do inter-vlan routing - the linux routing code takes care
of the rest.

Since LiSA tries to mimic Cisco switches (rather than routers) you
should think of it as a Cisco Layer 3 switch. So it basically behaves
like a switch, but you can assign ip addresses to more than one vlanX
interface and do routing between those interfaces.

Going back to your configuration, you can't create subinterfaces, but
you can configure the physical interface of the linux box in trunk mode
and use vlanX (virtual) interfaces for Layer 3.

Since you have only one NIC in each linux box, you don't need LiSA at
all because there's nothing to *switch* packets between. You could use
instead the 8021q kernel module along with it's userspace companion,
vconfig. This allows for 802.1q trunking and, for instance, if you have
eth0 for the NIC, you can create eth0.2 and eth0.3 which will operate
with untagged packets on vlan 2 and 3 respectively.

I'm not familiar with other distro's init scripts, but on RedHat and
friends you can even have the eth0.X interfaces brought up automatically
at system startup with minimal effort.

Going back to your routing issue, you can't have more than one default
route in a routing table, but you can have more than one routing
table ;) Then you can configure what routing table to look at depending
on the source network of the packet. The key to this approach is in the
following command families:

ip rule ... -> inspect or configure policy routing rules
/etc/iproute2/rt_tables -> define routing table names
ip route ... table ... -> manipulate routes in a specific table

I don't know if this is all supported by the standard init scripts, you
might have to put all the comands in a script and have it run
from /etc/rc.local.

If you still want to use linux for your project, then you should
definitely have a look at LARTC (http://lartc.org/howto/), especially at
chapter 4.

I hope this answers your questions.
Best regards,

Radu Rendec

On Sat, 2009-01-10 at 07:59 -0800, Luis wrote:
> Hi,
> 
>  
> 
> I’m thinking of using Lisa at work to deploy across a fleet of 50+
> Linux boxes, one per building in my company such that I can remotely
> ssh to each Linux box, and test each of my building’s LANs. My ideal
> requirements are as follows:
> 
>  
> 
> 1)       Have a single Linux box per building (all buildings are WAN
> meshed across a private WAN via Telco)
> 
> 2)       Each Linux box to have 1 NIC
> 
> 3)       Each Linux box would use 802.1q trunking, with about 9 VLANs
> and 1 subnet per VLAN. Trunking would be done to a single port of a
> LAN 3COM switch.
> 
> 4)       Each subnet would be unique, and each subnet would need its
> own unique gateway IP address (this is the main reason I’m wanting to
> try Lisa. I’ve had a heck of a time trying to get the standard Linux
> routing table to accept and route different subnets to different
> gateways, possibly I was doing something wrong).
> 
>  
> 
> I am fairly familiar with Cisco switches and routers, and in
> Cisco-land I would simply create a bunch of subinterfaces under a
> single physical port, configure a bunch of VLANs in the global config
> and subnets per VLAN, and add a bunch of static routes for each
> gateway IP per subnet.
> 
>  
> 
> The big question I have is: Can Lisa support subinterfaces and allow
> for a routing table to have multiple gateway IP addresses?(one per
> subnet), beyond just a routing table with a default route like what
> Linux without Lisa seems to do?
> 
>  
> 
> If subinterfaces are not supported, could you possibly point to a way
> of accomplishing my goals above with Linux?
> 
>  
> 
> Thanks a lot!
> 
>  
> 
> Luis
> 
>  
> 
> PS. Suggestion: Your Documents webpage could really use a user manual
> so people can tell what commands are supported. The screenshots don’t
> show everything.
> 
>  
> 
> 
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