Sharing an IP Gateway on multiple Subnets

Question

Hi
I'm flamboozled with something that doesn't seem like it should be so hard on a Solaris 10 11/06 webserver with sparse zones...
I have 4 different subnets:
A.B.C.0/29, D.E.F.0/29, G.H.I.0/29 etc.
Only one of them currently has a gateway address, and I put the global's IP there leaving 4 address that indeed work fine for with sparse zones...
I have some ideas, but I'm hoping someone can help point me in the right direction.
1.) Setup NAT, as per http://blogs.sun.com/edp/entry/using_branded_zones_on_a if that works on Solaris 10.
2.) Try some adaptation of:
http://meljr.com/~meljr/Solaris10LocalZoneDefaultRoute.html
Where you boot into global without the local zone running. Setup a network interface complete with a default route, remove the network interface in question, and boot the zone that then uses that network interface.
It uses:
server-a# ifconfig qfe1 addif XXX.YYY.ZZZ.34/24 up
server-a# route add default XXX.YYY.ZZZ.1
server-a# ifconfig qfe1 removeif XXX.YYY.ZZZ.34
It seems like this should work, but nothing I've tried routes the packets correctly.
A problem here is I'm not trying to separate the networks, so the default already exists (and route tells me so) but the default is not "passed" into my local zone since it's on a different subnet.
4.) arp
I've statically rewired the A.B.C.1 address to use the single gateway's 6 byte hex address, but that doesn't work.
5.) Zone permissions
I understand that I may be able to give my zone special permissions... I have yet to try this in detail.
6.) Rework the network to get 4 gateway address, and probably 4 IP address for the global account.
I have to think that this isn't that unusual of a situation. Can anyone share their setup or ideas on how I could do this?
Thanks
newbiep

Answer 1

It's not that it's necessarily unusual, it's that the design requirements of zones don't make this easy.
The TCP layer was an easy point for zones to hook into. So much of the TCP layer is separated, but the IP layer is not. Zones do not have their own routing and cannot affect the routing of the global zone. So complex routing issues are just hard to deal with.
Your #2 should work, but I don't have specific suggestions or anything.
"IP instances" is part of the crossbow project that will create separate IP stacks for zones (if you want), so things like this are much simpler if you're dedicating an adapater or VLAN to a zone. It's not yet available though.
Darren