how about subneting it? can you change the router, if not you need to set the proxy arp feature for the external card.
let's say you have x.y.z.0/24 then split it in x.y.z.0/25 for your external interface and x.y.z.128/25 for your DMZ. If you can't change the router, activate proxy arp on the external NIC.
You can split in more networks of course, this way you loose more IPs, but you can also get more behind the firewall.
how about subneting it? can you change the router, if not you need to set the proxy arp feature for the external card.
let's say you have x.y.z.0/24 then split it in x.y.z.0/25 for your external interface and x.y.z.128/25 for your DMZ. If you can't change the router, activate proxy arp on the external NIC.
You can split in more networks of course, this way you loose more IPs, but you can also get more behind the firewall.