double nat and ip helper addess

[John Cheetley]

Hi Team,

Have resolved double nat issue by using DMZ and tested working OK thanks to Paul Driver and Georg Pauwen

Was looking for articles on forum re ip helper address for ROAS scenario for Layer 2 switch and possibly some examples

Found couple re double nat resolution issues but nothing re ip helper

[Georg Pauwen · Accepted solution]

Hello,

ROAS as in router-on-a-stick ? You need the IP helper address on all subinterfaces (only if you are using an external DHCP server and not the IOS DHCP server).

Can you elaborate on your double NAT/IP Helper setup ?

[John Cheetley]

Hi Georg,

Thanks for quick reply

I placed the router IP into the DMZ on the ISP router and done traceroute from CUCM GUI to 8.8.8.8 and connects

Have disabled DHCP on IOS and CUCM and using from ISP router only. So I guess in theory is same network. Strangely though. Though I have added the router mac address to ARP table in 2924 switch, saved via copy run start, rebooted. run sh arp..the table is updated with IP and mac address

sh cdp neighbors shows router connected via trunk on port 24 of switch.