Hi all,Saw a strange one today. Topology simlicity itself: R5 F0/0 is an inside interface on private address space, 10.1.1.1/24. NAT insideR5 F0/1 is a public interface on dummy public address space 1.1.1.1/24, NAT outside. I had one of the Cat switches configured as a dummy host on R5 F0/0, ip address of 10.1.1.100/24 but no DFG set and no routing running. Made sure proxy arp enabled on R5 F0/0I had a second Cat, configured as a dummy host on R5 F0/1 VLAN with public address 1.1.1.254. Again no DFG. The idea was to allow the two to talk to each other, through the router, using NAT to get around the lack of DFG thing. I even remembered a static route to force the inside to outside packet to route before NAT. It did not work as expected. When I pinged from Cat on f0/0 to Cat on f0/1, the ping got as far as Cat on F0/1, but the return had an encapsulation fail. Turns out there was no arp entry for 1.1.1.100 on the second Cat. As a workaround, I ended up putting a secondary IP address on f0/1 of 1.1.1.100 but I don't think I should have had to have done this!! Doing a show ip alias on R5, showed no dynamic entry to 1.1.1.100, despite the NAT statement being clearly there. Printout attached: R5#sh ip int brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 10.1.1.1 YES manual up up FastEthernet0/1 1.1.1.1 YES manual up up R5#sh run | b 0/0 interface FastEthernet0/0 ip address 10.1.1.1 255.255.255.0 ip nat inside ip virtual-reassembly duplex auto speed auto ! interface FastEthernet0/1 ip address 1.1.1.1 255.255.255.0 ip nat outside ip virtual-reassembly duplex auto speed auto R5#sh run | i nat ip nat inside ip nat outside ip nat inside source static 10.1.1.100 1.1.1.100 ip nat outside source static 1.1.1.254 10.1.1.254 ip route 10.1.1.254 255.255.255.255 1.1.1.254 R5#sh ip alias Address Type IP Address Port Interface 1.1.1.1 Interface 10.1.1.1 Dynamic 10.1.1.254 R5#sh ip nat trans Pro Inside global Inside local Outside local Outside global --- --- --- 10.1.1.254 1.1.1.254 --- 1.1.1.100 10.1.1.100 --- --- Has anyone seen this behaviour before? _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
