I have a CISCO 1720 with one interf

[nirina]

I have a CISCO 1720 with one interface card (Fastethernet0).

My configuration is:
interface FastEthernet0

ip address 192.168.0.254 255.255.255.0 secondary
ip address 62.56.162.28 255.255.255.240
ip nat inside
!
ip route 0.0.0.0 0.0.0.0 62.56.162.30


I want to do NAT with this one interface(Fastethernet0) with network address 62.56.162.28.
My network lan is: 192.168.0.0/24
My network wan is: 62.56.162.16/28


It's not working.
What do I do please?

Claude

 

[BuckWeet]

You really need 2 ethernet interfaces. Because you have to designate 1 interface to be the "outside" and one for the "inside" You can buy a WIC-1ENET (ethernet module) for the 2nd WIC port and then do your NAT'ing easily with it..

BuckWeet

 

[omartin]

Hi,

You need to use a loopback interface to do this and also policy based routing. There is a sample on cisco`s web site, but here is approximately what you need to do.

1) Mark the Ethernet interface as an inside nat interface (ip nat inside)
2) create a loopback address, mark this interface as outside (ip nat outside)
3) create a policy in order to reroute all trafic destined for the default route to to go the loopback address before following the routing table (ip policy ...).

This is also called NAT on a stick if you are looking for info on this on cisco's site.

Olivier Martin
Router administrator

 

[BuckWeet]

Heh, talk about ugly.. I bet that is really CPU intensive, do you have any proc usage information when using this?

BuckWeet

 

[omartin]

Well, there will be a raise in CPU use as compared with no NAT, but it still should be comparable as a standard NAT. With IP route caching being enabled (using cef or whatever), there should not be that much of an overhead as all trafic is routed to the virtual interface which forwards it back out. Conceptually, there is a single more hop, and since typical internet link are not superfast, this should not become a problem. Of course, with a DS3 link, this might become a bottleneck on this kind of box. But again, I don't think a 1720 is the router to get on a DS3 Olivier Martin
--------------
Read that somewhere and I think its cool :
If you want to accelerate a Windoze Box, there is an easy way to have it accelerate at -9.8 m/s^2

 

[rcasta]

You could also try using subinterfaces and, of course, a switch/trunk-port with 2 vlans.

int fastethernet0
encapsulation dot1q

int fastethernet0.1
ip address 192.168.0.254 255.255.255.0
ip nat inside

int fasteth0.2
ip address 62.56.162.28 255.255.255.240
ip nat outside

It worked for me =)

best regards,

 

[BuckWeet]

Since when can a 1720 do 802.1q???

1721's can, but not 1720's (unless they came out with a new version within the last few months)


BuckWeet