connecting a dsl modem/router to a cisco router.

[Reprovoid]

Hi.

  I've connected a dslmodem/router to one of the ethernet Interfaces on a cisco router.I've given the Interface an address In the modem/routers range.I didn't use dhcp.If I create a default route on this Interface would I be able to ping an address(no dns names , Just the ip address) on the web the same way a host pc would be able to? I haven't used nat translation or anything else.I would like to understand why I would or wouldn't be able to ping an external address via the dsl modem/router.

Thanks , sorry for my wording If I'm not being clear

[Neeraj Arora · Accepted solution]

yes, you would be able to ping an Internet/Public ip from the router if you have a default route pointing towards the DSL modem, just like a PC.

till this point NAT would not be required as you are basically using this router as a PC/Node, but if you connect another segment behind this router(obviously which would have its own ip subnet) and from there you try to access internet, then YES NAT would be needed

Check this thread, it has a similar topology that you might be looking for:

https://supportforums.cisco.com/thread/2131026?tstart=0

HTH

Neeraj

[Reprovoid]

Hi.Thank you!

I have one more question.Why does a default route work when you use the next hop router but doesn't when you use the outgoing Interface like you could with a static route?

[cadet alain · Accepted solution]

Hi,

when you configure a static route with an outgoing interface then the router thinks all destinations are reachable out this interface and so when doing the L3 to L2 mapping it will do an ARP or InARP request for the final destination, if the interface is ethernet it can work if the next-hop is doing proxy-arp but it is not recommended.if the interface is a Frame-Relay multipoint interface then it won't work as proxy InARP is not supported on Cisco routers.

So  only configure a static with outgoing interface on point-to-point interfaces and for multipoint specify the next-hop or the next-hop and outgoing interface if you want to save a recursive lookup.

Regards.

Alain

[Reprovoid]

Thankyou!