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Dial-up versus LAN connection

Occasional Advisor

Dial-up versus LAN connection

Hi all,

my problem is the following.
I have a system made up by these components:

PC A--> Router A (NAT) ---> Router B ---> PC B

PC A and Router A belong to the same LAN1.
Router B belongs to LAN2 and accepts only a given range of addresses not belonging to LAN1. Router B nats correctly source addresses coming from LAN1 into the given range of admitted addresses.
When inserted into LAN1, PC A can ping PC B, its address being correctly natted by router B.

Yet when using a dial-up connection landing on a Linux machine acting as a RAS, PC A gets an address from LAN1 ... BUT it cannoct reach destination PC B.

Is this a mystery? I suspect it depends on the configuration of the Linux machine (RAS).

Could you help me with some hints?

Thanks in advance,

Ron Kinner
Honored Contributor

Re: Dial-up versus LAN connection

Can PC A ping Router A when dialed up?

What does

netstat -rn

look like on PC A?

Are you positive that router B's NAT source list includes PC A's RAS address? (And that PC B knows how to get to them?)

Could someone have squatted on the IP addresses assigned by RAS? Had that happen where I work. Of 12 addresses in the RAS pool, 6 were occupied by squatters (people would ping an address and if no response assume it was vacant). Try pinging all addresses from a device on A when the RAS does not have any calls.

Does the linux box do any filtering? IPCHAINS or the like?

Occasional Advisor

Re: Dial-up versus LAN connection

Thanks Ron for the reply!

I found the solution myself and it was simply depending on the fact that no routes to PC B had been set on the RAS Linux machine... Once I provided the RAS with this information, everything turned up right! (PC A could ping router A when connected via dial-up and the range of available addresses was very large [an entire subnet!])

Thank you anyway for the list of possible causes! Always useful!