Odd tcp dump? was: ssh working with dialup, not through router

M. Fioretti mfioretti at mclink.it
Tue May 18 20:27:49 UTC 2004

On Sat, May 15, 2004 18:33:21 PM -0700, Tom 'Needs A Hat' Mitchell
(mitch48 at sbcglobal.net) wrote:
> Does ping interact with the far machine in both directions.
> i.e. check "ping -R" and "traceroute" for strange things.

ping -R gives no error I can see. traceroute goes like this:

/usr/sbin/traceroute the.ssh.server
traceroute to the.ssh.server (its.ip.address), 30 hops max, 38 byte packets
 1 (  0.809 ms  0.708 ms  0.695 ms
[intermediate steps cut]
15  FE1.internet9t.9massy1-1-ro-bas-2.9tel.net (  77.582 ms  79.149 ms  79.839 ms
16  * * *
[on like this until...]
27  * * *
28  * * *
29  * * *
30  * * *

Note that this particular machine (the one I should really log into
urgently) is a dyndns machine, but I do have the same behavior on
really static IP addresses.

> Are you using RFC 1918, ...Private Internet numbers behind the
> router?  Remember that these nets are not routeable!

I know about private numbers, but that's what the ADSL modem/router
device (D-Link DSL-504T) should take care of. My ISP recommends that
router model, told me to set everything like this (ie static, private
IPs in the home LAN), and confirmed they are not blocking any
ports. And I *can* surf and email without problems.

> Getting into a RFC1918 net should not be facilitated via routes
> except via a single NAT port mapping sort of connection.

As far as I understand, this is exactly what the router box is
(supposed to be) doing.

> Can your ADSL router act in NAT mode?

It says that NAT is on (in its web config interface).

> Lastly make sure that DNS is correct, other have addressed this (pun
> intended).

Even here, I can't find anything wrong.

Any other help/comment/request of further tests is more than welcome.
Thank you all in advance!

Marco Fioretti

Marco Fioretti                 m.fioretti, at the server inwind.it
Red Hat for low memory         http://www.rule-project.org/en/

Never let your sense of morals prevent you from doing what is right
                                           Salvor Hardin , "Foundation"

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