RE: Re: Debian Sarge Server with iptables behind D-Link Router

Linux Advanced Routing and Traffic Control

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very good. thank you


->
->
-> Hello,
->
-> Le Mercredi 1 Février 2006 23:11, LinuXKiD a écrit :
-> > Some times, I fail to access some HTTPS URLs or MSN service
-> > if you (dlink or router) miss manipulate mtu
->
-> Did you try the TCPMSS netfilter target ?
->
-> For instance :
-> -A POSTROUTING -o ppp0 -p tcp --tcp-flags SYN,RST SYN -m tcpmss
-> --mss \
->    1400:1536 -j TCPMSS --clamp-mss-to-pmtu
-> -A POSTROUTING -o ppp0 -j MASQUERADE
->
-> As you are probably using pppoe on the telephon loop, the
-> maximum transmit
-> unit cannot reach its maximum 1500 bytes.
-> The pppoe header takes 4 bytes.
->
-> You should also let some icmp packets get in in order to have
-> pmtu discovery
-> effective.
->
-> HTH,
->
-> >
-> > andres
-> >
-> >
-> > ->
-> > -> Hi,
-> > ->
-> > -> > try next:
-> > -> > - Put d-link ADSL as "modem"
-> > -> > - Make PPPoE call under Linux
-> > ->
-> > -> Yes I've already tried this - that's my current
-> configuration since one
-> > -> week;)
-> > ->
-> > -> But I want to understand why it's not possible to use the
-> D-Link as a
-> > -> router, and for what kind of problem the tcpdump results stand for.
-> > ->
-> > -> Ralph
-> > ->
-> > -> >
-> > -> >
-> > -> >
-> > -> > ->
-> > -> > -> Hi,
-> > -> > ->
-> > -> > -> I have the shown (end of this post) net work configuration.
-> > -> > ->
-> > -> > -> In a "few" words: My Debian Sarge server is connected to a
-> > -> D-Link ADSL
-> > -> > -> Router (DSL-562T). DMZ is enabled for the Debian Sarge IP
-> > -> on the Router.
-> > -> > ->
-> > -> > -> My Linux server has two NIC's.
-> > -> > -> ethlan = internal Net
-> > -> > -> ethdsl = external -> D-Link
-> > -> > ->
-> > -> > -> My Linux server is configured to make NAT via iptables.
-> > -> > ->
-> > -> > -> Current state - what's working:
-> > -> > -> - Access from internal LAN to Internet is working (http,
-> > -> https, ftp, etc)
-> > -> > -> - Access inside the LAN is working
-> > -> > -> - Access inside the LAN to the linux server is working (http,
-> > https, -> > -> IMAP and SSH)
-> > -> > -> - Access from outside the LAN (from internet) to the
-> Linux server
-> > is -> > -> working for https, IMAP and SSH
-> > -> > ->
-> > -> > -> ***BUT***:
-> > -> > -> Same Problem simular for SSH, https and IMAP:
-> > -> > -> On an internet browser inside the lan I can't access the
-> > -> webserver on
-> > -> > -> the Linux Server when I enter the external URL of the
-> Linux server
-> > -> > -> (dynDNS domain name).
-> > -> > -> The https-page won't be opened. A simple ping to the linux
-> > -> server with
-> > -> > -> the same dynDSN domain name works. Trying to enter the
-> > -> external IP of
-> > -> > -> the linux server in the browser also won't work.
-> > -> > -> The page won't be opened in the browser.
-> > -> > ->
-> > -> > -> Die Seite wird im Browser dann nicht geöffnet.
-> > -> > -> Via telnet auf https ider ssh oder IMAP wird ebenso keine
-> > Verbindung -> > -> aufgebaut, wenn ich als Ziel den dynDSN Domainnamen
-> > angebe. -> > -> Wie gesagt, gebe ich statt des dynDNS Domainnamens den
-> > lokalen Namen -> > -> oder die lokale IP ein, dann geht es.
-> > -> > ->
-> > -> > -> iptables schould log dropped pakets. But there aren't any
-> > -> > -> dropped packets.
-> > -> > -> Ifconfig also does not show any errors (dropped packets)
-> > -> for ethlan /
-> > -> > -> ethdsl.
-> > -> > ->
-> > -> > -> So I've tried to understand what tcpdumd shows for
-> port 443. But
-> > I'm -> > -> bound to say that I'm absolutety not firm with tcpdump.
-> > -> > -> Here's what tcpdump shows:
-> > -> > ->
-> > -> > ->
-> > -> > -> tcpdump for port 443:
-> > -> > -> Not working access from inside the lan to the servers
-> > -> external Name /
-> > -> > -> the servers external IP:
-> > -> > -> => no connection
-> > -> > -> ====================================
-> > -> > -> p54BE15A1.dip0.t-ipconnect.de.https: S
-> 1859848764:1859848764(0) win
-> > -> > -> 65535 <mss 1260,nop,nop,sackOK>
-> > -> > -> 18:43:41.477631 IP lp-java.linkpool.3491 >
-> > -> > -> p54BE15A1.dip0.t-ipconnect.de.https: S
-> 1859848764:1859848764(0) win
-> > -> > -> 65535 <mss 1260,nop,nop,sackOK>
-> > -> > -> 18:43:41.479358 IP p54BE15A1.dip0.t-ipconnect.de.https >
-> > -> > -> lp-java.linkpool.3491: R 0:0(0) ack 1859848765 win 0
-> > -> > -> 18:43:41.967525 IP lp-java.linkpool.3491 >
-> > -> > -> p54BE15A1.dip0.t-ipconnect.de.https: S
-> 1859848764:1859848764(0) win
-> > -> > -> 65535 <mss 1260,nop,nop,sackOK>
-> > -> > -> 18:43:41.969239 IP p54BE15A1.dip0.t-ipconnect.de.https >
-> > -> > -> lp-java.linkpool.3491: R 0:0(0) ack 1 win 0
-> > -> > -> 18:43:42.468301 IP lp-java.linkpool.3491 >
-> > -> > -> p54BE15A1.dip0.t-ipconnect.de.https: S
-> 1859848764:1859848764(0) win
-> > -> > -> 65535 <mss 1260,nop,nop,sackOK>
-> > -> > -> 18:43:42.470116 IP p54BE15A1.dip0.t-ipconnect.de.https >
-> > -> > -> lp-java.linkpool.3491: R 0:0(0) ack 1 win 0
-> > -> > ->
-> > -> > ->
-> > -> > -> tcpdump for port 443:
-> > -> > -> WORKING access from inside the lan to the servers INTERNAL
-> > -> Name / the
-> > -> > -> servers INTERNAL IP:
-> > -> > -> => Successful connection
-> > -> > -> ====================================
-> > -> > -> 18:45:38.773997 IP lp-java.linkpool.3492 >
-> > -> lp-komodo.LINKPOOL.https: S
-> > -> > -> 1505679381:1505679381(0) win 65535 <mss 1260,nop,nop,sackOK>
-> > -> > -> 18:45:38.774478 IP lp-komodo.LINKPOOL.https >
-> > -> lp-java.linkpool.3492: S
-> > -> > -> 189223170:189223170(0) ack 1505679382 win 5840 <mss
-> > -> 1460,nop,nop,sackOK>
-> > -> > -> 18:45:38.774062 IP lp-java.linkpool.3492 >
-> > -> lp-komodo.LINKPOOL.https: .
-> > -> > -> ack 1 win 65535
-> > -> > -> 18:45:38.774608 IP lp-java.linkpool.3492 >
-> > -> lp-komodo.LINKPOOL.https: P
-> > -> > -> 1:106(105) ack 1 win 65535
-> > -> > -> 18:45:38.774660 IP lp-komodo.LINKPOOL.https >
-> > -> lp-java.linkpool.3492: .
-> > -> > -> ack 106 win 5840
-> > -> > -> 18:45:38.813185 IP lp-komodo.LINKPOOL.https >
-> > -> lp-java.linkpool.3492: P
-> > -> > -> 1:1055(1054) ack 106 win 5840
-> > -> > -> 18:45:38.927284 IP lp-java.linkpool.3492 >
-> > -> lp-komodo.LINKPOOL.https: .
-> > -> > -> ack 1055 win 64481
-> > -> > ->
-> > -> > -> Is there any one who can interpret those results? Are
-> these enough
-> > -> > -> informations to see where the problem may ve?
-> > -> > -> Wrong Routing? Linux server iptables problem? Problem
-> > -> inside the D-Link
-> > -> > -> Router?
-> > -> > -> Any suggestions are welcome!
-> > -> > ->
-> > -> > ->      Internet
-> > -> > ->          |
-> > -> > ->         DSL
-> > -> > ->          |
-> > -> > ->          |
-> > -> > ->    D-Link DSL-562T
-> > -> > ->     192.168.200.5
-> > -> > ->          |
-> > -> > ->          |
-> > -> > ->   ------------------------------------
-> > -> > ->   | Dev=ethdsl      Linux Server     |
-> > -> > ->   | 192.168.200.2   lp-komodo        |
-> > -> > ->   |     |                            |
-> > -> > ->   |   route + iptables               |
-> > -> > ->   |     |                            |
-> > -> > ->   | 192.168.240.2                    |
-> > -> > ->   | Dev=ethlan                       |
-> > -> > ->   |-----------------------------------
-> > -> > ->                   |
-> > -> > ->                   |
-> > -> > ->             Switch 10/100/1000
-> > -> > ->                   |
-> > -> > ->                   |
-> > -> > ->   ------------------------------------
-> > -> > ->   |Dev=LAN            Windows Client |
-> > -> > ->   |                   XP Pro SP2     |
-> > -> > ->   |192.168.240.010    lp-java        |
-> > -> > ->   |                                  |
-> > -> > ->   -----------------------------------|
-> > -> > ->
-> > -> > ->
-> > -> > -> Regards,
-> > -> > ->
-> > -> > -> Ralph
-> > -> > ->
-> > -> > -> _______________________________________________
-> > -> > -> LARTC mailing list
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-> > ->
-> > -> _______________________________________________
-> > -> LARTC mailing list
-> > -> LARTC@xxxxxxxxxxxxxxx
-> > -> http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
-> >
-> > _______________________________________________
-> > LARTC mailing list
-> > LARTC@xxxxxxxxxxxxxxx
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->
-> --
-> - Philippe Latu
-> < G N U / Linux >
-> philippe.latu(at)linux-france.org
-> Projet inetdoc.Linux
-> http://www.linux-france.org/prj/inetdoc
-> </>
-> < I U T 'A'  Paul Sabatier >
-> philippe.latu(at)iut-tlse3.fr - 05.62.25.80.28
-> Enseignant/Chargé de mission Systèmes & Réseau
-> </>
->
-> _______________________________________________
-> LARTC mailing list
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