Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


Eth0 only partly there...

Posted on 1997-08-15
Medium Priority
Last Modified: 2010-03-17
I thought perhaps you might beable to help with a problem
here that seems to have all the "guru's" I have consulted stumped.
Here''s the layout:
Linux darkstar 2.0.23 #3 Fri Jun 6 20:52:07 CDT 1997 i586  I have the linux machine here, on ppp0, with a 3com 509b card <called eth0.  The inside net has a win 3.11 and a win95 machine, and, both set with <blackhole> as their gateway.  I can watch all the packets on with various net tools, incuding tcpdump.  the win machines can play togeth fine.  but, blackhole will not recognize their packets, and they seem to not see those of blackhole.  So, there at this point is nothing getting masqueraded out.  All policies for ipfw are accept, to make it as open as possible now.    <damn, the buffered space here is hardly adequate to give a proper rundown of what is really being observed over ehre, sorry>
Question by:smokie
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Expert Comment

ID: 1586122
Really, I'd need to see the output of ifconfig, route and ipfwadm -Fl.

Assuming there is no problem with netmasks and routes... It is of course possible that there is a hardware problem... I have seen a card which could recieve but not transmit....


Author Comment

ID: 1586123
eth0      Link encap:10Mbps Ethernet  HWaddr 00:20:AF:04:4C:42
          inet addr:  Bcast:  Mask:
          RX packets:4902 errors:4 dropped:4 overruns:0
          TX packets:86 errors:0 dropped:0 overruns:0
          Interrupt:10 Base address:0x300
A bad card was considered, but, card swaps produce the same results.  As for the ipfwadm rules, aren't we getting ahead of ourselves on that?  ipfwadm with no rules set leaves it a wide open accept policy, and pinging the internal interface from within the internal net should work according to the FAQ's surrounding this type of setup, yes?

Expert Comment

ID: 1586124
Yes ping should work to or from the internal network.
Have you setup a route?
route add -net netmask eth0
Have you looked at the ip masquerade howto:
And the net3 howto(the internal network should be working first):

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.


Expert Comment

ID: 1586125
Can you ping the ethernet interface of your linux box from a win95 box on the local network?

Can you telnet to it?

If you can't, the problem is with your basic networking setup - post the output of a route -n please.

If the above tests work, then does the machine route properly? If not, have you actually recompiled the kernel with IP routing support? Are you booting from your recompiled kernel?


Author Comment

ID: 1586126
Kernel routing table
Destination     Gateway         Genmask         Flags MSS    Window Use Iface   *      UH    1500   0        0 ppp0    *        U     1500   0        8 eth0       *            U     3584   0      117 lo
default   *               UG    1500   0       44 ppp0
Nope, the win machines talk fine to one another, but, even though the linux box can see traffic on the wire, it's packets don't make it to the win boxes properly, nor do the win boxes talk completely to the linux box.  And, even with the ppp0 interface down, there are no changes.  If anyone would like to request it, I have tcpdump traces I will be happy to e-mail to anyone.  This issue has been a pain for far too long here, and has stumped every guru we have contacted.  All are stumped...

Expert Comment

ID: 1586127
Have you defined any firewalling/maquering parameters after booting the kernel ? If so, can you try not to define them, and then try to contact the other hosts ? Are you sure that the problem isn't with the Win-machines configuration ?

Author Comment

ID: 1586128
As stated, not ipfwadm rules are setup, the default policy is accept, the win boxen talk fine to one another, the linux box sees all traffic on the eth0 interface, yet, the win boxen and the linux box seem to talk improperly to one another.  The win boxen have the linux box as their gateway, and seek to do dns from the host files on those machines and via the resolve setup of the linux box...

Expert Comment

ID: 1586129
Try updating the kernel to 2.0.29 NOT 2.0.30.
I've got several machines linked via ethernet and 56k bridges and masqerade works fine. The 2.0.30 kernel at times stopped forwading packets but when I backed off to 2.0.29 the other day the problems cleared. 2.0.31 Is due out real soon and promises to fix all this and be released code, not experimental.


Author Comment

ID: 1586130
am about to try this.  Have held off as I was under the impression that 2.0.23 had everything in place, though not as many ip-masq modules available.  Have asked repeatedly if there was a bug in 2.0.23 that caused the troubles I see here, but have as yet gotten no info to suggest this.  Thing is, there were so may reports of folks succeeding with the earlier 2.0.x and previous kernels, I have been looking for info to suggest that there's something drastically wrong with the earlier kernels.

Accepted Solution

nicademus earned 340 total points
ID: 1586131
Have you ever compiled the kernel and wondered about using the option in the Networking section of the config which enables PC/TCP compatibility mode?

Best bet though is to upgrade to 2.0.29 and also enable the PC/TCP compat. feature.

Featured Post

Interactive Way of Training for the AWS CSA Exam

An interactive way of learning that will help you visualize core concepts so that you can be more effective when taking your AWS certification exam.  Built for students by a student to help them understand the concepts that they are being taught.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have seen several blogs and forum entries elsewhere state that because NTFS volumes do not support linux ownership or permissions, they cannot be used for anonymous ftp upload through the vsftpd program.   IT can be done and here's how to get i…
Note: for this to work properly you need to use a Cross-Over network cable. 1. Connect both servers S1 and S2 on the second network slots respectively. Note that you can use the 1st slots but usually these would be occupied by the Service Provide…
If you're a developer or IT admin, you’re probably tasked with managing multiple websites, servers, applications, and levels of security on a daily basis. While this can be extremely time consuming, it can also be frustrating when systems aren't wor…
In this brief tutorial Pawel from AdRem Software explains how you can quickly find out which services are running on your network, or what are the IP addresses of servers responsible for each service. Software used is freeware NetCrunch Tools (https…
Suggested Courses

670 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question