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Special Forums IP Networking Why eth1 with auto dhcp disturbs pppoe over eth0? Post 302995964 by bakunin on Sunday 16th of April 2017 05:27:11 AM
Old 04-16-2017
Quote:
Originally Posted by adrhc
eth1 is plugged in a LAN port of a router with its WAN port unplugged (yeah, don't ask why). When setting a manual ip on eth1 while gateway and dns are left blank the websites are accessible in browser again.
You have already said it: DHCP (dynamic host configuration protocol) is a method of not only setting an IP address but to configure the whole IP stack of a system: this includes (but is not limited to:

- IP adresses
- subnet masks
- static routes
- name resolution

What exactly you get from the DHCP-server is configured there, not your system and chances are the DHCP-server is just configured badly.

So, if you connect to your first DHCP-server on eth0 you get everything configured right and your browsing is working. The second DHCP-server is perhaps configured the same way but because there is no outside connection you cannot use what it configures on your system and therefore the configuration is wrong and if you use that your working config is overwritten by a not-working config. Actually, you can use the IP-address you get, but not the DNS server and/or static routes that come along with it.

Configure the DHCP for your second interface for "DHCP (addresses only)" so that it doesn't overwrite the content of your file /etc/resolv.conf when configuring an IP address. Otherwise get the DHCP-server configured correctly so that it doesn't send certain "option fields" (DHCP-terminology) or fill them with values which work.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
 

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PPPOE-SNIFF(8)                                                System Manager's Manual                                               PPPOE-SNIFF(8)

NAME
pppoe-sniff - examine network for non-standard PPPoE frames SYNOPSIS
pppoe-sniff [options] DESCRIPTION
pppoe-sniff listens for likely-looking PPPoE PADR and session frames and deduces extra options required for pppoe(8) to work. Some DSL providers seem to use non-standard frame types for PPPoE frames, and/or require a certain value in the Service-Name field. It is often easier to sniff those values from a machine which can successfully connect rather than try to pry them out of the DSL provider. To use pppoe-sniff, you need two computers, a DSL modem and an Ethernet hub (not an Ethernet switch.) If the DSL modem normally connects directly to your computer's Ethernet card, connect it to the "uplink" port on the Ethernet hub. Plug two computers into normal ports on the hub. On one computer, run whatever software the DSL provider gave you on whatever operating system the DSL provider supports. On the other computer, run Linux and log in as root. On the Linux machine, put the Ethernet interface into promiscuous mode and start pppoe-sniff. If the ethernet interface is eth0, for exam- ple, type these commands: ifconfig eth0 promisc pppoe-sniff -I eth0 On the other machine, start your DSL connection as usual. After a short time, pppoe-sniff should print recommendations for the value of PPPOE_EXTRA. Set this value in /etc/ppp/pppoe.conf. If pppoe-sniff indicates that something special is required in PPPOE_EXTRA, please e- mail this to pppoe@roaringpenguin.com along with the name of your ISP and the manufacturer and model number of your DSL modem. This infor- mation will be collated and provided on the PPPoE web page for users who do not have two computers. After pppoe-sniff finishes (or you stop it if it seems hung), remember to turn off promiscuous mode: ifconfig eth0 -promisc OPTIONS
-I interface The -I option specifies the Ethernet interface to use. Under Linux, it is typically eth0 or eth1. The interface should be "up" and in promiscuous mode before you start pppoe-sniff. -V The -V option causes pppoe-sniff to print its version number and exit. BUGS
pppoe-sniff only works on Linux. AUTHORS
pppoe-sniff was written by David F. Skoll <dfs@roaringpenguin.com>. The pppoe home page is http://www.roaringpenguin.com/pppoe/. SEE ALSO
pppd(8), pppoe(8), pppoe-sniff(8), pppoe-relay(8), /usr/share/doc/pppoe/README.Debian.gz 4th Berkeley Distribution 3 July 2000 PPPOE-SNIFF(8)
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