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plate
Bodhisattva
Joined: 25 Jul 2002
Posts: 1663
Location: Berlin
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 Posted: Tue Mar 04, 2003 1:09 pm Post subject: Two NICs, two DHCP? Portable networking questions |
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Two NICs in my Vaio:
- eth0: built-in NIC, e100 kernel support, iface_eth0="dhcp"
- wlan0: Orinoco Silver, drivers from the pcmcia-cs package
I installed the WiFi with a fixed IP for iface_wlan0 just to see if I could get it running at all, but I can't test anything here at home (no AP around). Subsequently I would much rather have the wireless NIC look for a DHCP server in the vicinity, too. I guess that's not a problem as long as one or the other NIC is down, but what if not? Can the same DHCP client watch two NICs? Are two clients started if both NICs are active? And, frankly, what happens to /etc/resolv.conf? Are they going to fight over it?
And a bonus question: If the boot-time eth0 setup fails because it's unplugged, is there any way to tell the DHCP client not to bother trying on a device that doesn't have a link? Like sending ARP packets, not getting anything back, and telling DHCP about it? Trying to minimize the wait when booting... |
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spinfire
n00b
Joined: 07 Feb 2003
Posts: 38
Location: Newmarket, NH
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| Posted: Tue Mar 04, 2003 2:51 pm Post subject: My setup |
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I have gentoo installed on my HP zt1000, and I have a similar interface arrangement.
eth0 is the builtin rtl8139wired network, used for installation and configured for DHCP.
wlan0 is a Linksys Prism2-based card running with the linux-wlan-ng drivers. wlan0 is also configured for DHCP.
At home, I use the wireless unless I am right near a network jack. On bootup, I don't bother to bring net.eth0 up at all. When you plug in the pcmcia card or start pcmcia_cs, net.wlan0 is started with dhcp.
If I want to use the wired connection for some reason: I unplug the pcmcia card to bring down wlan0 and bring net.eth0 up. |
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Sven Vermeulen
Retired Dev
Joined: 29 Aug 2002
Posts: 1345
Location: Mechelen, Belgium
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| Posted: Tue Mar 04, 2003 3:01 pm Post subject: |
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You can tell your dhcp-client to use DHCP on a particular nic:
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~# dhcpcd -i eth0
~# dhcpcd -i wlan0
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I think that Gentoo does this automatically (cannot check it right now).
A DHCP-server gives you information about routing and dns-servers. If both DHCP-servers think they "own" the network (i.e. they both set DNS and default gateway) then the last runned dhcpcd will prevail.
Normally, in an environment with multiple DHCP-servers, one of them sets the default gateway (for internet), the other one only sets the routing for his own network. DNS should, on both DHCP-servers, be the same.
However, if this is not the case, then you probably want to make a working /etc/resolv.conf immutable:
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~# chattr +i /etc/resolv.conf
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ef11
n00b
Joined: 07 Jan 2003
Posts: 16
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| Posted: Thu May 08, 2003 9:14 pm Post subject: Can't eth0 OR eth1 provide the net virtual service? |
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I have a laptop and have built in eth0 and can add a pcmcia wireless network card.
I have been reading about pcmcia installations and am planning on trying to get the wireless pcmcia card working. This above thread has me puzzeled, though.
I thought gentoo had these great "virtual services" such that either eth0 OR eth1 could "provide net" services. This would imply that if eth0 didn't start, eth1 (wireless) would try and if either starts, then all the other dependent services (netmount, cupsd, etc.) would start.
I'm guessing from the above thread that my understanding of virtual services and "provides" is incorrect. Can someone please clarify? |
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Networking & Security
