Re: Cheap Gigabit switch will allow DHCP thru it?
Jeff Macdonald wrote: On Dec 29, 2007 12:31 PM, Bruce Labitt [EMAIL PROTECTED] wrote: I'm looking to add another hdhomerun tunerbox to my myth setup. I have a DHCP server running to give the existing tuner its IP address. Can I add a cheap gigabit switch to add the other tuner? Will the requests for IP address be routed to the server properly? I have a cheap netgear gigabit switch and all the devices do dhcp that are connected on it. I have found to my dismay, that I have my on board ethernet port (gigabit) connected to to my router (only 100Mbit). It is a dhcp client. My add on cheap ethernet card (100Mbit) is connected to the hdhomerun. It has the dhcp server for the hdhomerun(s). Is there a simple way to swap eth0 and eth1? I *think* this would work... I would want the 1Gbit interface to go the the switch and the hdhomeruns. It would have dhcp server. The 100Mbit interface would go to my router for the external interface. It would be a dhcp client, getting its IP from the router. I could just put in a gigabit ethernet card, but that would be $20 or so. What is my best option? TIA ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
DHCP, ARP, RARP, PXE, ICMP, OSI, TMA (was: Cheap Gigabit switch ...)
On Dec 29, 2007 3:15 PM, Paul Lussier [EMAIL PROTECTED] wrote: If memory serves (though, often times, sadly, it serves incorrectly :) DHCP is heavily dependant upon (r)ARP (specifically when combined with PXE), which kinda sorta sits in a no-where land between layers 2 and 3 (like ICMP). I think this is one of those times memory is serving you somewhat incorrectly. :) Which means that it is time for -- you guessed it -- one of my patented long messages on the details of technology! :-) == DHCP == DHCP is implemented entirely in broadcast UDP [1]. To find a DHCP server, the DHCP client sends a DHCPDISCOVER datagram to the universal broadcast address, 255.255.255.255. Every node on the local network is supposed to get that datagram. Any DHCP server will then respond with a DHCPOFFER broadcast identifying itself. The client will pick a DHCP server, and send a broadcast DHCPREQUEST identifying which server it picked. The server sees that, and broadcasts a DHCPACK. The IP layer is responsible for translating IP broadcasts into data-link layer terms. For Ethernet, it just sends a frame to the Ethernet broadcast address (FF:FF:FF:FF:FF:FF). Because it's all done using broadcasts, ARP never gets involved. [1] Exception: If the DHCP client already has an active lease, and just wants to renew it, the DHCP client and server will use unicast datagrams in that transaction. So ARP gets involved there. == ARP == Now, it is true that just about everything using IP is heavily dependent on ARP [2], because ARP is responsible for turning unicast IP addresses into unicast Ethernet addresses. An ARP failure means no IP datagrams can be sent to a given IP address, which means no TCP, UDP, ICMP, or anything else. ARP is part of the IP suite, but not layered on top of the actual Internet Protocol. It exists alongside IP. ARP is easiest to explain by example. Say we have two nodes, ALPHA and BRAVO, on an Ethernet. ALPHA has IP address 192.0.2.10, and BRAVO has IP address 192.0.2.99. ALPHA wants to send a packet to BRAVO, and knows BRAVO's IP address. But it doesn't know the Ethernet address of BRAVO. So ALPHA sends an Ethernet broadcast frame (the ARP request), saying I have IP address 192.0.2.10. Who has IP address 192.0.2.99? Everybody on that Ethernet sees the request. BRAVO recognizes its address, and responds with a unicast Ethernet frame saying, I have 192.0.2.99.. BRAVO can use unicast because it got the ALPHA's Ethernet address from the ARP request frame. [2] Exception: Not every data-link type needs ARP. It is possible to have other means of deriving data-link addresses, and point-to-point links (SLIP, PPP, etc.) don't need to. == RARP == RARP is a completely a different design vs DHCP/BOOTP. RARP has the game goal as DHCP, in that RARP exists to let nodes without an IP address discover what their IP address should be. However, RARP does not use UDP or anything else on top of, or within, the Internet Protocol itself. RARP is implemented outside of the IP layer, using data-link frames, similar to ARP. RARP is also limited to assigning an IP address, nothing more; DHCP can assign arbitrary configuration parameters. == PXE == PXE doesn't really have anything to do with DHCP directly. PXE is just a standard network boot mechanism for the i386 IBM-PC architecture. Of course, PXE does use DHCP to discover it's boot configuration, but the DHCP it uses is no different than another other DHCP (in terms of DHCP internals). I've never seen anything about PXE being able to use RARP, but then, nobody uses RARP these days, so maybe it's possible and just nobody cares. :) == ICMP == ICMP is implemented on top of the IP layer, along side the TCP and UDP layers. All ICMP datagrams are IP datagrams, same as UDP or TCP. Other than their specific payload, there is nothing different about ICMP datagrams vs other IP datagrams. == OSI model == The 7-layer OSI network model does not really equate neatly, one-to-one, with the IP model. That's why I called IP and friends layer 3 and higher. It is accurate to say that everything in the IP suite is implemented at layer 3 or higher. Layer 2, the data-link layer, would be things like Ethernet, FDDI, Token-Ring, ATM, PPP, 802.11 wireless, and so on. Everything in the IP suite, including IP itself, along with ARP and RARP, is implemented on top of the data-link layer, putting them in layer 3 or higher. IP itself does closely fit in the OSI model's idea of a layer 3 (network layer) protocol. However, ICMP would also be considered a network layer function in OSI, but it's stacked on top of IP. ARP would also be considered a OSI network layer function, but it exists outside of IP itself. UDP is strictly a layer 4 (transport) protocol by OSI terms, but TCP handles both transport and session (layer 5) functions in the OSI model. So fitting the IP suite in to the OSI model is kind of a mess. Fortunately, nobody really
Re: Cheap Gigabit switch will allow DHCP thru it?
On Dec 30, 2007 1:16 PM, Bruce Labitt [EMAIL PROTECTED] wrote: Is there a simple way to swap eth0 and eth1? You're running Fedora, right? If so, get to a root shell prompt, and do the following: service network stop cd /etc/sysconfig/network-scripts mv ifcfg-eth0 ifcfg-tmp mv ifcfg-eth1 ifcfg-eth0 mv ifcfg-tmp ifcfg-eth1 # now swap the actual network cables (don't type this line :) ) service network start Unless you've got something referencing the actual network interfaces -- which is unusual, most things use IP addresses -- this should work fine. The one question mark might be the firewall. If needed, you can reconfigure it using the command: system-config-securitylevel -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
Is there a simple way to swap eth0 and eth1?
If your system has udev you might find a file with a name
something like /etc/udev/rules.d/z25_persistent-net.rules that
has entries something like this:
SUBSYSTEM==net, DRIVERS==?*, ATTR{address}==00:12:3f:57:4a:66,
NAME=eth0
...which can force the NIC with the specified MAC addr to be
assigned the specified interface name. Just be sure that if
you arrange for an interface to get a new name you also ensure
that all config files that refer to that interface by the old
name are changed to reflect the new name.
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Re: Cheap Gigabit switch will allow DHCP thru it?
Ben Scott wrote: On Dec 30, 2007 1:16 PM, Bruce Labitt [EMAIL PROTECTED] wrote: Is there a simple way to swap eth0 and eth1? You're running Fedora, right? If so, get to a root shell prompt, and do the following: service network stop cd /etc/sysconfig/network-scripts mv ifcfg-eth0 ifcfg-tmp mv ifcfg-eth1 ifcfg-eth0 mv ifcfg-tmp ifcfg-eth1 # now swap the actual network cables (don't type this line :) ) service network start Unless you've got something referencing the actual network interfaces -- which is unusual, most things use IP addresses -- this should work fine. The one question mark might be the firewall. If needed, you can reconfigure it using the command: system-config-securitylevel You will also need to edit the ifcfg-eth0 and ifcfg-eth1 files to actually say DEVICE=eth0 and DEVICE=eth1 respectively. Since udev is on by default (at least in FC8), you will need to edit /etc/udev/... (Mike ODonnell mentioned this in another post). You may also find /etc/modules.conf needs editing. I do a grep -r eth0 /etc/* to find all the relevant places when I need to do this sort of thing. begin:vcard fn:Dan Jenkins n:Jenkins;Dan org:Rastech Inc. adr:;;21 Curtis Lane;Bedford;NH;03110;USA email;internet:[EMAIL PROTECTED] title:Technical Director tel;work:1-603-206-9951 x-mozilla-html:FALSE version:2.1 end:vcard ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
On Dec 30, 2007 2:24 PM, Dan Jenkins [EMAIL PROTECTED] wrote: You will also need to edit the ifcfg-eth0 and ifcfg-eth1 files to actually say DEVICE=eth0 and DEVICE=eth1 respectively. D'oh! You're right. I always forget that. Since udev is on by default (at least in FC8), you will need to edit /etc/udev/... Not if if you're swapping the IP configurations, as described above. In that case, the device names should stay the same. Alternatively, you can swap the device names, and keep the IP configuration untouched. Swapping both will end up doing nothing. You may also find /etc/modules.conf needs editing. Only if changing device names, and not the assigned IP configurations. I do a grep -r eth0 /etc/* to find all the relevant places when I need to do this sort of thing. That's a good idea. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
Ben Scott wrote: On Dec 30, 2007 2:24 PM, Dan Jenkins [EMAIL PROTECTED] wrote: You will also need to edit the ifcfg-eth0 and ifcfg-eth1 files to actually say DEVICE=eth0 and DEVICE=eth1 respectively. D'oh! You're right. I always forget that. As have I, which is why I remember it now. Since udev is on by default (at least in FC8), you will need to edit /etc/udev/... Not if if you're swapping the IP configurations, as described above. In that case, the device names should stay the same. Alternatively, you can swap the device names, and keep the IP configuration untouched. Swapping both will end up doing nothing You may also find /etc/modules.conf needs editing. Only if changing device names, and not the assigned IP configurations. Good point. I had forgotten the original reason. (Not good when answering questions.) I'm usually swapping them from another reason. begin:vcard fn:Dan Jenkins n:Jenkins;Dan org:Rastech Inc. adr:;;21 Curtis Lane;Bedford;NH;03110;USA email;internet:[EMAIL PROTECTED] title:Technical Director tel;work:1-603-206-9951 x-mozilla-html:FALSE version:2.1 end:vcard ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
On Sunday 30 December 2007 01:49:39 pm Ben Scott wrote: On Dec 30, 2007 1:16 PM, Bruce Labitt [EMAIL PROTECTED] wrote: Is there a simple way to swap eth0 and eth1? You're running Fedora, right? If so, get to a root shell prompt, and do the following: service network stop cd /etc/sysconfig/network-scripts mv ifcfg-eth0 ifcfg-tmp mv ifcfg-eth1 ifcfg-eth0 mv ifcfg-tmp ifcfg-eth1 # now swap the actual network cables (don't type this line :) ) service network start You also need to change the DEVICE= line in ifcfg-eth0 and ifcfg-eth1 to match, and for good measure, should update /etc/modprobe.conf as well to alias the right module to the device. -- Jarod Wilson [EMAIL PROTECTED] ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
On Dec 30, 2007 7:15 PM, Jarod Wilson [EMAIL PROTECTED] wrote: You also need to change the DEVICE= line in ifcfg-eth0 and ifcfg-eth1 to match, and for good measure, should update /etc/modprobe.conf as well to alias the right module to the device. You won't need to modify /etc/modprobe.conf if you're only swapping IP configurations between logical devices. And swapping both will cancel-out the config changes. Bruce currently has something like the following: SOHO router = onboard, named eth0, configured as 192.168.1.0/24, default gateway HDHomeRun = card, named eth1, configured as 10.0.0.0/24 He wants swap the devices connected to the NICs. That's a physical change, and is the whole point of this. :) So after the cable swap, we have this: HDHomeRun = onboard, named eth0, configured as 192.168.1.0/24, default gateway SOHO router = card, named eth1, configured as 10.0.0.0/24 Now the problem is, his system will still be trying to talk to the Internet using the cable that's plugged into his tuner, and MythTV will be trying to find the tuner where the router is. That won't work at all. My suggestion (modulo the forgotten config edit) is swap the configuration being applied to the logical device names. The result would be: HDHomeRun = onboard, named eth0, configured as 10.0.0.0/24 SOHO router = card, named eth1, configured as 192.168.1.0/24, default gateway The other approach, originally suggested by MOD, would be to swap the names the kernel is assigning to the devices: SOHO router = onboard, named eth1, configured as 192.168.1.0/24, default gateway HDHomeRun = card, named eth0, configured as 10.0.0.0/24 Thinking about it, I actually like the later method better, as it bypasses any firewall/DHCP/etc config file changes to update devices. You just change what each device is being called. -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Cheap Gigabit switch will allow DHCP thru it?
On Sunday 30 December 2007 07:50:55 pm Ben Scott wrote: On Dec 30, 2007 7:15 PM, Jarod Wilson [EMAIL PROTECTED] wrote: You also need to change the DEVICE= line in ifcfg-eth0 and ifcfg-eth1 to match, and for good measure, should update /etc/modprobe.conf as well to alias the right module to the device. You won't need to modify /etc/modprobe.conf if you're only swapping IP configurations between logical devices. And swapping both will cancel-out the config changes. If only swapping IP configs, sure. If also changing devices, still not actually necessary, as the network bring-up scripts actually handle renaming devices as needed to match the ifcfg-ethX files, but still recommended for consistency. -- Jarod Wilson [EMAIL PROTECTED] ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
Re: Photo gallery sw with tagging?
Paul Lussier writes: At one time I used PHP Gallery for my photo album. I haven't done anything in this area in a while, and was wondering what else was out there people were using. I'd ideally like something which allowed me to tag photos with random strings so I can then search/sort based on those tags. This is for home use, so I don't really want a service like Flickr, etc. You might like digiKam. Regards, --kevin -- GnuPG ID: B280F24E God, I loved that Pontiac. alumni.unh.edu!kdc -- Tom Waits ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
