On Wed, 14 Jul 2004 23:06:38 -0400 epilogue <[EMAIL PROTECTED]> wrote:
> On Wed, 14 Jul 2004 16:40:10 -0600 > Danny MacMillan <[EMAIL PROTECTED]> wrote: > > > On Wed, Jul 14, 2004 at 03:41:04AM -0600, Matthew Seaman wrote: > > > On Tue, Jul 13, 2004 at 02:32:46PM -0700, Darren Pilgrim wrote: > > > > > > > > ifconfig_ed0="inet 192.168.1.0/24 netmask 255.255.0.0" > > > > > ifconfig_vr0="inet 192.168.0.0/24 netmask 255.255.0.0" > > > > > > > > 192.168.1.0/24 and 192.168.0.0/24 are blocks of addresses in CIDR > > > > notation, not the actual addresses to be fed to ifconfig. You need > > > > to pick addresses within the netblock to use for myserver and all > > > > the other machines on your network. Since myserver can reach the > > > > internet just fine, you should keep the IP address for vr0 the > > > > same, just lengthen the netmask to allow the use of 192.168.1.0/24 > > > > on the LAN. > > > > > > ifconfig(8) understands CIDR notation just fine, although it's not > > > usual to configure an interface using the '.0' /network/ address. > > > Look on it as a third alternate way of specifying the netmask, so > > > that the following three examples are equivalent: > > > > > > ifconfig fxp0 inet 192.168.123.74/29 > > > ifconfig fxp0 inet 192.168.123.74 netmask 0xfffffff8 > > > ifconfig fxp0 inet 192.168.123.74 netmask 255.255.255.248 > > > > > > Those correspond to the slightly contrived example of the /29 network > > > starting with network address 192.168.123.72 and running up to the > > > broadcast address 192.168.123.79 > > > > > > Note: you can give a broadcast address on the ifconfig command line, > > > but usually it's not necessary as a standard value will be calculated > > > from any ip number forming part of that network and from the netmask. > > > However you can't in general use ip address + broadcast to do the > > > converse, as there isn't necessarily a unique solution. > > > > I apologize for asking this question here, but I've googled and read > > arp(4) and arp(1) and nothing I can see gives a clear answer (at least > > clear to me). It is related to this thread. > > > > Is it the subnet mask that lets my computer know that for an IP address > > located external to my network it should send the packet to the router > > (using the router's MAC address) instead of arp-ing for the MAC address > > of the target node? > > hello danny, > > i'm only going to speak to the part immediately above... > > kind of yes, but mostly no. er, how about we forget that i said 'kind of yes, but mostly no' and go with 'yes, for machines off your network'? i don't know how that slipped in there. ;) > the subnet mask simply provides a mathematical > means to segment a single ip block into smaller separate networks. > technically, the computer will look at it's local network (defined by the > block and subnet mask) to determine if the target machine is local. if > not, your machine knows the target machine must be on another network and > it forwards the packets to the only other place it can, whatever gateway > you've defined (ie. your local router), which then forwards it up the > point-to-point connection to its gateway (your ISP's router), which > continues to forward it based on IP... > > afaik, MAC addresses have nothing to do with this directly. yes, MAC > addresses (OSI model - data link - layer 2) are mapped to IP addresses > (OSI model - network - layer 3) and vice versa. these are kept in a > cache in order to speed up routing, somewhat like having a DNS cache can > avoid much of the processing wasted on resolving frequently used > addresses. generally speaking, this cache is volatile in nature and can > be cleared manually or by power-cycling a router, to provide two > examples. > > In case you're curious, this doc is a good primer on IP Addressing and > subnetting. > > "Understanding IP Addressing: Everything You Ever Wanted To Know" > http://www.3com.com/other/pdfs/infra/corpinfo/en_US/501302.pdf > > for more about the ISO model, see google. sorry i don't have an > interesting link handy. > > hoping that this answered at least part of your question, and crossing > my fingers that i didn't muddle up any of these details (it has been a > while since i've looked at this). > > > cheers, > epi > > > > This is the only way I can see that this would > > make sense, as arp -a doesn't seem to return the MAC addresses of boxes > > on the other side of my router under any circumstances. I read a > > document online that suggested that a router would recursively ARP for > > a non-local MAC address but this seems insane and highly improbable to > > me. More likely is that my computer, knowing that an IP address is > > not local by examining the network address, would choose a route from > > its routing table, arp for that router's MAC address, and send the > > packet thither. But is that what actually happens? > > > > Pointers to documentation explaining this accepted with my thanks. > > > > -- > > Danny MacMillan > > > > _______________________________________________ > > [EMAIL PROTECTED] mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > > To unsubscribe, send any mail to > > "[EMAIL PROTECTED]" > > > _______________________________________________ > [EMAIL PROTECTED] mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "[EMAIL PROTECTED]" > _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
