static ip address and ifconfig

Sat Dec 29 21:42:14 UTC 2012

Well generally DHCP and static are mutually exclusive on the same interface. Also bear in mind that DHCP is more comprehensive than a simple address assignment system. In addition a static reservation is not the same thing as a static IP address assignment on an interface. They are similar but different.

A DHCP assignment will bind one address to a MAC as well as configure address resolution, routing et cettera… Whereas a static IP assignment must be configured manually by you the human and not the ISP. Your ISP can route a block of addresses to you via a CPE like a DSL modem or router but you have to configure your equipment to consume the traffic passed on by that device. 

For instance my cable provider's modem boots DHCP, as does the router that they configure via DHCP net boot so that it may receive the block of static IP addresses assigned to my account. The router itself consumes the first usable address as delivered by the ISP. I am free to assign the remain 5 addresses to any device be-it a firewall or server at my discretion and connect it to the LAN side of this router. The following is sort of what these static assignment will look like on this server.

xl1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	ether 00:17:02:d3:84:6f 
	inet 75.99.82.91 netmask 0xfffffff8 broadcast 75.99.82.95
	inet 75.99.82.93 netmask 0xfffffff8 broadcast 75.99.82.95
	inet 75.99.82.92 netmask 0xfffffff8 broadcast 75.99.82.95
	media: autoselect (100baseTX <full-duplex>)
	status: active

Regards,
Mikel King
Senior Editor, BSD News
http://bsdnews.net

On Dec 29, 2012, at 4:16 PM, Fbsd8 <fbsd8 at a1poweruser.com> wrote:

> snip previous
>> It still all depends on your configuration, it won't look any different than a static private IP address shows when doing an ifconfig except it will be the public IP.  Generally if you have a static IP you will have to set it manually, and it won't get it via DHCP.  But I have worked with some DSL connections though that assigned the static IP through a DHCP reservation based on your modem/routers MAC address.  However that would only work for a single IP.  If you get 25, you can assign those with aliases to make a single server answer on the others as well, common for servers hosting multiple https web sites.
>> Here's an example with Aliases, its from a LAN with private range, but would look no different except IPs if it was public range addresses.  This is from my web/email server (the very one this message comes from), the secondary IP is for running jails, when testing upgrades.
>> LAN: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000
>>        options=209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC>
>>        ether 00:07:e9:09:be:4f
>>        inet 192.168.5.1 netmask 0xffffff00 broadcast 192.168.5.255
>>        inet 192.168.5.21 netmask 0xffffff00 broadcast 192.168.5.255
>>        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
>>        media: Ethernet autoselect (1000baseT <full-duplex>)
>>        status: active
>> Here's an example from a public range, pulled this from my pfSense box, which is on a Cable Connection with a block of 5 static IP Addresses.
>> vr1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>>    options=8280b<RXCSUM,TXCSUM,VLAN_MTU,WOL_UCAST,WOL_MAGIC,LINKSTATE>
>>    ether 00:0d:b9:1c:78:2d
>>    inet 24.240.198.186 netmask 0xfffffff8 broadcast 24.240.198.191
>>    inet6 fe80::20d:b9ff:fe1c:782d%vr1 prefixlen 64 scopeid 0x2
>>    nd6 options=43<PERFORMNUD,ACCEPT_RTADV>
>>    media: Ethernet autoselect (100baseTX <full-duplex>)
>>    status: active
>> There's just a single IP set, though it does relay connections on other IPs, using proxy arp to do this so there is no need for an alias to be defined.
> 
> So your saying the ISP forwards any internet traffic for those static ip address to the on site "modem/router" MAC address which my service was previsioned to?
> 
> The ISP is sending DNS port 53 and DHCP port 67 traffic on each static ip address as well?
> 
> I can configure the on site modem/router to assign selected static ip address to a router's hardware port which is cabled to different PC's?
> 
> The PC's would only be seeing traffic for that selected static ip address?
> 
> The rc.config statement ifconfig_xl0="DHCP" on that PC would function as exspected?
> 
> 
> Now if I only had a on site "modem" with a single output port, then
> all the static ip address would hit the NIC card it was cabled to?
> 
> So on the single FreeBSD system with NIC xl0 being cabled to the single port coming from the on site modem I would need ifconfig statements in rc.conf to select what static ip address I want to use for DHCP to automatically get the ISP's DSN ip address?  Please correct my syntax if wrong
>    ifconfig_xl0="DHCP,24.240.xxx.186"
> 
> If I wanted to use the remaining static ip address for other PC's on my private LAN I would have to have additional ifconfig statements in rc.conf?
>    ifconfig_xl0="alias,24.240.xxx.187,24.240.xxx.188,24.240.xxx.189"
> or would I need a single statement for each alias? Please correct my syntax if wrong.
> 
> I would also have to configure my firewall to redirect those alias static ip address to the LAN ip address of the servers I want to target?
> 
> For some of the remaining static ip address i have not used yet, I would like to use them for jails. Using the jail option to provide the
> interface name to bound to which automatically creates an alias for the jails ip address at jail start time and also removes it when the jail stopped. I can do this by creating the jail using one of the unused static ip address?
> 
> 
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> 
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