/etc.
Typically, these settings are initially configured during the
installation process.
fxp0 at pci0 dev 10 function 0 "Intel 82557" rev 0x0c: irq 5, address 00:02:b3:2b:10:f7 inphy0 at fxp0 phy 1: i82555 10/100 media interface, rev. 4This device uses the fxp(4) driver and is assigned the number 0 here.
You can find out what network interfaces have been identified by using the ifconfig(8) utility. The following command will show all network interfaces on a system.
$ ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33200
index 3 priority 0 llprio 3
groups: lo
inet 127.0.0.1 netmask 0xff000000
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
lladdr 00:02:b3:2b:10:f7
index 1 priority 0 llprio 3
media: Ethernet autoselect (100baseTX full-duplex)
status: active
inet 10.0.0.38 netmask 0xffffff00 broadcast 10.0.0.255
enc0: flags=0<>
index 2 priority 0 llprio 3
groups: enc
status: active
pflog0: flags=141<UP,RUNNING,PROMISC> mtu 33200
index 4 priority 0 llprio 3
groups: pflog
This sample shows only one physical Ethernet interface: fxp0.
An IP is configured on it, hence the values
inet 10.0.0.38 netmask 0xffffff00 broadcast 10.0.0.255.
The UP and RUNNING flags are also set on it.
The netstart(8) script configures
network interfaces at boot time using
hostname.if(5) files, where
"if" is replaced by the full name of each interface.
The example above would use the file /etc/hostname.fxp0, containing
the following options:
inet 10.0.0.38 255.255.255.0This
hostname.fxp0 file also has an interactive equivalent:
# ifconfig fxp0 10.0.0.38 255.255.255.0Finally, you will notice several other interfaces come enabled by default. These are virtual interfaces that serve various functions. The following manual pages describe them:
create
subcommand.
/etc/myname and /etc/mygate files are read by the
netstart(8) script.
Both of these files consist of a single line, specifying the fully qualified
domain name of the system and the address of the gateway host, respectively.
The /etc/mygate file need not exist on all systems.
See myname(5) for more details.
$ cat /etc/resolv.conf search example.com nameserver 125.2.3.4 nameserver 125.2.3.5 lookup file bindHere, the default domain name will be
example.com,
there will be two DNS resolvers,
125.2.3.4 and 125.2.3.5, and the
hosts(5) file will be consulted
before the DNS resolvers are.
# sh /etc/netstartNote that a few warnings may be produced when running this script if you are reconfiguring interfaces that have already been configured. Use ifconfig(8) to make sure that your interfaces were set up correctly.
Even though you can completely reconfigure networking on a running OpenBSD system, a reboot is recommended after any significant reconfiguration.
$ netstat -rn Routing tables Internet: Destination Gateway Flags Refs Use Mtu Prio Iface default 10.0.0.1 UGS 4 16 - 12 fxp0 224/4 127.0.0.1 URS 0 0 32768 8 lo0 127/8 127.0.0.1 UGRS 0 0 32768 8 lo0 127.0.0.1 127.0.0.1 UH 2 15 32768 1 lo0 10.0.0/24 link#1 UC 1 4 - 4 fxp0 10.0.0.1 aa:0:4:0:81:d UHL 1 11 - 1 fxp0 10.0.0.38 127.0.0.1 UGHS 0 0 - 1 lo0 $ route show Routing tables Internet: Destination Gateway Flags Refs Use Mtu Prio Iface default 10.0.0.1 UGS 4 16 - 12 fxp0 base-address.mcast localhost URS 0 0 32768 8 lo0 loopback localhost UGRS 0 0 32768 8 lo0 localhost localhost UH 2 15 32768 1 lo0 10.0.0/24 link#1 UC 1 4 - 4 fxp0 10.0.0.1 aa:0:4:0:81:d UHL 1 11 - 1 fxp0 10.0.0.38 localhost UGHS 0 0 - 1 lo0
Suppose you have a dc0 interface.
You are on the network 192.168.0.0,
the IP address for dc0 is
192.168.0.2 and the netmask is 255.255.255.0.
Assuming you are using multiple IP addresses which are in the same subnet
with aliases, your netmask setting for each alias becomes
255.255.255.255.
They do not need to follow the netmask of the first IP bound to the interface.
In this example,
two aliases are added to the interface dc0, which was configured as
192.168.0.2 with a netmask of 255.255.255.0.
$ cat /etc/hostname.dc0 inet 192.168.0.2 255.255.255.0 inet alias 192.168.0.3 255.255.255.255 inet alias 192.168.0.4 255.255.255.255Once you've created this file, run netstart or reboot. To view all aliases, use
ifconfig -A.
dhcpOpenBSD will gather its IP address, default gateway and DNS servers from the DHCP server at startup time.
If you want to get an IP via DHCP from the command line, simply run:
# dhclient xl0Replace
xl0 with your interface name.
The resolv.conf file will be overwritten by
dhclient(8) if the DHCP
server provides the domain-name, domain-search or domain-name-servers
options.
Any of these can be ignored, overridden or modified with appropriate
statements in
dhclient.conf(5).
For example, if you wanted to use the DNS server at 1.2.3.4 rather than
the one(s) the DHCP server provided, add the following:
supersede domain-name-servers 1.2.3.4;Additionally, the file
/etc/resolv.conf.tail can be used to
append information if dhclient(8)
does write resolv.conf.
# rcctl enable dhcpdOn the next boot, dhcpd will run and attach to all NICs that have valid configurations in dhcpd.conf(5). You may specify individual interfaces instead by naming them explicitly.
# rcctl set dhcpd flags em1 em2An example
/etc/dhcpd.conf file might look like this:
# Home
subnet 192.168.1.0 netmask 255.255.255.0 {
option domain-name-servers 192.168.1.2;
option routers 192.168.1.1;
range 192.168.1.3 192.168.1.50;
}
# Guests
subnet 172.16.0.0 netmask 255.255.255.0 {
option domain-name-servers 209.244.0.3, 8.8.8.8;
option routers 172.16.0.1;
range 172.16.0.2 172.16.0.254;
}
There are two subnets in this example: a home network and a guest network.
Clients will automatically be given an IP address and pointed to the gateway
and DNS servers you specify.
See dhcp-options(5) for more
options.
The following cards support Host-based Access Point (HostAP) mode, permitting them to be used as a wireless access point:
media subcommand shows media capabilities of network interfaces.
For wireless devices, it displays supported 802.11a/b/g/n media modes and the
supported operating modes (hostap, ibss,
monitor).
For example, to see media capabilities of interface ath0, type:
$ ifconfig ath0 mediaIn order to use some wireless cards, you will need to acquire firmware files with fw_update(1). Some manufacturers refuse to allow free distribution of their firmware, so it can't be included with OpenBSD.
Another option to consider: use a conventional NIC and an external bridging wireless access point for your OpenBSD-based firewall. This has the added advantage of letting you easily position the antenna where it is most effective, which is often not directly on the back of your firewall.
An example of a hostname.if(5) file for a wireless client might be:
nwid puffyuberalles wpakey passwordhere dhcpOr, for multiple access points:
join home-net wpakey passwordhere join work-net wpakey passwordhere join cafe-wifi dhcpNote that the
dhcp keyword should be after the other configuration
lines, as the network adapter will not be able to send a DHCP request until
it is configured.
To do this, we first activate the two physical ports, then assign them to
trunk0.
# echo up > /etc/hostname.bge0The wireless interface, however, needs a bit more configuration. It will need to attach to our wireless WPA-protected network:
$ cat /etc/hostname.iwn0 nwid puffynet wpakey mysecretkey upNow, our trunk interface is defined like this:
$ cat /etc/hostname.trunk0 trunkproto failover trunkport bge0 trunkport iwn0 dhcpThe trunk is set up in
failover mode,
so either interface can be used.
If both are available, it will prefer the bge0 port,
since that is the first one added to the trunk device.
vr0 through vr3.
We want to bridge vr1, vr2 and vr3
together, leaving out vr0 for the uplink.
We also want to serve IP addresses through DHCP over the bridged interfaces.
Being a DHCP server and an uplink router, the box needs to have an IP address
on the bridged network.
It is not possible to assign an IP address directly to a bridge interface. The IP address should be added to one of the member interfaces, but we cannot use a physical interface as the link might be down, in which case the address would not be reachable. Fortunately, there is the vether(4) (virtual Ethernet) driver that can be used for this purpose. We will add it to the bridge, assign the IP address to it and make dhcpd(8) listen there.
vr1, vr2 and vr3
interfaces as up:
# echo up > /etc/hostname.vr1 # echo up > /etc/hostname.vr2 # echo up > /etc/hostname.vr3Then create the
vether0 configuration:
# echo 'inet 192.168.1.1 255.255.255.0 192.168.1.255' > /etc/hostname.vether0Configure the bridge interface to contain all the above interfaces:
$ cat /etc/hostname.bridge0 add vether0 add vr1 add vr2 add vr3 upAnd finally we make the DHCP daemon listen on the
vether0
interface:
# rcctl set dhcpd flags vether0Reboot, and voilà!
blocknonip option of
ifconfig(8) or in
hostname.bridge0,
you can prevent non-IP traffic (such as IPX or NETBEUI) from slipping
around your filters.
This may be important in some situations, but you should be aware that
bridges work for all kinds of traffic, not just IP.
0.0.0.0/0.
When the kernel is doing a route lookup to determine where to send packets
destined to that network, it can choose from any of the equal-cost routes.
In most scenarios, multipath routing is used to provide redundant uplink
connections, e.g., redundant connections to the internet.
The route(8) command is used to
add/change/delete routes in the routing table.
The -mpath argument is used when adding multipath routes.
# route add -mpath default 10.130.128.1 # route add -mpath default 10.132.0.1Verify the routes:
# netstat -rnf inet | grep default default 10.130.128.1 UGS 2 134 - fxp1 default 10.132.0.1 UGS 0 172 - fxp2In this example we can see that one default route points to
10.130.128.1, which is accessible via the fxp1
interface, and the other points to 10.132.0.1, which is accessible
via fxp2.
Since the mygate(5) file does not
yet support multipath default routes, the above commands should be added to the
bottom of the hostname.if(5)
files for the fxp1 and fxp2 interfaces.
The /etc/mygate file should then be deleted.
$ tail -1 /etc/hostname.fxp1 !route add -mpath default 10.130.128.1 $ tail -1 /etc/hostname.fxp2 !route add -mpath default 10.132.0.1Lastly, don't forget to activate the use of multipath routes by enabling the proper sysctl(8) variable.
# sysctl net.inet.ip.multipath=1 # sysctl net.inet6.ip6.multipath=1Be sure to edit sysctl.conf(5) to make the changes permanent.
Now try a traceroute to different destinations. The kernel will load balance the traffic over each multipath route.
# traceroute -n 154.11.0.4 traceroute to 154.11.0.4 (154.11.0.4), 64 hops max, 60 byte packets 1 10.130.128.1 19.337 ms 18.194 ms 18.849 ms 2 154.11.95.170 17.642 ms 18.176 ms 17.731 ms 3 154.11.5.33 110.486 ms 19.478 ms 100.949 ms 4 154.11.0.4 32.772 ms 33.534 ms 32.835 ms # traceroute -n 154.11.0.5 traceroute to 154.11.0.5 (154.11.0.5), 64 hops max, 60 byte packets 1 10.132.0.1 14.175 ms 14.503 ms 14.58 ms 2 154.11.95.38 13.664 ms 13.962 ms 13.445 ms 3 208.38.16.151 13.964 ms 13.347 ms 13.788 ms 4 154.11.0.5 30.177 ms 30.95 ms 30.593 msFor more information about how the route is chosen, please refer to RFC2992, "Analysis of an Equal-Cost Multi-Path Algorithm".
It's worth noting that if an interface used by a multipath route goes down (i.e., loses carrier), the kernel will still try to forward packets using the route that points to that interface. This traffic will of course be blackholed and end up going nowhere. It's highly recommended to use ifstated(8) to check for unavailable interfaces and adjust the routing table accordingly.
This section will go through the steps for a simple NFS setup. The example details a server on a LAN, with clients accessing NFS on the LAN. It does not cover securing NFS. We presume you have already set up packet filtering or other firewalling protection to prevent outside access.
# rcctl enable portmap mountd nfsdThen configure the list of filesystems that will be made available.
In this example, we have a server with IP address 10.0.0.1.
This server will be serving NFS only to clients within its own subnet.
This is configured in the following
exports(5) file:
$ cat /etc/exports /docs -alldirs -ro -network=10.0.0 -mask=255.255.255.0The local filesystem
/docs will be made available via NFS.
The -alldirs option specifies that clients will be able to mount at
any point under /docs as well as /docs itself.
The -ro option specifies that clients will only be granted
read-only access.
The last two arguments specify that only clients within the
10.0.0.0
network using a netmask of 255.255.255.0
will be authorized to mount this filesystem.
Now you can start the server services.
# rcctl start portmap mountd nfsdIf you make changes to
/etc/exports while NFS is already running,
you need to make mountd aware of this:
# rcctl reload mountd
To mount the /docs filesystem on host 10.0.0.1
to local filesystem /mnt, run:
# mount -t nfs 10.0.0.1:/docs /mntTo have that filesystem mounted at boot, append a line to your fstab(5):
# echo '10.0.0.1:/docs /mnt nfs ro,nodev,nosuid 0 0' >> /etc/fstabIt is important that you use
0 0 at the end of this line so that
your computer does not try to fsck(8)
the NFS filesystem on boot.
When accessing an NFS mount as the root user, the server automatically maps
root's access to username nobody and group nobody.
This is important to know when considering file permissions.
For example, take a file with these permissions:
-rw------- 1 root wheel 0 Dec 31 03:00 _daily.B20143If this file was on an NFS share and the root user tried to access this file from the NFS client, access would be denied.
The user and group that root are mapped to are configurable via the exports(5) file on the NFS server.
$ rpcinfo -p 10.0.0.1
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100005 1 udp 633 mountd
100005 3 udp 633 mountd
100005 1 tcp 916 mountd
100005 3 tcp 916 mountd
100003 2 udp 2049 nfs
100003 3 udp 2049 nfs
100003 2 tcp 2049 nfs
100003 3 tcp 2049 nfs
There are a few utilities that allow you to see what is happening with NFS.
showmount(8) allows you to view
what is currently mounted by whom.
There is also nfsstat(1), which
shows much more verbose statistics.