quite handy. For instance, they can be used for IP based hosting (think
webservers), failover of clustered services, testing, providing network
connectivity for zones, etc. Additionally, they are relatively trivial
to setup and use (see note 1). As an aside, in the details below, the
terms logints and vips are used interchangeably. The following details
these interfaces for each of our three hosts:
HOSTS: beastie, snorkle, tux PROMPT: host [0] OS: FreeBSD 8.1 (beastie) Solaris 10 (snorkle) CentOS 5.4 Linux (tux)For point of examples, FreeBSD (bsd) is used, however, both Solaris
(sol) and CentOS (lin) follow at the end. Let's start with listing
our available interfaces to identify which will be configured for a vip
(step 1, sol|lin):
beastie [0] /sbin/ifconfig -a em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM> ether 08:00:27:ce:11:c0 inet 10.0.23.181 netmask 0xfffffe00 broadcast 10.0.23.255 media: Ethernet autoselect (1000baseT <full-duplex>) status: active em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM> ether 08:00:27:d2:4e:8b <snip...>From the above, I want to configure a vip on em0 with the next available
IP address (step 2, sol|lin):
beastie [0] /sbin/ifconfig em0 alias 10.0.23.182 netmask 255.255.254.0 up beastie [0] /sbin/ifconfig em0 em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM> ether 08:00:27:ce:11:c0 inet 10.0.23.181 netmask 0xfffffe00 broadcast 10.0.23.255 inet 10.0.23.182 netmask 0xfffffe00 broadcast 10.0.23.255 media: Ethernet autoselect (1000baseT <full-duplex>) status: activeWe now have em0 configured to respond to two separate IP addresses.
Now, to retain the configuration for bootup (step 3, sol|lin):
# edit /etc/rc.conf adding either of the following (see note 2):
ipv4_addrs_em0="10.0.23.182/23" or ifconfig_em0_alias0="inet 10.0.23.182 netmask 0xfffffe00"# the following is the result (using ipv4_addrs_em0):
beastie [127] /bin/cat /etc/rc.conf # -- sysinstall generated deltas -- # Thu Sep 23 19:40:11 2010 # Created: Thu Sep 23 19:40:11 2010 # Enable network daemons for user convenience. # Please make all changes to this file, not to /etc/defaults/rc.conf. # This file now contains just the overrides from /etc/defaults/rc.conf. defaultrouter="127.0.0.1" hostname="beastie" ifconfig_em0="inet 10.0.23.181 netmask 255.255.254.0" ipv4_addrs_em0="10.0.23.182/23" ifconfig_em1="inet 192.168.56.35 netmask 255.255.255.0" inetd_enable="YES" sshd_enable="YES" sendmail_enable="NO" sendmail_submit_enable="NO"At this point, the logint has been created and is available for use.
If desired, an entry could be added to /etc/hosts. If the logint /
vip is no longer necessary, delete its alias entry from /etc/rc.conf
and execute the following (step 4, sol|lin):
beastie [0] /sbin/ifconfig em0 -alias 10.0.23.182 netmask 255.255.254.0 beastie [0] /sbin/ifconfig em0 em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM> ether 08:00:27:ce:11:c0 inet 10.0.23.181 netmask 0xfffffe00 broadcast 10.0.23.255 media: Ethernet autoselect (1000baseT <full-duplex>) status: active
Solaris:
step 1 (bsd|lin):
snorkle [0] /sbin/ifconfig -a lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 e1000g0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3 inet 10.0.23.191 netmask ffffff00 broadcast 10.0.23.255 ether 8:0:27:56:c2:d e1000g1: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2 inet 192.168.56.15 netmask ffffff00 broadcast 192.168.56.255 ether 8:0:27:cb:f8:20step 2 (bsd|lin), Solaris adds a visible logical interface to the physical
interface identified by e1000g0. Solaris also provides two separate
command invocations, depending on your intention (note 3):
snorkle [0] /sbin/ifconfig e1000g0 addif 10.0.23.192 netmask 255.255.254.0 broadcast + up Created new logical interface e1000g0:1 or snorkle [0] /sbin/ifconfig e1000g0:3 plumb snorkle [0] /sbin/ifconfig e1000g0:3 10.0.23.194 netmask 255.255.254.0 broadcast + up snorkle [0] /sbin/ifconfig -a lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 e1000g0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3 inet 10.0.23.191 netmask ffffff00 broadcast 10.0.23.255 ether 8:0:27:56:c2:d e1000g0:1: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3 inet 10.0.23.192 netmask fffffe00 broadcast 10.0.23.255 e1000g0:3: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3 inet 10.0.23.194 netmask fffffe00 broadcast 10.0.23.255step 3 (bsd|lin), create and configure the interface file:
snorkle [0] /usr/bin/vi /etc/hostname.e1000g0:1 snorkle [0] /usr/bin/cat /etc/hostname.e1000g0:1 10.0.23.192 netmask 255.255.255.0 broadcast +step 4 (bsd|lin), remove the logint. Again, Solaris provide two ways (note 3):
snorkle [0] /sbin/ifconfig e1000g0:3 unplumb or snorkle [0] /sbin/ifconfig e1000g0 removeif 10.0.23.192 snorkle [0] /sbin/ifconfig -a lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 e1000g0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3 inet 10.0.23.191 netmask ffffff00 broadcast 10.0.23.255 ether 8:0:27:56:c2:d e1000g1: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2 inet 192.168.56.15 netmask ffffff00 broadcast 192.168.56.255 ether 8:0:27:cb:f8:20
Linux:
step 1 (bsd|sol):
tux [0] /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8 inet addr:10.0.23.171 Bcast:10.0.23.255 Mask:255.255.254.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Interrupt:169 Base address:0xd020 eth1 Link encap:Ethernet HWaddr 08:00:27:53:7B:56 inet addr:192.168.56.25 Bcast:192.168.56.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:869 errors:0 dropped:0 overruns:0 frame:0 <snip...>step 2 (bsd|sol):
tux [0] /sbin/ifconfig eth0:1 10.0.23.172 netmask 255.255.254.0 up tux [0] /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8 inet addr:10.0.23.171 Bcast:10.0.23.255 Mask:255.255.254.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Interrupt:169 Base address:0xd020 eth0:1 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8 inet addr:10.0.23.172 Bcast:10.0.23.255 Mask:255.255.254.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Interrupt:169 Base address:0xd020 eth1 Link encap:Ethernet HWaddr 08:00:27:53:7B:56 <snip...>step 3 (bsd|sol), create and configure the interface file (note 4):
tux [0] /usr/bin/cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:1 tux [0] /bin/vi /etc/sysconfig/network-scripts/ifcfg-eth0:1 tux [0] /bin/cat /etc/sysconfig/network-scripts/ifcfg-eth0:1 # Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE] DEVICE=eth0:1 BOOTPROTO=static BROADCAST=10.0.23.255 HWADDR=08:00:27:9e:a8:a8 IPADDR=10.0.23.172 NETMASK=255.255.254.0 NETWORK=10.0.22.0 ONBOOT=yesstep 4 (bsd|sol):
tux [0] /sbin/ip address delete 10.0.23.172/23 dev eth0:1 tux [0] /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8 inet addr:10.0.23.171 Bcast:10.0.23.255 Mask:255.255.254.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:6 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:252 (252.0 b) Interrupt:169 Base address:0xd020 eth1 Link encap:Ethernet HWaddr 08:00:27:53:7B:56 inet addr:192.168.56.25 Bcast:192.168.56.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1923 errors:0 dropped:0 overruns:0 frame:0 <snip...>
NOTES
note 1: Any logints / vips created will have the same HWaddr (MAC addr)
as the underlying physical interface. Also, they will share the
capacity of the network link. If you have something that requires
unique HWaddrs or can possibly saturate the link, vips may not be
the way to go. Also, though the above shows vips configured in the
same network as the underlying physical interface, you can actually
configure other networks instead. Your network architecture must
support this, however.
note 2: According to the rc.conf man page, 'ipv4_addrs_int#' is favored
over 'ifconfig_int#_alias#'. The reason for this is if you have
aliases 1 - 4 and 6, alias6 will never be added since the init script
is looking for the next in line which would be alias5. Additionally,
it appears that there isn't a correlative for 'ipv6_addrs_int#', so
'ifconfig_int#_alias#' would need to be used. Providing that you
understand that risk, either method could be used, at least for IPv4.
The following illustrates multiple vips for em0 using each declaration
statement:
ipv4_addrs_em0="10.0.23.182/23 10.0.23.183/23" or ifconfig_em0_alias0="inet 10.0.23.182 netmask 0xfffffe00" ifconfig_em0_alias1="inet 10.0.23.183 netmask 0xfffffe00"note 3: Solaris provides two command syntaxes for for logints.
The first, using 'addif' to 'ifconfig' creates a new logical interface
at the next available logical instance number. The second, using
'plumb' to 'ifconfig' allows you to set the specific logical instance
to create. For removal, 'removeif' removes the specific logical
interface identified by the IP address in question. As with 'plumb',
'unplumb' removes the specified logical instance by instance name.
note 4: Linux has a nasty little habit of always trying to respond,
including to things perhaps not within the same network segment.
It will also respond to arp via the physical interface and the
logical interfaces created rather than just picking one. If this
is an issue, have a look at the 'net.ipv4.conf.default.arp_announce'
and 'net.ipv4.conf.default.arp_ignore' 'sysct.conf' variables.
