Documentation/networking/vrf.txt

   1 Virtual Routing and Forwarding (VRF)
   2 ====================================
   3 The VRF device combined with ip rules provides the ability to create virtual
   4 routing and forwarding domains (aka VRFs, VRF-lite to be specific) in the
   5 Linux network stack. One use case is the multi-tenancy problem where each
   6 tenant has their own unique routing tables and in the very least need
   7 different default gateways.
   8
   9 Processes can be "VRF aware" by binding a socket to the VRF device. Packets
  10 through the socket then use the routing table associated with the VRF
  11 device. An important feature of the VRF device implementation is that it
  12 impacts only Layer 3 and above so L2 tools (e.g., LLDP) are not affected
  13 (ie., they do not need to be run in each VRF). The design also allows
  14 the use of higher priority ip rules (Policy Based Routing, PBR) to take
  15 precedence over the VRF device rules directing specific traffic as desired.
  16
  17 In addition, VRF devices allow VRFs to be nested within namespaces. For
  18 example network namespaces provide separation of network interfaces at L1
  19 (Layer 1 separation), VLANs on the interfaces within a namespace provide
  20 L2 separation and then VRF devices provide L3 separation.
  21
  22 Design
  23 ------
  24 A VRF device is created with an associated route table. Network interfaces
  25 are then enslaved to a VRF device:
  26
  27          +-----------------------------+
  28          |           vrf-blue          |  ===> route table 10
  29          +-----------------------------+
  30             |        |            |
  31          +------+ +------+     +-------------+
  32          | eth1 | | eth2 | ... |    bond1    |
  33          +------+ +------+     +-------------+
  34                                   |       |
  35                               +------+ +------+
  36                               | eth8 | | eth9 |
  37                               +------+ +------+
  38
  39 Packets received on an enslaved device and are switched to the VRF device
  40 using an rx_handler which gives the impression that packets flow through
  41 the VRF device. Similarly on egress routing rules are used to send packets
  42 to the VRF device driver before getting sent out the actual interface. This
  43 allows tcpdump on a VRF device to capture all packets into and out of the
  44 VRF as a whole.[1] Similarly, netfilter [2] and tc rules can be applied
  45 using the VRF device to specify rules that apply to the VRF domain as a whole.
  46
  47 [1] Packets in the forwarded state do not flow through the device, so those
  48     packets are not seen by tcpdump. Will revisit this limitation in a
  49     future release.
  50
  51 [2] Iptables on ingress is limited to NF_INET_PRE_ROUTING only with skb->dev
  52     set to real ingress device and egress is limited to NF_INET_POST_ROUTING.
  53     Will revisit this limitation in a future release.
  54
  55
  56 Setup
  57 -----
  58 1. VRF device is created with an association to a FIB table.
  59    e.g, ip link add vrf-blue type vrf table 10
  60         ip link set dev vrf-blue up
  61
  62 2. Rules are added that send lookups to the associated FIB table when the
  63    iif or oif is the VRF device. e.g.,
  64        ip ru add oif vrf-blue table 10
  65        ip ru add iif vrf-blue table 10
  66
  67    Set the default route for the table (and hence default route for the VRF).
  68    e.g, ip route add table 10 prohibit default
  69
  70 3. Enslave L3 interfaces to a VRF device.
  71    e.g,  ip link set dev eth1 master vrf-blue
  72
  73    Local and connected routes for enslaved devices are automatically moved to
  74    the table associated with VRF device. Any additional routes depending on
  75    the enslaved device will need to be reinserted following the enslavement.
  76
  77 4. Additional VRF routes are added to associated table.
  78    e.g., ip route add table 10 ...
  79
  80
  81 Applications
  82 ------------
  83 Applications that are to work within a VRF need to bind their socket to the
  84 VRF device:
  85
  86     setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, dev, strlen(dev)+1);
  87
  88 or to specify the output device using cmsg and IP_PKTINFO.
  89
  90
  91 Limitations
  92 -----------
  93 Index of original ingress interface is not available via cmsg. Will address
  94 soon.
  95
  96 ################################################################################
  97
  98 Using iproute2 for VRFs
  99 =======================
 100 VRF devices do *not* have to start with 'vrf-'. That is a convention used here
 101 for emphasis of the device type, similar to use of 'br' in bridge names.
 102
 103 1. Create a VRF
 104
 105    To instantiate a VRF device and associate it with a table:
 106        $ ip link add dev NAME type vrf table ID
 107
 108    Remember to add the ip rules as well:
 109        $ ip ru add oif NAME table 10
 110        $ ip ru add iif NAME table 10
 111        $ ip -6 ru add oif NAME table 10
 112        $ ip -6 ru add iif NAME table 10
 113
 114    Without the rules route lookups are not directed to the table.
 115
 116    For example:
 117    $ ip link add dev vrf-blue type vrf table 10
 118    $ ip ru add pref 200 oif vrf-blue table 10
 119    $ ip ru add pref 200 iif vrf-blue table 10
 120    $ ip -6 ru add pref 200 oif vrf-blue table 10
 121    $ ip -6 ru add pref 200 iif vrf-blue table 10
 122
 123
 124 2. List VRFs
 125
 126    To list VRFs that have been created:
 127        $ ip [-d] link show type vrf
 128          NOTE: The -d option is needed to show the table id
 129
 130    For example:
 131    $ ip -d link show type vrf
 132    11: vrf-mgmt: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
 133        link/ether 72:b3:ba:91:e2:24 brd ff:ff:ff:ff:ff:ff promiscuity 0
 134        vrf table 1 addrgenmode eui64
 135    12: vrf-red: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
 136        link/ether b6:6f:6e:f6:da:73 brd ff:ff:ff:ff:ff:ff promiscuity 0
 137        vrf table 10 addrgenmode eui64
 138    13: vrf-blue: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
 139        link/ether 36:62:e8:7d:bb:8c brd ff:ff:ff:ff:ff:ff promiscuity 0
 140        vrf table 66 addrgenmode eui64
 141    14: vrf-green: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
 142        link/ether e6:28:b8:63:70:bb brd ff:ff:ff:ff:ff:ff promiscuity 0
 143        vrf table 81 addrgenmode eui64
 144
 145
 146    Or in brief output:
 147
 148    $ ip -br link show type vrf
 149    vrf-mgmt         UP             72:b3:ba:91:e2:24 <NOARP,MASTER,UP,LOWER_UP>
 150    vrf-red          UP             b6:6f:6e:f6:da:73 <NOARP,MASTER,UP,LOWER_UP>
 151    vrf-blue         UP             36:62:e8:7d:bb:8c <NOARP,MASTER,UP,LOWER_UP>
 152    vrf-green        UP             e6:28:b8:63:70:bb <NOARP,MASTER,UP,LOWER_UP>
 153
 154
 155 3. Assign a Network Interface to a VRF
 156
 157    Network interfaces are assigned to a VRF by enslaving the netdevice to a
 158    VRF device:
 159        $ ip link set dev NAME master VRF-NAME
 160
 161    On enslavement connected and local routes are automatically moved to the
 162    table associated with the VRF device.
 163
 164    For example:
 165    $ ip link set dev eth0 master vrf-mgmt
 166
 167
 168 4. Show Devices Assigned to a VRF
 169
 170    To show devices that have been assigned to a specific VRF add the master
 171    option to the ip command:
 172        $ ip link show master VRF-NAME
 173
 174    For example:
 175    $ ip link show master vrf-red
 176    3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vrf-red state UP mode DEFAULT group default qlen 1000
 177        link/ether 02:00:00:00:02:02 brd ff:ff:ff:ff:ff:ff
 178    4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vrf-red state UP mode DEFAULT group default qlen 1000
 179        link/ether 02:00:00:00:02:03 brd ff:ff:ff:ff:ff:ff
 180    7: eth5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master vrf-red state DOWN mode DEFAULT group default qlen 1000
 181        link/ether 02:00:00:00:02:06 brd ff:ff:ff:ff:ff:ff
 182
 183
 184    Or using the brief output:
 185    $ ip -br link show master vrf-red
 186    eth1             UP             02:00:00:00:02:02 <BROADCAST,MULTICAST,UP,LOWER_UP>
 187    eth2             UP             02:00:00:00:02:03 <BROADCAST,MULTICAST,UP,LOWER_UP>
 188    eth5             DOWN           02:00:00:00:02:06 <BROADCAST,MULTICAST>
 189
 190
 191 5. Show Neighbor Entries for a VRF
 192
 193    To list neighbor entries associated with devices enslaved to a VRF device
 194    add the master option to the ip command:
 195        $ ip [-6] neigh show master VRF-NAME
 196
 197    For example:
 198    $  ip neigh show master vrf-red
 199    10.2.1.254 dev eth1 lladdr a6:d9:c7:4f:06:23 REACHABLE
 200    10.2.2.254 dev eth2 lladdr 5e:54:01:6a:ee:80 REACHABLE
 201
 202     $ ip -6 neigh show master vrf-red
 203     2002:1::64 dev eth1 lladdr a6:d9:c7:4f:06:23 REACHABLE
 204
 205
 206 6. Show Addresses for a VRF
 207
 208    To show addresses for interfaces associated with a VRF add the master
 209    option to the ip command:
 210        $ ip addr show master VRF-NAME
 211
 212    For example:
 213    $ ip addr show master vrf-red
 214    3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vrf-red state UP group default qlen 1000
 215        link/ether 02:00:00:00:02:02 brd ff:ff:ff:ff:ff:ff
 216        inet 10.2.1.2/24 brd 10.2.1.255 scope global eth1
 217           valid_lft forever preferred_lft forever
 218        inet6 2002:1::2/120 scope global
 219           valid_lft forever preferred_lft forever
 220        inet6 fe80::ff:fe00:202/64 scope link
 221           valid_lft forever preferred_lft forever
 222    4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vrf-red state UP group default qlen 1000
 223        link/ether 02:00:00:00:02:03 brd ff:ff:ff:ff:ff:ff
 224        inet 10.2.2.2/24 brd 10.2.2.255 scope global eth2
 225           valid_lft forever preferred_lft forever
 226        inet6 2002:2::2/120 scope global
 227           valid_lft forever preferred_lft forever
 228        inet6 fe80::ff:fe00:203/64 scope link
 229           valid_lft forever preferred_lft forever
 230    7: eth5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master vrf-red state DOWN group default qlen 1000
 231        link/ether 02:00:00:00:02:06 brd ff:ff:ff:ff:ff:ff
 232
 233    Or in brief format:
 234    $ ip -br addr show master vrf-red
 235    eth1             UP             10.2.1.2/24 2002:1::2/120 fe80::ff:fe00:202/64
 236    eth2             UP             10.2.2.2/24 2002:2::2/120 fe80::ff:fe00:203/64
 237    eth5             DOWN
 238
 239
 240 7. Show Routes for a VRF
 241
 242    To show routes for a VRF use the ip command to display the table associated
 243    with the VRF device:
 244        $ ip [-6] route show table ID
 245
 246    For example:
 247    $ ip route show table vrf-red
 248    prohibit default
 249    broadcast 10.2.1.0 dev eth1  proto kernel  scope link  src 10.2.1.2
 250    10.2.1.0/24 dev eth1  proto kernel  scope link  src 10.2.1.2
 251    local 10.2.1.2 dev eth1  proto kernel  scope host  src 10.2.1.2
 252    broadcast 10.2.1.255 dev eth1  proto kernel  scope link  src 10.2.1.2
 253    broadcast 10.2.2.0 dev eth2  proto kernel  scope link  src 10.2.2.2
 254    10.2.2.0/24 dev eth2  proto kernel  scope link  src 10.2.2.2
 255    local 10.2.2.2 dev eth2  proto kernel  scope host  src 10.2.2.2
 256    broadcast 10.2.2.255 dev eth2  proto kernel  scope link  src 10.2.2.2
 257
 258    $ ip -6 route show table vrf-red
 259    local 2002:1:: dev lo  proto none  metric 0  pref medium
 260    local 2002:1::2 dev lo  proto none  metric 0  pref medium
 261    2002:1::/120 dev eth1  proto kernel  metric 256  pref medium
 262    local 2002:2:: dev lo  proto none  metric 0  pref medium
 263    local 2002:2::2 dev lo  proto none  metric 0  pref medium
 264    2002:2::/120 dev eth2  proto kernel  metric 256  pref medium
 265    local fe80:: dev lo  proto none  metric 0  pref medium
 266    local fe80:: dev lo  proto none  metric 0  pref medium
 267    local fe80::ff:fe00:202 dev lo  proto none  metric 0  pref medium
 268    local fe80::ff:fe00:203 dev lo  proto none  metric 0  pref medium
 269    fe80::/64 dev eth1  proto kernel  metric 256  pref medium
 270    fe80::/64 dev eth2  proto kernel  metric 256  pref medium
 271    ff00::/8 dev vrf-red  metric 256  pref medium
 272    ff00::/8 dev eth1  metric 256  pref medium
 273    ff00::/8 dev eth2  metric 256  pref medium
 274
 275
 276 8. Route Lookup for a VRF
 277
 278    A test route lookup can be done for a VRF by adding the oif option to ip:
 279        $ ip [-6] route get oif VRF-NAME ADDRESS
 280
 281    For example:
 282    $ ip route get 10.2.1.40 oif vrf-red
 283    10.2.1.40 dev eth1  table vrf-red  src 10.2.1.2
 284        cache
 285
 286    $ ip -6 route get 2002:1::32 oif vrf-red
 287    2002:1::32 from :: dev eth1  table vrf-red  proto kernel  src 2002:1::2  metric 256  pref medium
 288
 289
 290 9. Removing Network Interface from a VRF
 291
 292    Network interfaces are removed from a VRF by breaking the enslavement to
 293    the VRF device:
 294        $ ip link set dev NAME nomaster
 295
 296    Connected routes are moved back to the default table and local entries are
 297    moved to the local table.
 298
 299    For example:
 300    $ ip link set dev eth0 nomaster
 301
 302 --------------------------------------------------------------------------------
 303
 304 Commands used in this example:
 305
 306 cat >> /etc/iproute2/rt_tables <<EOF
 307 1  vrf-mgmt
 308 10 vrf-red
 309 66 vrf-blue
 310 81 vrf-green
 311 EOF
 312
 313 function vrf_create
 314 {
 315     VRF=$1
 316     TBID=$2
 317     # create VRF device
 318     ip link add vrf-${VRF} type vrf table ${TBID}
 319
 320     # add rules that direct lookups to vrf table
 321     ip ru add pref 200 oif vrf-${VRF} table ${TBID}
 322     ip ru add pref 200 iif vrf-${VRF} table ${TBID}
 323     ip -6 ru add pref 200 oif vrf-${VRF} table ${TBID}
 324     ip -6 ru add pref 200 iif vrf-${VRF} table ${TBID}
 325
 326     if [ "${VRF}" != "mgmt" ]; then
 327         ip route add table ${TBID} prohibit default
 328     fi
 329     ip link set dev vrf-${VRF} up
 330     ip link set dev vrf-${VRF} state up
 331 }
 332
 333 vrf_create mgmt 1
 334 ip link set dev eth0 master vrf-mgmt
 335
 336 vrf_create red 10
 337 ip link set dev eth1 master vrf-red
 338 ip link set dev eth2 master vrf-red
 339 ip link set dev eth5 master vrf-red
 340
 341 vrf_create blue 66
 342 ip link set dev eth3 master vrf-blue
 343
 344 vrf_create green 81
 345 ip link set dev eth4 master vrf-green
 346
 347
 348 Interface addresses from /etc/network/interfaces:
 349 auto eth0
 350 iface eth0 inet static
 351       address 10.0.0.2
 352       netmask 255.255.255.0
 353       gateway 10.0.0.254
 354
 355 iface eth0 inet6 static
 356       address 2000:1::2
 357       netmask 120
 358
 359 auto eth1
 360 iface eth1 inet static
 361       address 10.2.1.2
 362       netmask 255.255.255.0
 363
 364 iface eth1 inet6 static
 365       address 2002:1::2
 366       netmask 120
 367
 368 auto eth2
 369 iface eth2 inet static
 370       address 10.2.2.2
 371       netmask 255.255.255.0
 372
 373 iface eth2 inet6 static
 374       address 2002:2::2
 375       netmask 120
 376
 377 auto eth3
 378 iface eth3 inet static
 379       address 10.2.3.2
 380       netmask 255.255.255.0
 381
 382 iface eth3 inet6 static
 383       address 2002:3::2
 384       netmask 120
 385
 386 auto eth4
 387 iface eth4 inet static
 388       address 10.2.4.2
 389       netmask 255.255.255.0
 390
 391 iface eth4 inet6 static
 392       address 2002:4::2
 393       netmask 120