1IPVSADM(8) Linux Administrator's Guide IPVSADM(8)
2
6 ipvsadm - Linux Virtual Server administration
7
9 ipvsadm -A|E -t|u|f service-address [-s scheduler]
10 [-p [timeout]] [-M netmask] [-b sched-flags]
11 ipvsadm -D -t|u|f service-address
12 ipvsadm -C
13 ipvsadm -R
14 ipvsadm -S [-n]
15 ipvsadm -a|e -t|u|f service-address -r server-address
16 [-g|i|m] [-w weight] [-x upper] [-y lower]
17 ipvsadm -d -t|u|f service-address -r server-address
18 ipvsadm -L|l [options]
19 ipvsadm -Z [-t|u|f service-address]
20 ipvsadm --set tcp tcpfin udp
21 ipvsadm --start-daemon state [--mcast-interface interface]
22 [--syncid syncid]
23 ipvsadm --stop-daemon state
24 ipvsadm -h
25
27 Ipvsadm(8) is used to set up, maintain or inspect the virtual server
28 table in the Linux kernel. The Linux Virtual Server can be used to
29 build scalable network services based on a cluster of two or more
30 nodes. The active node of the cluster redirects service requests to a
31 collection of server hosts that will actually perform the services.
32 Supported features include two protocols (TCP and UDP), three packet-
33 forwarding methods (NAT, tunneling, and direct routing), and eight load
34 balancing algorithms (round robin, weighted round robin, least-connec‐
35 tion, weighted least-connection, locality-based least-connection,
36 locality-based least-connection with replication, destination-hashing,
37 and source-hashing).
38 The command has two basic formats for execution:
40 ipvsadm COMMAND [protocol] service-address
42 [scheduling-method] [persistence options]
43 ipvsadm command [protocol] service-address
45 server-address [packet-forwarding-method]
46 [weight options]
47 The first format manipulates a virtual service and the algorithm for
49 assigning service requests to real servers. Optionally, a persistent
50 timeout and network mask for the granularity of a persistent service
51 may be specified. The second format manipulates a real server that is
52 associated with an existing virtual service. When specifying a real
53 server, the packet-forwarding method and the weight of the real server,
54 relative to other real servers for the virtual service, may be speci‐
55 fied, otherwise defaults will be used.
56 COMMANDS
58 ipvsadm(8) recognises the commands described below. Upper-case commands
59 maintain virtual services. Lower-case commands maintain real servers
60 that are associated with a virtual service.
61 -A, --add-service
63 Add a virtual service. A service address is uniquely defined by
64 a triplet: IP address, port number, and protocol. Alternatively,
65 a virtual service may be defined by a firewall-mark.
66 -E, --edit-service
68 Edit a virtual service.
69 -D, --delete-service
71 Delete a virtual service, along with any associated real
72 servers.
73 -C, --clear
75 Clear the virtual server table.
76 -R, --restore
78 Restore Linux Virtual Server rules from stdin. Each line read
79 from stdin will be treated as the command line options to a sep‐
80 arate invocation of ipvsadm. Lines read from stdin can option‐
81 ally begin with "ipvsadm". This option is useful to avoid exe‐
82 cuting a large number or ipvsadm commands when constructing an
83 extensive routing table.
84 -S, --save
86 Dump the Linux Virtual Server rules to stdout in a format that
87 can be read by -R|--restore.
88 -a, --add-server
90 Add a real server to a virtual service.
91 -e, --edit-server
93 Edit a real server in a virtual service.
94 -d, --delete-server
96 Remove a real server from a virtual service.
97 -L, -l, --list
99 List the virtual server table if no argument is specified. If a
100 service-address is selected, list this service only. If the -c
101 option is selected, then display the connection table. The exact
102 output is affected by the other arguments given.
103 -Z, --zero
105 Zero the packet, byte and rate counters in a service or all ser‐
106 vices.
107 --set tcp tcpfin udp
109 Change the timeout values used for IPVS connections. This com‐
110 mand always takes 3 parameters, representing the timeout
111 values (in seconds) for TCP sessions, TCP sessions after receiv‐
112 ing a FIN packet, and UDP packets, respectively. A timeout
113 value 0 means that the current timeout value of the correspond‐
114 ing entry is preserved.
115 --start-daemon state
117 Start the connection synchronization daemon. The state is to
118 indicate that the daemon is started as master or backup. The
119 connection synchronization daemon is implemented inside the
120 Linux kernel. The master daemon running at the primary load bal‐
121 ancer multicasts changes of connections periodically, and the
122 backup daemon running at the backup load balancers receives mul‐
123 ticast message and creates corresponding connections. Then, in
124 case the primary load balancer fails, a backup load balancer
125 will takeover, and it has state of almost all connections, so
126 that almost all established connections can continue to access
127 the service.
128 The sync daemon currently only supports IPv4 connections.
130 --stop-daemon
132 Stop the connection synchronization daemon.
133 -h, --help
135 Display a description of the command syntax.
136 PARAMETERS
138 The commands above accept or require zero or more of the following
139 parameters.
140 -t, --tcp-service service-address
142 Use TCP service. The service-address is of the form host[:port].
143 Host may be one of a plain IP address or a hostname. Port may be
144 either a plain port number or the service name of port. The Port
145 may be omitted, in which case zero will be used. A Port of zero
146 is only valid if the service is persistent as the -p|--persis‐
147 tent option, in which case it is a wild-card port, that is con‐
148 nections will be accepted to any port.
149 -u, --udp-service service-address
151 Use UDP service. See the -t|--tcp-service for the description of
152 the service-address.
153 -f, --fwmark-service integer
155 Use a firewall-mark, an integer value greater than zero, to
156 denote a virtual service instead of an address, port and proto‐
157 col (UDP or TCP). The marking of packets with a firewall-mark is
158 configured using the -m|--mark option to iptables(8). It can be
159 used to build a virtual service associated with the same real
160 servers, covering multiple IP address, port and protocol
161 triplets. If IPv6 addresses are used, the -6 option must be
162 used.
163 Using firewall-mark virtual services provides a convenient
165 method of grouping together different IP addresses, ports and
166 protocols into a single virtual service. This is useful for both
167 simplifying configuration if a large number of virtual services
168 are required and grouping persistence across what would other‐
169 wise be multiple virtual services.
170 -s, --scheduler scheduling-method
172 scheduling-method Algorithm for allocating TCP connections and
173 UDP datagrams to real servers. Scheduling algorithms are imple‐
174 mented as kernel modules. Ten are shipped with the Linux Virtual
175 Server:
176 rr - Round Robin: distributes jobs equally amongst the available
178 real servers.
179 wrr - Weighted Round Robin: assigns jobs to real servers propor‐
181 tionally to there real servers' weight. Servers with higher
182 weights receive new jobs first and get more jobs than servers
183 with lower weights. Servers with equal weights get an equal dis‐
184 tribution of new jobs.
185 lc - Least-Connection: assigns more jobs to real servers with
187 fewer active jobs.
188 wlc - Weighted Least-Connection: assigns more jobs to servers
190 with fewer jobs and relative to the real servers' weight
191 (Ci/Wi). This is the default.
192 lblc - Locality-Based Least-Connection: assigns jobs destined
194 for the same IP address to the same server if the server is not
195 overloaded and available; otherwise assign jobs to servers with
196 fewer jobs, and keep it for future assignment.
197 lblcr - Locality-Based Least-Connection with Replication:
199 assigns jobs destined for the same IP address to the least-con‐
200 nection node in the server set for the IP address. If all the
201 node in the server set are over loaded, it picks up a node with
202 fewer jobs in the cluster and adds it in the sever set for the
203 target. If the server set has not been modified for the speci‐
204 fied time, the most loaded node is removed from the server set,
205 in order to avoid high degree of replication.
206 dh - Destination Hashing: assigns jobs to servers through look‐
208 ing up a statically assigned hash table by their destination IP
209 addresses.
210 sh - Source Hashing: assigns jobs to servers through looking up
212 a statically assigned hash table by their source IP addresses.
213 This scheduler has two flags: sh-fallback, which enables fall‐
214 back to a different server if the selected server was unavail‐
215 able, and sh-port, which adds the source port number to the hash
216 computation.
217 sed - Shortest Expected Delay: assigns an incoming job to the
219 server with the shortest expected delay. The expected delay that
220 the job will experience is (Ci + 1) / Ui if sent to the ith
221 server, in which Ci is the number of jobs on the the ith server
222 and Ui is the fixed service rate (weight) of the ith server.
223 nq - Never Queue: assigns an incoming job to an idle server if
225 there is, instead of waiting for a fast one; if all the servers
226 are busy, it adopts the Shortest Expected Delay policy to assign
227 the job.
228 -p, --persistent [timeout]
230 Specify that a virtual service is persistent. If this option is
231 specified, multiple requests from a client are redirected to the
232 same real server selected for the first request. Optionally,
233 the timeout of persistent sessions may be specified given in
234 seconds, otherwise the default of 300 seconds will be used. This
235 option may be used in conjunction with protocols such as SSL or
236 FTP where it is important that clients consistently connect with
237 the same real server.
238 Note: If a virtual service is to handle FTP connections then
240 persistence must be set for the virtual service if Direct Rout‐
241 ing or Tunnelling is used as the forwarding mechanism. If Mas‐
242 querading is used in conjunction with an FTP service than per‐
243 sistence is not necessary, but the ip_vs_ftp kernel module must
244 be used. This module may be manually inserted into the kernel
245 using insmod(8).
246 -M, --netmask netmask
248 Specify the granularity with which clients are grouped for per‐
249 sistent virtual services. The source address of the request is
250 masked with this netmask to direct all clients from a network to
251 the same real server. The default is 255.255.255.255, that is,
252 the persistence granularity is per client host. Less specific
253 netmasks may be used to resolve problems with non-persistent
254 cache clusters on the client side. IPv6 netmasks should be
255 specified as a prefix length between 1 and 128. The default
256 prefix length is 128.
257 -b, --sched-flags sched-flags
259 Set scheduler flags for this virtual server. sched-flags is a
260 comma-separated list of flags. See the scheduler descriptions
261 for valid scheduler flags.
262 -r, --real-server server-address
264 Real server that an associated request for service may be
265 assigned to. The server-address is the host address of a real
266 server, and may plus port. Host can be either a plain IP address
267 or a hostname. Port can be either a plain port number or the
268 service name of port. In the case of the masquerading method,
269 the host address is usually an RFC 1918 private IP address, and
270 the port can be different from that of the associated service.
271 With the tunneling and direct routing methods, port must be
272 equal to that of the service address. For normal services, the
273 port specified in the service address will be used if port is
274 not specified. For fwmark services, port may be omitted, in
275 which case the destination port on the real server will be the
276 destination port of the request sent to the virtual service.
277 [packet-forwarding-method]
279 -g, --gatewaying Use gatewaying (direct routing). This is the
281 default.
282 -i, --ipip Use ipip encapsulation (tunneling).
284 -m, --masquerading Use masquerading (network access transla‐
286 tion, or NAT).
287 Note: Regardless of the packet-forwarding mechanism specified,
289 real servers for addresses for which there are interfaces on the
290 local node will be use the local forwarding method, then packets
291 for the servers will be passed to upper layer on the local node.
292 This cannot be specified by ipvsadm, rather it set by the kernel
293 as real servers are added or modified.
294 -w, --weight weight
296 Weight is an integer specifying the capacity of a server rela‐
297 tive to the others in the pool. The valid values of weight are 0
298 through to 65535. The default is 1. Quiescent servers are speci‐
299 fied with a weight of zero. A quiescent server will receive no
300 new jobs but still serve the existing jobs, for all scheduling
301 algorithms distributed with the Linux Virtual Server. Setting a
302 quiescent server may be useful if the server is overloaded or
303 needs to be taken out of service for maintenance.
304 -x, --u-threshold uthreshold
306 uthreshold is an integer specifying the upper connection thresh‐
307 old of a server. The valid values of uthreshold are 0 through to
308 65535. The default is 0, which means the upper connection
309 threshold is not set. If uthreshold is set with other values, no
310 new connections will be sent to the server when the number of
311 its connections exceeds its upper connection threshold.
312 -y, --l-threshold lthreshold
314 lthreshold is an integer specifying the lower connection thresh‐
315 old of a server. The valid values of lthreshold are 0 through to
316 65535. The default is 0, which means the lower connection
317 threshold is not set. If lthreshold is set with other values,
318 the server will receive new connections when the number of its
319 connections drops below its lower connection threshold. If
320 lthreshold is not set but uthreshold is set, the server will
321 receive new connections when the number of its connections drops
322 below three forth of its upper connection threshold.
323 --mcast-interface interface
325 Specify the multicast interface that the sync master daemon
326 sends outgoing multicasts through, or the sync backup daemon
327 listens to for multicasts.
328 --syncid syncid
330 Specify the syncid that the sync master daemon fills in the Syn‐
331 cID header while sending multicast messages, or the sync backup
332 daemon uses to filter out multicast messages not matched with
333 the SyncID value. The valid values of syncid are 0 through to
334 255. The default is 0, which means no filtering at all.
335 -c, --connection
337 Connection output. The list command with this option will list
338 current IPVS connections.
339 --timeout
341 Timeout output. The list command with this option will display
342 the timeout values (in seconds) for TCP sessions, TCP sessions
343 after receiving a FIN packet, and UDP packets.
344 --daemon
346 Daemon information output. The list command with this option
347 will display the daemon status and its multicast interface.
348 --stats
350 Output of statistics information. The list command with this
351 option will display the statistics information of services and
352 their servers.
353 --rate Output of rate information. The list command with this option
355 will display the rate information (such as connections/second,
356 bytes/second and packets/second) of services and their servers.
357 --thresholds
359 Output of thresholds information. The list command with this
360 option will display the upper/lower connection threshold infor‐
361 mation of each server in service listing.
362 --persistent-conn
364 Output of persistent connection information. The list command
365 with this option will display the persistent connection counter
366 information of each server in service listing. The persistent
367 connection is used to forward the actual connections from the
368 same client/network to the same server.
369 The list command with the -c, --connection option and this
371 option will include persistence engine data, if any is present,
372 when listing connections.
373 --sort Sort the list of virtual services and real servers. The virtual
375 service entries are sorted in ascending order by <protocol,
376 address, port>. The real server entries are sorted in ascending
377 order by <address, port>. (default)
378 --nosort
380 Do not sort the list of virtual services and real servers.
381 -n, --numeric
383 Numeric output. IP addresses and port numbers will be printed
384 in numeric format rather than as as host names and services
385 respectively, which is the default.
386 --exact
388 Expand numbers. Display the exact value of the packet and byte
389 counters, instead of only the rounded number in K's (multiples
390 of 1000) M's (multiples of 1000K) or G's (multiples of 1000M).
391 This option is only relevant for the -L command.
392 -6, --ipv6
394 Use with -f to signify fwmark rule uses IPv6 addresses.
395 -o, --ops
397 One-packet scheduling. Used in conjunction with a UDP virtual
398 service or a fwmark virtual service that handles only UDP pack‐
399 ets. All connections are created such that they only schedule
400 one packet.
401
403 The following commands configure a Linux Director to distribute incom‐
404 ing requests addressed to port 80 on 207.175.44.110 equally to port 80
405 on five real servers. The forwarding method used in this example is
406 NAT, with each of the real servers being masqueraded by the Linux
407 Director.
408 ipvsadm -A -t 207.175.44.110:80 -s rr
410 ipvsadm -a -t 207.175.44.110:80 -r 192.168.10.1:80 -m
411 ipvsadm -a -t 207.175.44.110:80 -r 192.168.10.2:80 -m
412 ipvsadm -a -t 207.175.44.110:80 -r 192.168.10.3:80 -m
413 ipvsadm -a -t 207.175.44.110:80 -r 192.168.10.4:80 -m
414 ipvsadm -a -t 207.175.44.110:80 -r 192.168.10.5:80 -m
415 Alternatively, this could be achieved in a single ipvsadm command.
417 echo "
419 -A -t 207.175.44.110:80 -s rr
420 -a -t 207.175.44.110:80 -r 192.168.10.1:80 -m
421 -a -t 207.175.44.110:80 -r 192.168.10.2:80 -m
422 -a -t 207.175.44.110:80 -r 192.168.10.3:80 -m
423 -a -t 207.175.44.110:80 -r 192.168.10.4:80 -m
424 -a -t 207.175.44.110:80 -r 192.168.10.5:80 -m
425 " | ipvsadm -R
426 As masquerading is used as the forwarding mechanism in this example,
428 the default route of the real servers must be set to the linux direc‐
429 tor, which will need to be configured to forward and masquerade pack‐
430 ets. This can be achieved using the following commands:
431 echo "1" > /proc/sys/net/ipv4/ip_forward
433
435 The following commands configure a Linux Director to distribute incom‐
436 ing requests addressed to any port on 207.175.44.110 or 207.175.44.111
437 equally to the corresponding port on five real servers. As per the pre‐
438 vious example, the forwarding method used in this example is NAT, with
439 each of the real servers being masqueraded by the Linux Director.
440 ipvsadm -A -f 1 -s rr
442 ipvsadm -a -f 1 -r 192.168.10.1:0 -m
443 ipvsadm -a -f 1 -r 192.168.10.2:0 -m
444 ipvsadm -a -f 1 -r 192.168.10.3:0 -m
445 ipvsadm -a -f 1 -r 192.168.10.4:0 -m
446 ipvsadm -a -f 1 -r 192.168.10.5:0 -m
447 As masquerading is used as the forwarding mechanism in this example,
449 the default route of the real servers must be set to the linux direc‐
450 tor, which will need to be configured to forward and masquerade pack‐
451 ets. The real server should also be configured to mark incoming packets
452 addressed to any port on 207.175.44.110 and 207.175.44.111 with fire‐
453 wall-mark 1. If FTP traffic is to be handled by this virtual service,
454 then the ip_vs_ftp kernel module needs to be inserted into the kernel.
455 These operations can be achieved using the following commands:
456 echo "1" > /proc/sys/net/ipv4/ip_forward
458 modprobe ip_tables
459 iptables -A PREROUTING -t mangle -d 207.175.44.110/31 -j MARK --set-mark 1
460 modprobe ip_vs_ftp
461
463 IPv6 addresses should be surrounded by square brackets ([ and ]).
464 ipvsadm -A -t [2001:db8::80]:80 -s rr
466 ipvsadm -a -t [2001:db8::80]:80 -r [2001:db8::a0a0]:80 -m
467 fwmark IPv6 services require the -6 option.
469
471 The Linux Virtual Server implements three defense strategies against
472 some types of denial of service (DoS) attacks. The Linux Director cre‐
473 ates an entry for each connection in order to keep its state, and each
474 entry occupies 128 bytes effective memory. LVS's vulnerability to a DoS
475 attack lies in the potential to increase the number entries as much as
476 possible until the linux director runs out of memory. The three defense
477 strategies against the attack are: Randomly drop some entries in the
478 table. Drop 1/rate packets before forwarding them. And use secure tcp
479 state transition table and short timeouts. The strategies are con‐
480 trolled by sysctl variables and corresponding entries in the /proc
481 filesystem:
482 /proc/sys/net/ipv4/vs/drop_entry /proc/sys/net/ipv4/vs/drop_packet
484 /proc/sys/net/ipv4/vs/secure_tcp
485 Valid values for each variable are 0 through to 3. The default value is
487 0, which disables the respective defense strategy. 1 and 2 are auto‐
488 matic modes - when there is no enough available memory, the respective
489 strategy will be enabled and the variable is automatically set to 2,
490 otherwise the strategy is disabled and the variable is set to 1. A
491 value of 3 denotes that the respective strategy is always enabled. The
492 available memory threshold and secure TCP timeouts can be tuned using
493 the sysctl variables and corresponding entries in the /proc filesystem:
494 /proc/sys/net/ipv4/vs/amemthresh /proc/sys/net/ipv4/vs/timeout_*
496
498 /proc/net/ip_vs
499 /proc/net/ip_vs_app
500 /proc/net/ip_vs_conn
501 /proc/net/ip_vs_stats
502 /proc/sys/net/ipv4/vs/am_droprate
503 /proc/sys/net/ipv4/vs/amemthresh
504 /proc/sys/net/ipv4/vs/drop_entry
505 /proc/sys/net/ipv4/vs/drop_packet
506 /proc/sys/net/ipv4/vs/secure_tcp
507 /proc/sys/net/ipv4/vs/timeout_close
508 /proc/sys/net/ipv4/vs/timeout_closewait
509 /proc/sys/net/ipv4/vs/timeout_established
510 /proc/sys/net/ipv4/vs/timeout_finwait
511 /proc/sys/net/ipv4/vs/timeout_icmp
512 /proc/sys/net/ipv4/vs/timeout_lastack
513 /proc/sys/net/ipv4/vs/timeout_listen
514 /proc/sys/net/ipv4/vs/timeout_synack
515 /proc/sys/net/ipv4/vs/timeout_synrecv
516 /proc/sys/net/ipv4/vs/timeout_synsent
517 /proc/sys/net/ipv4/vs/timeout_timewait
518 /proc/sys/net/ipv4/vs/timeout_udp
519
521 The LVS web site (http://www.linuxvirtualserver.org/) for more documen‐
522 tation about LVS.
523 ipvsadm-save(8), ipvsadm-restore(8), iptables(8),
525 insmod(8), modprobe(8)
526
528 ipvsadm - Wensong Zhang <wensong@linuxvirtualserver.org>
529 Peter Kese <peter.kese@ijs.si>
530 man page - Mike Wangsmo <wanger@redhat.com>
531 Wensong Zhang <wensong@linuxvirtualserver.org>
532 Horms <horms@verge.net.au>
5334th Berkeley Distribution 5th July 2003 IPVSADM(8)