Table Of Contents
ip tcp compression-connections
ip slb probe custom udp
To configure a custom User Datagram Protocol (UDP) probe name and enter custom UDP probe configuration mode, use the ip slb probe custom udp command in global configuration mode. To remove a custom UDP probe name, use the no form of this command.
ip slb probe probe custom udp
no ip slb probe probe
Syntax Description
Defaults
No custom UDP probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command configures the custom UDP probe name and application protocol and enters custom UDP configuration mode.
The custom UDP probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE6, then enters custom UDP probe configuration mode:
Router(config)# ip slb probe PROBE6 custom udpRelated Commands
ip slb probe dns
To configure a Domain Name System (DNS) probe name and enter DNS probe configuration mode, use the ip slb probe dns command in global configuration mode. To remove a DNS probe name, use the no form of this command.
ip slb probe probe dns
no ip slb probe probe
Syntax Description
Defaults
No DNS probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
DNS probes send domain name resolve requests to real servers and verify the returned IP addresses.
This command configures the DNS probe name and application protocol and enters DNS configuration mode.
The DNS probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE4, then enters DNS probe configuration mode:
Router(config)# ip slb probe PROBE4 dnsRelated Commands
ip slb probe http
To configure an HTTP probe name and enter HTTP probe configuration mode, use the ip slb probe http command in global configuration mode. To remove an HTTP probe name, use the no form of this command.
ip slb probe probe http
no ip slb probe probe
Syntax Description
Defaults
No HTTP probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command configures the HTTP probe name and application protocol and enters HTTP configuration mode.
The HTTP probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Note
HTTP probes require a route to the virtual server. The route is not used, but it must exist to enable the sockets code to verify that the destination can be reached, which in turn is essential for HTTP probes to function correctly. The route can be either a host route (advertised by the virtual server) or a default route (specified using the ip route 0.0.0.0 0.0.0.0 command, for example).
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE2, then enters HTTP probe configuration mode:
Router(config)# ip slb probe PROBE2 httpRelated Commands
ip slb probe ping
To configure a ping probe name and enter ping probe configuration mode, use the ip slb probe ping command in global configuration mode. To remove a ping probe name, use the no form of this command.
ip slb probe probe ping
no ip slb probe probe
Syntax Description
Defaults
No ping probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command configures the ping probe name and application protocol and enters ping configuration mode.
The ping probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE1, then enters ping probe configuration mode:
Router(config)# ip slb probe PROBE1 pingRelated Commands
ip slb probe tcp
To configure a TCP probe name and enter TCP probe configuration mode, use the ip slb probe tcp command in global configuration mode. To remove a TCP probe name, use the no form of this command.
ip slb probe probe tcp
no ip slb probe probe
Syntax Description
Defaults
No TCP probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command configures the TCP probe name and application protocol and enters TCP configuration mode.
The TCP probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE5, then enters TCP probe configuration mode:
Router(config)# ip slb probe PROBE5 tcpRelated Commands
ip slb probe wsp
To configure a Wireless Session Protocol (WSP) probe name and enter WSP probe configuration mode, use the ip slb probe wsp command in global configuration mode. To remove a WSP probe name, use the no form of this command.
ip slb probe probe wsp
no ip slb probe probe
Syntax Description
Defaults
No WSP probe is configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command configures the WSP probe name and application protocol and enters WSP probe configuration mode.
The WSP probe cannot be unconfigured while it is being used by the server farm or firewall farm.
You can configure more than one probe, in any combination of supported types, for each server farm or for each firewall in a firewall farm.
Examples
The following example configures an IOS Server Load Balancing (IOS SLB) probe named PROBE3, then enters WSP probe configuration mode:
Router(config)# ip slb probe PROBE3 wspRelated Commands
ip slb replicate slave rate
To set the replication message rate for IOS Server Load Balancing (IOS SLB) slave replication, use the ip slb replicate slave rate command in global configuration mode. To restore the default rate, use the no form of this command.
ip slb replicate slave rate rate
no ip slb replicate slave rate rate
Syntax Description
Defaults
The default rate is 400 messages per second.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command enables you to manage Interprocess Communication Channel (IPC) resources between two route processors. If there is congestion between the two route processors, use this command to set a lower rate.
If the replication rate is exceeded, IOS SLB issues an appropriate error message.
General packet radio service (GPRS) load balancing without GPRS Tunneling Protocol (GTP) cause code inspection enabled does not support the ip slb replicate slave rate command in global configuration mode.
The Home Agent Director does not support the ip slb replicate slave rate command in global configuration mode.
Examples
The following example sets the replication message rate to 500 messages per second:
Router(config)# ip slb replicate slave rate 500Related Commands
ip slb route
To enable IOS Server Load Balancing (IOS SLB) to route packets using the RADIUS framed-IP sticky database, or to route packets from one firewall real server back through another firewall real server, use the ip slb route command in global configuration mode. To route packets normally, use the no form of this command.
ip slb route {framed-ip deny | ip-address netmask framed-ip | inter-firewall}
no ip slb route {framed-ip deny | ip-address netmask framed-ip | inter-firewall}
Syntax Description
Defaults
Cisco IOS SLB cannot route packets using the RADIUS framed-IP sticky database, nor can it route packets from one firewall real server back through another firewall real server.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command enables IOS SLB to inspect packets whose source IP addresses match the specified IP address and subnet mask. IOS SLB then searches for the packet's source IP address in the RADIUS framed-IP sticky database. If the database contains a matching entry, IOS SLB routes the packet to the associated real server. If the database does not contain a matching entry, IOS SLB routes the packet normally.
The inter-firewall keyword is useful when traffic is arriving from an address behind a firewall, is destined for an address behind a firewall, and has a sticky entry to be routed via the routing table.
Examples
The following example enables IOS SLB to inspect packets with the source IP address 10.10.10.1:
Router(config)# ip slb route 10.10.10.1 255.255.255.255 framed-ipRelated Commands
ip slb serverfarm
To identify a server farm and enter SLB server farm configuration mode, use the ip slb serverfarm command in global configuration mode. To remove the server farm from the IOS Server Load Balancing (IOS SLB) configuration, use the no form of this command.
ip slb serverfarm server-farm
no ip slb serverfarm server-farm
Syntax Description
server-farm
Character string used to identify the server farm. The character string is limited to 15 characters.
Defaults
No server farm is identified.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
Grouping real servers into server farms is an essential part of IOS SLB. Using server farms enables IOS SLB to assign new connections to the real servers based on their weighted capacities, and on the load-balancing algorithms used.
Examples
The following example identifies a server farm named PUBLIC:
Router(config)# ip slb serverfarm PUBLICRouter(config-slb-sfarm)#Related Commands
real (server farm)
Identifies a real server by IP address and optional port number as a member of a server farm and enters real server configuration mode.
ip slb static
To configure a real server's Network Address Translation (NAT) behavior and enter static NAT configuration mode, use the ip slb static command in global configuration mode. To restore the real server's default NAT behavior, use the no form of this command.
ip slb static {drop | nat {virtual | virtual-ip [per-packet | sticky]}}
no ip slb static {drop | nat {virtual | virtual-ip [per-packet | sticky]}}
Syntax Description
Defaults
If you do not specify either the per-packet or sticky keyword, IOS SLB maintains connection state for packets originating from the real server.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
If you specify the virtual-ip argument and you do not specify the per-packet option, IOS SLB uses server port translation to distinguish between connection requests initiated by different real servers.
Examples
The following example specifies that the real server is to use server NAT and to use virtual IP address 10.1.10.1 when translating addresses, and that IOS SLB is not to maintain connection state for any packets originating from the real server:
Router(config)# ip slb static nat 10.1.10.1 per-packetRelated Commands
ip slb timers gtp gsn
To change the amount of time IOS Server Load Balancing (IOS SLB) maintains sessions to and from an idle gateway general packet radio service (GPRS) support node (GGSN) or serving GPRS support node (SGSN), use the ip slb timers gtp gsn command in global configuration mode. To restore the default GPRS support node (GSN) idle timer, use the no form of this command.
ip slb timers gtp gsn duration
no ip slb timers gtp gsn duration
Syntax Description
Defaults
The default duration is 90 seconds.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command sets the GSN idle timer for all IOS SLB virtual servers that are configured for GPRS Tunneling Protocol (GTP) cause code inspection. When the GSN idle timer expires, IOS SLB destroys all sessions to and from the idle GGSN or SGSN.
Examples
The following example specifies that IOS SLB maintains sessions for 45 seconds after a GGSN or SGSN becomes idle:
Router(config)# ip slb timers gtp gsn 45Related Commands
ip slb vserver
To identify a virtual server and enter SLB virtual server configuration mode, use the ip slb vserver command in global configuration mode. To remove a virtual server from the IOS Server Load Balancing (IOS SLB) configuration, use the no form of this command.
ip slb vserver virtual-server
no ip slb vserver virtual-server
Syntax Description
virtual-server
Character string used to identify the virtual server. The character string is limited to 15 characters.
Defaults
No virtual server is identified.
Command Modes
Global configuration (config)
Command History
Examples
The following example identifies a virtual server named PUBLIC_HTTP:
Router(config)# ip slb vserver PUBLIC_HTTPRouter(config-slb-vserver)#Related Commands
ip tcp adjust-mss
To adjust the maximum segment size (MSS) value of TCP synchronize/start (SYN) packets going through a router, use the ip tcp adjust-mss command in interface configuration mode. To return the MSS value to the default setting, use the no form of this command.
ip tcp adjust-mss max-segment-size
no ip tcp adjust-mss max-segment-size
Syntax Description
Command Default
The MSS is determined by the originating host.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
When a host (usually a PC) initiates a TCP session with a server, it negotiates the IP segment size by using the MSS option field in the TCP SYN packet. The value of the MSS field is determined by the maximum transmission unit (MTU) configuration on the host. The default MSS value for a PC is 1500 bytes.
The PPP over Ethernet (PPPoE) standard supports an MTU of only 1492 bytes. The disparity between the host and PPPoE MTU size can cause the router in between the host and the server to drop 1500-byte packets and terminate TCP sessions over the PPPoE network. Even if the path MTU (which detects the correct MTU across the path) is enabled on the host, sessions may be dropped because system administrators sometimes disable the Internet Control Message Protocol (ICMP) error messages that must be relayed from the host in order for path MTU to work.
The ip tcp adjust-mss command helps prevent TCP sessions from being dropped by adjusting the MSS value of the TCP SYN packets.
The ip tcp adjust-mss command is effective only for TCP connections passing through the router.
In most cases, the optimum value for the max-segment-size argument is 1452 bytes. This value plus the 20-byte IP header, the 20-byte TCP header, and the 8-byte PPPoE header add up to a 1500-byte packet that matches the MTU size for the Ethernet link.
If you are configuring the ip mtu command on the same interface as the ip tcp adjust-mss command, we recommend that you use the following commands and values:
•
•
Examples
The following example shows the configuration of a PPPoE client with the MSS value set to 1452:
vpdn enableno vpdn logging!vpdn-group 1request-dialinprotocol pppoe!interface Ethernet0ip address 192.168.100.1.255.255.255.0ip tcp adjust-mss 1452ip nat inside!interface ATM0no ip addressno atm ilmi-keepalivepvc 8/35pppoe client dial-pool-number 1!dsl equipment-type CPEdsl operating-mode GSHDSL symmetric annex Bdsl linerate AUTO!interface Dialer1ip address negotiatedip mtu 1492ip nat outsideencapsulation pppdialer pool 1dialer-group 1ppp authentication pap callinppp pap sent-username sohodyn password 7 141B1309000528!ip nat inside source list 101 Dialer1 overloadip route 0.0.0.0.0.0.0.0 Dialer1access-list permit ip 192.168.100.0.0.0.0.255 anyRelated Commands
ip tcp chunk-size
To alter the TCP maximum read size for Telnet or rlogin, use the ip tcp chunk-size command in global configuration mode. To restore the default value, use the no form of this command.
ip tcp chunk-size characters
no ip tcp chunk-size
Syntax Description
Defaults
0, which Telnet and rlogin interpret as the largest possible 32-bit positive number.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
It is unlikely you will need to change the default value.
Examples
The following example sets the maximum TCP read size to 64,000 bytes:
ip tcp chunk-size 64000ip tcp compression-connections
To specify the total number of Transmission Control Protocol (TCP) header compression connections that can exist on an interface, use the ip tcp compression-connections command in interface configuration mode. To restore the default, use the no form of this command.
ip tcp compression-connections number
no ip tcp compression-connections
Syntax Description
Command Default
For PPP and High-Level Data Link Control (HDLC) interfaces, the default is 16 compression connections.
For Frame Relay interfaces, the default is 256 compression connections.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
You should configure one connection for each TCP connection through the specified interface.
Each connection sets up a compression cache entry, so you are in effect specifying the maximum number of cache entries and the size of the cache. Too few cache entries for the specified interface can lead to degraded performance, and too many cache entries can lead to wasted memory.
Note
Examples
The following example sets the first serial interface for header compression with a maximum of ten cache entries:
Router> enableRouter# configure terminalRouter(config)# interface serial 0Router(config-if)# ip tcp header-compressionRouter(config-if)# ip tcp compression-connections 10Router(config-if)# endRelated Commands
ip tcp header-compression
Enables TCP header compression.
show ip tcp header-compressions
Displays TCP header compression statistics.
ip tcp ecn
To enable TCP Explicit Congestion Notification (ECN), use the ip tcp ecn command in global configuration mode. To disable TCP ECN, use the no form of this command.
ip tcp ecn
no ip tcp ecn
Syntax Description
This command has no arguments or keywords.
Command Default
TCP ECN is disabled.
Command Modes
Global configuration (config)
Command History
12.3(7)T
This command was introduced.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
Examples
The following example shows how to enable TCP ECN:
ip tcp ecnRelated Commands
debug ip tcp ecn
Turns on TCP ECN debugging.
show tcp tcb
Displays the status of local and remote end hosts.
ip tcp header-compression
To enable Transmission Control Protocol (TCP) header compression, use the ip tcp header-compression command in interface configuration mode. To disable compression, use the no form of this command.
ip tcp header-compression [passive | iphc-format | ietf-format]
no ip tcp header-compression [passive | iphc-format | ietf-format]
Syntax Description
Command Default
Disabled
For PPP interfaces, the default format for header compression is the IPHC format.
For High-Level Data Link Control (HDLC) and Frame Relay interfaces, the default format is as described in RFC 1144, Compressing TCP/IP Headers for Low-Speed Serial Links.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
You can compress the headers of your TCP/IP packets in order to reduce the size of your packets. TCP header compression is supported on serial lines using Frame Relay, HDLC, or PPP encapsulation. You must enable compression on both ends of a serial connection. Compressing the TCP header can speed up Telnet connections dramatically.
In general, TCP header compression is advantageous when your traffic consists of many small packets, not for traffic that consists of large packets. Transaction processing (usually using terminals) tends to use small packets and file transfers use large packets. This feature only compresses the TCP header, so it has no effect on User Datagram Protocol (UDP) packets or other protocol headers.
The passive Keyword
By default, the ip tcp header-compression command compresses outgoing TCP traffic. If you specify the passive keyword, outgoing TCP traffic is compressed only if incoming TCP traffic on the same interface is compressed. If you do not specify the passive keyword, all outgoing TCP traffic is compressed.
For PPP interfaces, the passive keyword is ignored. PPP interfaces negotiate the use of header-compression, regardless of whether the passive keyword is specified. Therefore, on PPP interfaces, the passive keyword is replaced by the IPHC format, the default format for PPP interfaces.
The iphc-format Keyword
The iphc-format keyword indicates that the IPHC format of header compression will be used. For PPP and HDLC interfaces, when the iphc-format keyword is specified, Real-Time Transport Protocol (RTP) header compression is also enabled. For this reason, the ip rtp header-compression command appears in the output of the show running-config command. Since both TCP header compression and RTP header compression are enabled, both TCP packets and UDP packets are compressed.
The iphc-format keyword is not available for interfaces that use Frame Relay encapsulation.
Note
The ietf-format Keyword
The ietf-format keyword indicates that the IETF format of header compression will be used. For HDLC interfaces, the ietf-format keyword compresses only TCP packets. For PPP interfaces, when the ietf-format keyword is specified, RTP header compression is also enabled. For this reason, the ip rtp header-compression command appears in the output of the show running-config command. Since both TCP header compression and RTP header compression are enabled, both TCP packets and UDP packets are compressed.
The ietf-format keyword is not available for interfaces that use Frame Relay encapsulation.
Note
Examples
The following example sets the first serial interface for header compression with a maximum of ten cache entries:
Router> enableRouter# configure terminalRouter(config)# interface serial 0Router(config-if)# ip tcp header-compressionRouter(config-if)# ip tcp compression-connections 10Router(config-if)# endThe following example enables RTP header compression on the Serial1/0.0 subinterface and limits the number of RTP header compression connections to 10. In this example, the optional iphc-format keyword of the ip tcp header-compression command is specified.
Router> enableRouter# configure terminalRouter(config)# interface Serial1/0.0Router(config-if)# encapsulation pppRouter(config-if)# ip tcp header-compression iphc-formatRouter(config-if)# ip tcp compression-connections 10Router(config-if)# endThe following example enables RTP header compression on the Serial2/0.0 subinterface and limits the number of RTP header compression connections to 20. In this example, the optional ietf-format keyword of the ip tcp header-compression command is specified.
Router> enableRouter# configure terminalRouter(config)# interface Serial2/0.0Router(config-if)# encapsulation pppRouter(config-if)# ip tcp header-compression ietf-formatRouter(config-if)# ip tcp compression-connections 20Router(config-if)# endRelated Commands
ip tcp mss
To enable a maximum segment size (MSS) for TCP connections originating or terminating on a router, use the ip tcp mss command in global configuration mode. To disable the configuration of the MSS, use the no form of this command.
ip tcp mss bytes
no ip tcp mss bytes
Syntax Description
Defaults
This command is disabled.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
If this command is not enabled, the MSS value of 536 bytes is used if the destination is not on a LAN, otherwise the MSS value is 1460 for a local destination.
For connections originating from a router, the specified value is used directly as an MSS option in the synchronize (SYN) segment. For connections terminating on a router, the value is used only if the incoming SYN segment has an MSS option value higher than the configured value. Otherwise the incoming value is used as the MSS option in the SYN/acknowledge (ACK) segment.
Note
Examples
The following example sets the MSS value at 250:
ip tcp mss 250Related Commands
ip tcp header-compression
Specifies the total number of header compression connections that can exist on an interface.
ip tcp path-mtu-discovery
To enable the Path MTU Discovery feature for all new TCP connections from the router, use the ip tcp path-mtu-discovery command in global configuration mode. To disable the function, use the no form of this command.
ip tcp path-mtu-discovery [age-timer {minutes | infinite}]
no ip tcp path-mtu-discovery [age-timer {minutes | infinite}]
Syntax Description
Defaults
Disabled. If enabled, the minutes default is 10.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
Path MTU Discovery is a method for maximizing the use of available bandwidth in the network between the endpoints of a TCP connection. It is described in RFC 1191. Existing connections are not affected when this feature is turned on or off.
Customers using TCP connections to move bulk data between systems on distinct subnets would benefit most by enabling this feature.
The age timer is a time interval for how often TCP reestimates the path MTU with a larger MSS. When the age timer is used, TCP path MTU becomes a dynamic process. If the MSS used for the connection is smaller than what the peer connection can handle, a larger MSS is tried every time the age timer expires. The discovery process is stopped when either the send MSS is as large as the peer negotiated, or the user has disabled the timer on the router. You can turn off the age timer by setting it to infinite.
Examples
The following example enables Path MTU Discovery:
ip tcp path-mtu-discoveryip tcp queuemax
To alter the maximum TCP outgoing queue per connection, use the ip tcp queuemax command in global configuration mode. To restore the default value, use the no form of this command.
ip tcp queuemax packets
no ip tcp queuemax
Syntax Description
packets
Outgoing queue size of TCP packets. The default value is 5 segments if the connection has a TTY associated with it. If no TTY is associated with it, the default value is 20 segments.
Defaults
The default value is 5 segments if the connection has a TTY associated with it. If no TTY is associated with it, the default value is 20 segments.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
Changing the default value changes the 5 segments, not the 20 segments.
Examples
The following example sets the maximum TCP outgoing queue to 10 packets:
ip tcp queuemax 10ip tcp selective-ack
To enable TCP selective acknowledgment, use the ip tcp selective-ack command in global configuration mode. To disable TCP selective acknowledgment, use the no form of this command.
ip tcp selective-ack
no ip tcp selective-ack
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration (config)
Command History
Usage Guidelines
TCP might not experience optimal performance if multiple packets are lost from one window of data. With the limited information available from cumulative acknowledgments, a TCP sender can learn about only one lost packet per round-trip time. An aggressive sender could resend packets early, but such re-sent segments might have already been received.
The TCP selective acknowledgment mechanism helps overcome these limitations. The receiving TCP returns selective acknowledgment packets to the sender, informing the sender about data that has been received. The sender can then resend only the missing data segments.
TCP selective acknowledgment improves overall performance. The feature is used only when a multiple number of packets drop from a TCP window. There is no performance impact when the feature is enabled but not used.
This command becomes effective only on new TCP connections opened after the feature is enabled.
This feature must be disabled if you want TCP header compression. You might disable this feature if you have severe TCP problems.
Refer to RFC 2018 for more detailed information on TCP selective acknowledgment.
Examples
The following example enables the router to send and receive TCP selective acknowledgments:
ip tcp selective-ackRelated Commands
ip tcp synwait-time
To set a period of time the Cisco IOS software waits while attempting to establish a TCP connection before it times out, use the ip tcp synwait-time command in global configuration mode. To restore the default time, use the no form of this command.
ip tcp synwait-time seconds
no ip tcp synwait-time seconds
Syntax Description
seconds
Time (in seconds) the software waits while attempting to establish a TCP connection. It can be an integer from 5 to 300 seconds. The default is 30 seconds.
Defaults
The default time is 30 seconds.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
In versions previous to Cisco IOS software Release 10.0, the system would wait a fixed 30 seconds when attempting to establish a TCP connection. If your network contains public switched telephone network (PSTN) dial-on-demand routing (DDR), the call setup time may exceed 30 seconds. This amount of time is not sufficient in networks that have dialup asynchronous connections because it will affect your ability to Telnet over the link (from the router) if the link must be brought up. If you have this type of network, you may want to set this value to the UNIX value of 75.
Because this is a host parameter, it does not pertain to traffic going through the router, just for traffic originated at this device. Because UNIX has a fixed 75-second timeout, hosts are unlikely to experience this problem.
Examples
The following example configures the Cisco IOS software to continue attempting to establish a TCP connection for 180 seconds:
ip tcp synwait-time 180ip tcp timestamp
To enable TCP time stamp, use the ip tcp timestamp command in global configuration mode. To disable TCP time stamp, use the no form of this command.
ip tcp timestamp
no ip tcp timestamp
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration (config)
Command History
Usage Guidelines
TCP time stamp improves round-trip time estimates. Refer to RFC 1323 for more detailed information on TCP time stamp.
The TCP time stamp must be disabled if you want to use TCP header compression.
Examples
The following example enables the router to send TCP time stamps:
ip tcp timestampRelated Commands
ip tcp window-size
To alter the TCP window size, use the ip tcp window-size command in global configuration mode. To restore the default value, use the no form of this command.
ip tcp window-size bytes
no ip tcp window-size
Syntax Description
bytes
Window size (in bytes). An integer from 0 to 1073741823. The default value is 4128 bytes. Window scaling is enabled when the window size is greater than 65535 bytes.
Command Default
The default window size is 4128 bytes when window scaling is not enabled. If only one neighbor is configured for the window scaling extension, the default window size is 65535 bytes.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
Do not use this command unless you clearly understand why you want to change the default value.
To enable window scaling to support Long Fat Networks (LFNs), the TCP window size must be more than 65,535 bytes. The remote side of the link also needs to be configured to support window scaling. If both sides are not configured with window scaling, the default maximum value of 65,535 bytes is applied.
The scale factor is automatically calculated based on the window-size you configure. You cannot directly configure the scale factor.
Examples
The following example shows how to set the TCP window size to 1000 bytes:
ip tcp window-size 1000ip unreachables
To enable the generation of Internet Control Message Protocol (ICMP) unreachable messages, use the ip unreachables command in interface configuration mode. To disable this function, use the no form of this command.
ip unreachables
no ip unreachables
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
If the Cisco IOS software receives a nonbroadcast packet destined for itself that uses a protocol it does not recognize, it sends an ICMP unreachable message to the source.
If the software receives a datagram that it cannot deliver to its ultimate destination because it knows of no route to the destination address, it replies to the originator of that datagram with an ICMP host unreachable message.
This command affects all types of ICMP unreachable messages.
Examples
The following example enables the generation of ICMP unreachable messages, as appropriate, on an interface:
interface ethernet 0ip unreachablesip vrf
To define a VPN routing and forwarding (VRF) instance and to enter VRF configuration mode, use the ip vrf command in global configuration mode. To remove a VRF instance, use the no form of this command.
ip vrf vrf-name
no ip vrf vrf-name
Syntax Description
Command Default
No VRFs are defined. No import or export lists are associated with a VRF. No route maps are associated with a VRF.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
The ip vrf vrf-name command creates a VRF instance named vrf-name. To make the VRF functional, a route distinguisher (RD) must be created using the rd route-distinguisher command in VRF configuration mode. The rd route-distinguisher command creates the routing and forwarding tables and associates the RD with the VRF instance named vrf-name.
Examples
The following example shows how to import a route map to a VRF instance named VPN1:
ip vrf vpn1rd 100:2route-target both 100:2route-target import 100:1Related Commands
ip vrf (tracking)
To track an IP route in a specific VPN virtual routing and forwarding (VRF) table, use the ip vrf command in tracking configuration mode. To remove the tracking of the route, use the no form of this command.
ip vrf vrf-name
no ip vrf vrf-name
Syntax Description
Defaults
The tracking of a route is not configured.
Command Modes
Tracking configuration (config-track)
Command History
Usage Guidelines
This command is available for all IP-route tracked objects that are tracked by the track ip route global configuration command. Use this command to track a route that belongs to a specific VPN.
Examples
In the following example, the route associated with a VRF named VRF1 is tracked:
track 1 ip route 10.0.0.0 255.0.0.0 metric thresholdip vrf VRF1rd 100:1route-target both 100:1!interface e0/2no shutdownip vrf forwarding VRF1ip address 10.0.0.2 255.0.0.0Related Commands
ip vrf forwarding
Associates a VPN VRF with an interface or subinterface.
track ip route
Tracks the state of an IP route and enters tracking configuration mode.
ip wccp
To enable support of the specified Web Cache Communication Protocol (WCCP) service for participation in a service group, use the ip wccp command in global configuration mode. To disable the service group, use the no form of this command.
ip wccp {web-cache | service-number}[accelerated] [service-list service-access-list] [mode {open | closed}] [group-address multicast-address] [redirect-list access-list] [group-list access-list] [password [0-7] password]
no ip wccp {web-cache | service-number}[accelerated] [service-list service-access-list] [mode {open | closed}] [group-address multicast-address] [redirect-list access-list] [group-list access-list] [password [0-7] password]
Syntax Description
Command Default
WCCP services are not enabled on the router.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
WCCP transparent caching bypasses Network Address Translation (NAT) when fast (Cisco Express Forwarding [CEF]) switching is enabled. To work around this situation, WCCP transparent caching should be configured in the outgoing direction, fast/CEF switching should be enabled on the content engine interface, and the ip wccp web-cache redirect out command should be specified. Configure WCCP in the incoming direction on the inside interface by specifying the ip wccp redirect exclude in command on the router interface facing the cache. This configuration prevents the redirection of any packets arriving on that interface.
You can also include a redirect list when configuring a service group and the specified redirect list will deny packets with a NAT (source) IP address and prevent redirection. Refer to the ip wccp command for configuration of the redirect list and service group.
This command instructs a router to enable or disable the support for the specified service number or the web-cache service name. A service number can be from 0 to 254. Once the service number or name is enabled, the router can participate in the establishment of a service group.
When the no ip wccp command is entered, the router terminates participation in the service group, deallocates space if none of the interfaces still has the service configured, and terminates the WCCP task if no other services are configured.
The keywords following the web-cache keyword and the service-number argument are optional and may be specified in any order, but only may be specified once. The following sections outline the specific usage of each of the optional forms of this command.
ip wccp {web-cache | service-number} group-address multicast-address
A WCCP group address can be configured to set up a multicast address that cooperating routers and web caches can use to exchange WCCP protocol messages. If such an address is used, IP multicast routing must be enabled so that the messages that use the configured group (multicast) addresses are received correctly.
This option instructs the router to use the specified multicast IP address to coalesce the "I See You" responses for the "Here I Am" messages that it has received on this group address. The response is sent to the group address as well. The default is for no group address to be configured, in which case all "Here I Am" messages are responded to with a unicast reply.
ip wccp {web-cache | service-number} redirect-list access-list
This option instructs the router to use an access list to control the traffic that is redirected to the web caches of the service group specified by the service name given. The access-list argument specifies either a number from 1 to 99 to represent a standard access list number or a name to represent a named standard access list. The access list itself specifies which traffic is permitted to be redirected. The default is for no redirect list to be configured (all traffic is redirected).
WCCP requires that the following protocol and ports not be filtered by any access lists:
•
•
ip wccp {web-cache | service-number} group-list access-list
This option instructs the router to use an access list to control the web caches allowed to participate in the specified service group. The access-list argument specifies either a number from 1 to 99 to represent a standard access list number or a name to represent a named standard access list. The access list itself specifies which web caches are permitted to participate in the service group. The default is for no group list to be configured, in which case all web caches may participate in the service group.
Note
ip wccp {web-cache | service-number} password password
This option instructs the router to use MD5 authentication on the messages received from the service group specified by the service name given. Use this form of the command to set the password on the router. You must also configure the same password separately on each web cache. The password can be up to a maximum of eight characters. Messages that do not authenticate when authentication is enabled on the router are discarded. The default is for no authentication password to be configured and for authentication to be disabled.
ip wccp service-number service-list service-access-list mode closed
In applications where the interception and redirection of WCCP packet flows to external intermediate devices for the purpose of applying feature processing are not available within Cisco IOS software, it is necessary to block packet flows for the application when the intermediary device is not available. This blocking is called a closed service. By default, WCCP operates as an open service, wherein communication between clients and servers proceeds normally in the absence of an intermediary device. The service-list keyword can only be used for closed mode services. When a WCCP service is configured as closed, WCCP discards packets that do not have a client application registered to receive the traffic. Use the service-list keyword and service-access-list argument to register an application protocol type or port number.
When the definition of a service in a service list conflicts with the definition received via WCCP protocol, a warning message similar to the following is displayed:
Sep 28 14:06:35.923: %WCCP-5-SERVICEMISMATCH: Service 90 mismatched on WCCP client 10.1.1.13When there is a conflict in service list definitions, the configured definition takes precedence over the external definition received via WCCP protocol messages.
Examples
The following example shows how to configure a router to run WCCP reverse-proxy service, using the multicast address of 239.0.0.0:
ip multicast-routingip wccp 99 group-address 239.0.0.0interface ethernet 0ip wccp 99 group-listenThe following example shows how to configure a router to redirect web-related packets without a destination of 10.168.196.51 to the web cache:
access-list 100 deny ip any host 10.168.196.51access-list 100 permit ip any anyip wccp web-cache redirect-list 100interface ethernet 0ip wccp web-cache redirect outThe following example shows how to configure an access list to prevent traffic from network 10.0.0.0 leaving Fast Ethernet interface 0/0. Because the outbound ACL check is enabled, WCCP does not redirect that traffic. WCCP checks packets against the ACL before they are redirected.
ip wccp web-cacheip wccp check acl outboundinterface fastethernet0/0ip access-group 10 outip wccp web-cache redirect outaccess-list 10 deny 10.0.0.0 0.255.255.255access-list 10 permit anyIf the outbound ACL check is disabled, HTTP packets from network 10.0.0.0 would be redirected to a cache and users with that network address could retrieve web pages when the network administrator wanted to prevent this from happening.
The following example shows how to configure a closed WCCP service:
ip wccp 99 service-list access1 mode closedRelated Commands
ip wccp check acl outbound
To check the outbound access control list (ACL) for Web Cache Communication Protocol (WCCP), use the ip wccp check acl outbound command in global configuration mode. To disable the outbound check, use the no form of this command.
ip wccp check acl outbound
no ip wccp check acl outbound
Syntax Description
This command has no arguments or keywords.
Defaults
Check of the outbound ACL services is not enabled.
Command Modes
Global configuration (config)
Command History
Examples
The following example shows how to configure a router to run WCCP a check of outbound ACLs:
ip wccp check acl outboundRelated Commands
ip wccp check services all
To enable all Web Cache Communication Protocol (WCCP) services, use the ip wccp check services all command in global configuration mode. To disable all services, use the no form of this command.
ip wccp check services all
no ip wccp check services all
Syntax Description
This command has no arguments or keywords.
Defaults
WCCP services are not enabled on the router.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
With the ip wccp check services all command, WCCP can be configured to check all configured services for a match and perform redirection for those services if appropriate. The caches to which packets are redirected can be controlled by a redirect ACL as well as by the priority value of the service.
It is possble to configure an interface with more than one WCCP service. When more than one WCCP service is configured on an interface, the precedence of a service depends on the relative priority of the service compared to the priority of the other configured services. Each WCCP service has a priority value as part of its definition.
If no WCCP services are configured with a redirect ACL, the services are considered in priority order until a service is found which matches the IP packet. If no services match the packet, the packet is not redirected. If a service matches the packet and the service has a redirect ACL configured, then the IP packet will be checked against the ACL. If the packet is rejected by the ACL, the packet will not be passed down to lower priority services unless the ip wccp check servies all command is configured. When the ip wccp check services all command is configred, WCCP will continue to attempt to match the packet against any remaining lower priority services configured on the interface.
Note
Note
Examples
The following example shows how to configure all WCCP services:
ip wccp check services allRelated Commands
ip wccp enable
The ip wccp enable command has been replaced by the ip wccp command. See the description of the ip wccp command in this chapter for more information.
ip wccp group-listen
To configure an interface on a router to enable or disable the reception of IP multicast packets for Web Cache Communication Protocol (WCCP), use the ip wccp group-listen command in interface configuration mode. To disable the reception of IP multicast packets for WCCP, use the no form of this command.
ip wccp {web-cache | service number} group-listen
no ip wccp {web-cache | service number} group-listen
Syntax Description
web-cache
Directs the router to send packets to the web cache service.
service-number
WCCP service number; valid values are from 0 to 254.
Defaults
This command is disabled by default.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
Note
On Cisco 7600 series routers, the service-number may be either one of the provided standard keyword definitions or a number representing a cache engine dynamically defined definition. Once the service is enabled, the router can participate in the establishment of a service group.
On routers that are to be members of a Service Group when IP multicast is used, the following configuration is required:
•
•
•
Examples
The following example shows how to enable the multicast packets for a web cache with a multicast address of 224.1.1.100.
Router# configure terminalRouter(config)# ip multicast-routingRouter(config)# ip wccp web-cache group-address 224.1.1.100Router(config)# interface ethernet 0Router(config-if)# ip wccp web-cache group-listenRelated Commands
ip wccp
Directs a router to enable or disable the support for a WCCP cache engine service group.
ip wccp redirect
Enables WCCP redirection on an interface.
ip wccp redirect
To enable packet redirection on an outbound or inbound interface using Web Cache Communication Protocol (WCCP), use the ip wccp redirect command in interface configuration mode. To disable WCCP redirection, use the no form of this command.
ip wccp {web-cache | service-number} redirect {in | out}
no ip wccp {web-cache | service-number} redirect {in | out}
Syntax Description
Command Default
Redirection checking on the interface is disabled.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
WCCP transparent caching bypasses Network Address Translation (NAT) when fast (Cisco Express Forwarding [CEF]) switching is enabled. To work around this situation, WCCP transparent caching should be configured in the outgoing direction, fast/CEF switching enabled on the Content Engine interface, and the ip wccp web-cache redirect out command specified. Configure WCCP in the incoming direction on the inside interface by specifying the ip wccp redirect exclude in command on the router interface facing the cache. This prevents the redirection of any packets arriving on that interface.
You can also include a redirect list when configuring a service group and the specified redirect list will deny packets with a NAT (source) IP address and prevent redirection. Refer to the ip wccp command for configuration of the redirect list and service group.
The ip wccp redirect in command allows you to configure WCCP redirection on an interface receiving inbound network traffic. When the command is applied to an interface, all packets arriving at that interface will be compared against the criteria defined by the specified WCCP service. If the packets match the criteria, they will be redirected.
Likewise, the ip wccp redirect out command allows you to configure the WCCP redirection check at an outbound interface.
Tips
Note
Examples
In the following configuration, the multilink interface is configured to prevent the bypassing of NAT when fast/CEF switching is enabled:
Router(config)# interface multilink2Router(config-if)# ip address 10.21.21.1 255.255.255.0Router(config-if)# ip access-group IDS_Multilink2_in_1 inRouter(config-if)# ip wccp web-cache redirect outRouter(config-if)# ip nat outsideRouter(config-if)# ip inspect FSB-WALL outRouter(config-if)# max-reserved-bandwidth 100Router(config-if)# service-policy output fsb-policyRouter(config-if)# no ip route-cacheRouter(config-if)# load-interval 30Router(config-if)# tx-ring-limit 3Router(config-if)# tx-queue-limit 3Router(config-if)# ids-service-module monitoringRouter(config-if)# ppp multilinkRouter(config-if)# ppp multilink group 2Router(config-if)# crypto map abc1The following example shows how to configure a session in which reverse proxy packets on Ethernet interface 0 are being checked for redirection and redirected to a Cisco Cache Engine:
Router(config)# ip wccp 99Router(config)# interface ethernet 0Router(config-if)# ip wccp 99 redirect outThe following example shows how to configure a session in which HTTP traffic arriving on Ethernet interface 0/1 is redirected to a Cisco Cache Engine:
Router(config)# ip wccp web-cacheRouter(config)# interface ethernet 0/1Router(config-if)# ip wccp web-cache redirect inRelated Commands
ip wccp redirect exclude in
To configure an interface to exclude packets received on an interface from being checked for redirection, use the ip wccp redirect exclude in command in interface configuration mode. To disable the ability of a router to exclude packets from redirection checks, use the no form of this command.
ip wccp redirect exclude in
no ip wccp redirect exclude in
Syntax Description
This command has no arguments or keywords.
Defaults
Redirection exclusion is disabled.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
This configuration command instructs the interface to exclude inbound packets from any redirection check that may occur at the outbound interface. Note that the command is global to all the services and should be applied to any inbound interface that will be excluded from redirection.
This command is intended to be used to accelerate the flow of packets from a cache engine to the internet as well as allow for the use of the Web Cache Communication Protocol (WCCP) v2 packet return feature.
Examples
In the following example, packets arriving on Ethernet interface 0 are excluded from all WCCP redirection checks:
interface ethernet 0ip wccp redirect exclude inRelated Commands
ip wccp redirect-list
This command is now documented as part of the ip wccp command. See the description of the ip wccp command in this book for more information.
ip wccp version
To specify the version of Web Cache Communication Protocol (WCCP), use the ip wccp version command in global configuration mode.
ip wccp version {1 | 2}
Syntax Description
1
Web Cache Communication Protocol Version 1 (WCCPv1).
2
Web Cache Communication Protocol Version 2 (WCCPv2).
Defaults
WCCPv2
Command Modes
Global configuration (config)
Command History
Examples
In the following example, the user changes the WCCP version from the default of WCCPv2 to WCCPv1, starting in privileged EXEC mode:
Router(config)# ip wccp version 1Router# show ip wccp% WCCP version 2 is not enabledip wccp web-cache accelerated
To enable the hardware acceleration for WCCP version 1, use the ip wccp web-cache accelerated command in global configuration mode. To disable hardware acceleration, use the no form of this command.
ip wccp web-cache accelerated [[group-address group-address] | [redirect-list access-list] | [group-list access-list] | [password password]]
no ip wccp web-cache accelerated
Syntax Description
Defaults
Disabled
Command Modes
Global configuration (config)
Command History
Usage Guidelines
This command is supported on software releases later than cache engine software Release ACNS 4.2.1.
The group-address group-address option requires a multicast address that is used by the router to determine which cache engine should receive redirected messages. This option instructs the router to use the specified multicast IP address to coalesce the "I See You" responses for the "Here I Am" messages that it has received on this group address. In addition, the response is sent to the group address. The default is for no group-address to be configured, so that all "Here I Am" messages are responded to with a unicast reply.
The redirect-list access-list option instructs the router to use an access list to control the traffic that is redirected to the cache engines of the service group that is specified by the service-name given. The access-list argument specifies either a number from 1 to 99 to represent a standard or extended access-list number, or a name to represent a named standard or extended access list. The access list itself specifies the traffic that is permitted to be redirected. The default is for no redirect-list to be configured (all traffic is redirected).
The group-list access-list option instructs the router to use an access list to control the cache engines that are allowed to participate in the specified service group. The access-list argument specifies either a number from 1 to 99 to represent a standard access-list number, or a name to represent a named standard access list. The access list specifies which cache engines are permitted to participate in the service group. The default is for no group-list to be configured, so that all cache engines may participate in the service group.
The password can be up to seven characters. When you designate a password, the messages that are not accepted by the authentication are discarded. The password name is combined with the HMAC MD5 value to create security for the connection between the router and the cache engine.
Examples
The following example shows how to enable the hardware acceleration for WCCP version 1:
Router(config)# ip wccp web-cache acceleratedRelated Commands
kal-ap domain
To enable the IOS SLB KeepAlive Application Protocol (KAL-AP) agent to look for a domain tag when reporting the load for a virtual server, use the kal-ap domain command in server farm configuration mode. To delete the domain tag, use the no form of this command.
kal-ap domain tag
no kal-ap domain
Syntax Description
tag
1- to 64-character domain tag to be used by the KAL-AP agent. All characters are valid; case is significant.
Defaults
The KAL-AP agent does not look for a domain tag when reporting the load for a virtual server.
Command Modes
Server farm configuration (config-slb-sfarm)
Command History
Usage Guidelines
Configure the kal-ap domain command on the server farm that is associated with the virtual server for which the KAL-AP agent is to report the load.
Examples
The following example specifies that the KAL-AP agent is to look for domain tag chicago.com:
Router(config-slb-sfarm)# kal-ap domain chicago-comRelated Commands
