Cisco 7600 Series Router Software Configuration Guide, Cisco IOS Release 15S

WCCP Overview

The Web Cache Communication Protocol (WCCP) is a Cisco-developed content-routing technology that allows you to integrate cache engines (such as the Cisco Cache Engine 550) into your network infrastructure.

Note Cisco Systems replaced the Cache Engine 500 Series platforms with Content Engine Platforms in July 2001. Cache Engine Products were the Cache Engine 505, 550, 570, and 550-DS3. Content Engine Products are the Content Engine 507, 560, 590, and 7320.

The Cisco IOS WCCP feature allows use of Cisco Cache Engines (or other caches running WCCP) to localize web traffic patterns in the network, enabling content requests to be fulfilled locally. Traffic localization reduces transmission costs and download time.

WCCP enables Cisco IOS routing platforms to transparently redirect content requests. The main benefit of transparent redirection is that users need not configure their browsers to use a web proxy. Instead, they can use the target URL to request content, and have their requests automatically redirected to a cache engine. The word “transparent” is this case means that the end user does not know that a requested file (such as a web page) came from the cache engine instead of from the originally specified server.

When a cache engine receives a request, it attempts to service it from its own local cache. If the requested information is not present, the cache engine issues its own request to the originally targeted server to get the required information. When the cache engine retrieves the requested information, it forwards it to the requesting client and caches it to fulfill future requests, thus maximizing download performance and substantially reducing transmission costs.

WCCP enables a series of cache engines, called a cache engine cluster, to provide content to a router or multiple routers. Network administrators can easily scale their cache engines to handle heavy traffic loads through these clustering capabilities. Cisco clustering technology enables each cache member to work in parallel, resulting in linear scalability. Clustering cache engines greatly improves the scalability, redundancy, and availability of your caching solution. You can cluster up to 32 cache engines to scale to your desired capacity.

Hardware Acceleration

Cisco 7600 series routers provide WCCP Layer 2 PFC redirection hardware acceleration for directly connected Cisco Cache Engines, which is more efficient than Layer 3 redirection in software on the MSFC with generic route encapsulation (GRE).

WCCP Layer 2 PFC redirection allows Cisco Cache Engines to use hardware-supported Layer 2 redirection. A directly connected Cache Engine can be configured to negotiate use of the WCCP Layer 2 PFC Redirection feature. The WCCP Layer 2 PFC redirection feature requires no configuration on the MSFC. The show ip wccp web-cache detail command displays which redirection method is in use for each cache.

The following guidelines apply to WCCP Layer 2 PFC redirection:

• The WCCP Layer 2 PFC redirection feature sets the IP flow mask to full-flow mode.
• You can configure the Cisco Cache Engine software release 2.2 or later releases to use the WCCP Layer 2 PFC redirection feature.
• Layer 2 redirection takes place on the PFC and is not visible to the MSFC. The show ip wccp web-cache detail command on the MSFC displays statistics for only the first packet of a Layer 2 redirected flow, which provides an indication of how many flows, rather than packets, are using Layer 2 redirection. Entering the show mls entries command displays the other packets in the Layer 2 redirected flows.

Note ● The PFC provides hardware acceleration for generic route encapsulation (GRE). If you use WCCP Layer 3 redirection with generic route encapsulation (GRE), there is hardware support for encapsulation, but the PFC3 does not provide hardware support for decapsulation of WCCP GRE traffic.

• Releases of Cisco Application and Content Networking System (ACNS) software later than Release 4.2.1 support the accelerated keyword.

Understanding WCCPv1 Configuration

With WCCP-Version 1, only a single router services a cluster. In this scenario, this router is the device that performs all the IP packet redirection. Figure 60-1 illustrates how this configuration appears.

Figure 60-1 Cisco Cache Engine Network Configuration Using WCCP-Version 1

Content is not duplicated on the cache engines. The benefit of using multiple caches is that you can scale a caching solution by clustering multiple physical caches to appear as one logical cache.

The following sequence of events details how WCCPv1 configuration works:

1. Each cache engine is configured by the system administrator with the IP address of the control router. Up to 32 cache engines can connect to a single control router.

2. The cache engines send their IP addresses to the control router using WCCP, indicating their presence. Routers and cache engines communicate to each other via a control channel; this channel is based on UDP port 2048.

3. This information is used by the control router to create a cluster view (a list of caches in the cluster). This view is sent to each cache in the cluster, essentially making all the cache engines aware of each other. A stable view is established after the membership of the cluster remains the same for a certain amount of time.

4. Once a stable view has been established, one cache engine is elected as the lead cache engine. (The lead is defined as the cache engine seen by all the cache engines in the cluster with the lowest IP address). This lead cache engine uses WCCP to indicate to the control router how IP packet redirection should be performed. Specifically, the lead cache engine designates how redirected traffic should be distributed across the cache engines in the cluster.

Understanding WCCPv2 Configuration

Multiple routers can use WCCPv2 to service a cache cluster. This is in contrast to WCCPv1 in which only one router could redirect content requests to a cluster. Figure 60-2 illustrates a sample configuration using multiple routers.

Figure 60-2 Cisco Cache Engine Network Configuration Using WCCP v2

The subset of cache engines within a cluster and routers connected to the cluster that are running the same service is known as a service group. Available services include TCP and User Datagram Protocol (UDP) redirection.

Using WCCPv1, the cache engines were configured with the address of the single router. WCCPv2 requires that each cache engine be aware of all the routers in the service group. To specify the addresses of all the routers in a service group, you must choose one of the following methods:

• Unicast—A list of router addresses for each of the routers in the group is configured on each cache engine. In this case the address of each router in the group must be explicitly specified for each cache engine during configuration.
• Multicast—A single multicast address is configured on each cache engine. In the multicast address method, the cache engine sends a single-address notification that provides coverage for all routers in the service group. For example, a cache engine could indicate that packets should be sent to a multicast address of 224.0.0.100, which would send a multicast packet to all routers in the service group configured for group listening using WCCP (see the ip wccp group-listen interface configuration command for details).

The multicast option is easier to configure because you need only specify a single address on each cache engine. This option also allows you to add and remove routers from a service group dynamically, without needing to reconfigure the cache engines with a different list of addresses each time.

The following sequence of events details how WCCPv2 configuration works:

1. Each cache engine is configured with a list of routers.

2. Each cache engine announces its presence and a list of all routers with which it has established communications. The routers reply with their view (list) of cache engines in the group.

3. Once the view is consistent across all cache engines in the cluster, one cache engine is designated as the lead and sets the policy that the routers need to deploy in redirecting packets.

The following sections describe how to configure WCCPv2 on routers so they may participate in a service group.

WCCPv2 Features

These sections describe WCCPv2 features:

• Support for Non-HTTP Services
• Support for Multiple Routers
• MD5 Security
• Web Cache Packet Return
• Load Distribution

Support for Non-HTTP Services

WCCPv2 allows redirection of traffic other than HTTP (TCP port 80 traffic), including a variety of UDP and TCP traffic. WCCPv1 supported the redirection of HTTP (TCP port 80) traffic only. WCCPv2 supports the redirection of packets intended for other ports, including those used for proxy-web cache handling, File Transfer Protocol (FTP) caching, FTP proxy handling, web caching for ports other than 80, and real audio, video, and telephony applications.

To accommodate the various types of services available, WCCPv2 introduces the concept of multiple service groups. Service information is specified in the WCCP configuration commands using dynamic services identification numbers (such as “98”) or a predefined service keywords (such as “web-cache”). This information is used to validate that service group members are all using or providing the same service.

The cache engines in service group specify traffic to be redirected by protocol (TCP or UDP) and port (source or destination). Each service group has a priority status assigned to it. Packets are matched against service groups in priority order.

Support for Multiple Routers

WCCPv2 allows multiple routers to be attached to a cluster of cache engines. The use of multiple routers in a service group allows for redundancy, interface aggregation, and distribution of the redirection load.

MD5 Security

WCCPv2 provides optional authentication that enables you to control which routers and cache engines become part of the service group using passwords and the HMAC MD5 standard. Shared-secret MD5 one-time authentication (set using the ip wccp [ password [ 0-7 ] password ] global configuration command) enables messages to be protected against interception, inspection, and replay.

Web Cache Packet Return

If a cache engine is unable to provide a requested object it has cached due to error or overload, the cache engine will return the request to the router for onward transmission to the originally specified destination server. WCCPv2 provides a check on packets that determines which requests have been returned from the cache engine unserviced. Using this information, the router can then forward the request to the originally targeted server (rather than attempting to resend the request to the cache cluster). This provides error handling transparency to clients.

Typical reasons why a cache engine would reject packets and initiate the packet return feature include the following:

• Instances when the cache engine is overloaded and has no room to service the packets
• Instances when the cache engine is filtering for certain conditions that make caching packets counterproductive (for example, when IP authentication has been turned on)

Load Distribution

WCCPv2 can be used to adjust the load being offered to individual cache engines to provide an effective use of the available resources while helping to ensure high quality of service (QoS) to the clients. WCCPv2 allows the designated cache to adjust the load on a particular cache and balance the load across the caches in a cluster. WCCPv2 uses three techniques to perform load distribution:

• Hot Spot Handling—Allows an individual hash bucket to be distributed across all the cache engines. Prior to WCCPv2, information from one hash bucket could only go to one cache engine.
• Load Balancing—Allows the set of hash buckets assigned to a cache engine to be adjusted so that the load can be shifted from an overwhelmed cache engine to other members that have available capacity.
• Load Shedding—Enables the router to selectively redirect the load to avoid exceeding the capacity of a cache engine.

By using these hashing parameters, you can prevent one cache from being overloaded and reduce the potential for congestion.

Specifying a Version of WCCP

Until you configure a WCCP service using the ip wccp { web-cache | service-number } global configuration command, WCCP is disabled on the router. The first use of a form of the ip wccp command enables WCCP. By default WCCPv2 is used for services, but you can use WCCPv1 functionality instead. To change the running version of WCCP from Version 2 to Version 1, or to return to WCCPv2 after an initial change, perform this task in EXEC mode:

WCCPv1 does not use the WCCP commands from earlier Cisco IOS versions. Instead, use the WCCP commands documented in this chapter. If a function is not allowed in WCCPv1, an error prompt will be printed to the screen. For example, if WCCPv1 is running on the router and you try to configure a dynamic service, the following message will be displayed: “WCCP V1 only supports the web-cache service.” The show ip wccp EXEC command will display the WCCP protocol version number that is currently running on your router.

Configuring a Service Group Using WCCPv2

WCCPv2 uses service groups based on logical redirection services, deployed for intercepting and redirecting traffic. The standard service is web cache, which intercepts TCP port 80 (HTTP) traffic and redirects that traffic to the cache engines. This service is referred to as a well-known service, because the characteristics of the web cache service are known by both the router and cache engines. A description of a well-known service is not required beyond a service identification (in this case, the command line interface (CLI) provides a web-cache keyword in the command syntax).

In addition to the web cache service, there can be up to seven dynamic services running concurrently in a service group.

Note More than one service can run on a router at the same time, and routers and cache devices can be part of multiple service groups at the same time.

The dynamic services are defined by the cache engines; the cache instructs the router which protocol or ports to intercept, and how to distribute the traffic. The router itself does not have information on the characteristics of the dynamic service group’s traffic, because this information is provided by the first web cache to join the group. In a dynamic service, up to eight ports can be specified within a single protocol.

Cisco Cache Engines, for example, use dynamic service 99 to specify a reverse-proxy service. However, other cache devices may use this service number for some other service. The following configuration information deals with enabling general services on Cisco routers. Refer to the cache server documentation for information on configuring services on cache devices.

To enable a service on a Cisco 7600 series router, perform this task:

Note A future release of Cisco Application and Content Networking System (ACNS) software (Release 4.2.2 or later) supports the ip wccp service accelerated command.

As indicated by the out and in keyword options in the ip wccp service redirect command, redirection can be specified for outbound interfaces or inbound interfaces.

Inbound traffic can be configured to use Cisco Express Forwarding (CEF), distributed Cisco Express Forwarding (dCEF), Fast Forwarding, or Process Forwarding.

Configuring WCCP for redirection for inbound traffic on interfaces allows you to avoid the overhead associated with CEF forwarding for outbound traffic. Setting an output feature on any interface results in the slower switching path of the feature being taken by all packets arriving at all interfaces. Setting an input feature on an interface results in only those packets arriving at that interface taking the configured feature path; packets arriving at other interfaces will use the faster default path. Configuring WCCP for inbound traffic also allows packets to be classified before the routing table lookup, which provides faster redirection of packets.

Specifying a Web Cache Service

To configure a web-cache service, perform this task:

Excluding Traffic on a Specific Interface from Redirection

To exclude any interface from redirecting inbound traffic, perform this task in global configuration mode:

Registering a Router to a Multicast Address

If you decide to use the multicast address option for your service group, you must configure the router to listen for the multicast broadcasts on an interface. To configure the router, perform this task:

For network configurations where redirected traffic needs to traverse an intervening router, the router being traversed must be configured to perform IP multicast routing. You must configure the following two components to enable traversal over an intervening router:

• Enable IP multicast routing using the ip multicast routing interface configuration command.
• Enable the interfaces to which the cache engines will connect to receive multicast transmissions using the ip wccp group-listen interface configuration command (note that earlier Cisco IOS versions required the use of the ip pim interface configuration command).

Using Access Lists for a WCCP Service Group

To configure the router to use an access list to determine which traffic should be directed to which cache engines, perform this task in global configuration mode:

To disable caching for certain clients, perform this task in global configuration mode:

Setting a Password for a Router and Cache Engines

MD5 password security requires that each router and cache engine that wants to join a service group be configured with the service group password. The password can consist of up to seven characters. Each cache engine or router in the service group will authenticate the security component in a received WCCP packet immediately after validating the WCCP message header. Packets failing authentication will be discarded.

To configure an MD5 password for use by the router in WCCP communications, perform this task in global configuration mode:

Changing the Version of WCCP on a Router Example

The following example shows the process of changing the WCCP version from the default of WCCPv2 to WCCPv1, and enabling the web-cache service in WCCPv1:

Performing a General WCCPv2 Configuration Example

The following example shows a general WCCPv2 configuration session:

Running a Web Cache Service Example

The following example shows a web cache service configuration session:

The following example shows a configuration session in which redirection of HTTP traffic arriving on VLAN interface 30 is enabled:

Running a Reverse Proxy Service Example

The following example assumes you a configuring a service group using Cisco Cache Engines, which use dynamic service 99 to run a reverse proxy service:

Registering a Router to a Multicast Address Example

The following example shows how to register a router to a multicast address of 224.1.1.100:

The following example shows a router configured to run a reverse proxy service, using the multicast address of 224.1.1.1. Redirection applies to packets outgoing through VLAN interface 60:

Using Access Lists Example

To achieve better security, you can use a standard access list to notify the router which IP addresses are valid addresses for a cache engine attempting to register with the current router. The following example shows a standard access list configuration session where the access list number is 10 for some sample hosts:

To disable caching for certain clients, servers, or client/server pairs, you can use WCCP access lists. The following example shows that any requests coming from 10.1.1.1 to 12.1.1.1 will bypass the cache and that all other requests will be serviced normally:

The following example configures a router to redirect web-related packets received through VLAN interface 70, destined to any host except 209.165.196.51:

Setting a Password for a Router and Cache Engines Example

The following example shows a WCCPv2 password configuration session where the password is alaska1:

Verifying WCCP Settings Example

To verify your configuration changes, use the more system:running-config EXEC command. The following example shows that the both the web cache service and dynamic service 99 are enabled on the router:

Configuring VRF Support on WCCP

Complete these steps to configure VRF support on WCCP.

Summary Steps

1. enable

2. configure terminal

3. ip vrf vrf-name

4. rd route-distinguisher

5. exit

6. ip wccp [vrf vrf-name ] {web-cache | service-number | source-interface source-interface } [group-address group-address ] [redirect-list access-list ] [group-list access-list ] [password password ]

7. interface type number

8. ip vrf forwarding vrf-name

9. ip address ip-address subnet-mask

10. ip wccp [vrf vrf-name ] {web-cache | service-number} redirect {out | in}

11. end

Detailed Steps

Examples

This example shows how to configure a web-cache service on an interface with VRF.

This example shows how to configure a web-cache service on an interface with VRF and ACL configured.

Verification

Use the show ip wccp summary command to display the summary of all WCCP services including VRF specific WCCP configuration.

Use the show ip wccp vrf vrf-id command to display the VRF specific WCCP configuration.

Troubleshooting Tips

Restrictions and Usage Guidelines

Following restrictions apply while configuring WCCPv2 IPv6 feature on the Cisco 7600 series routers.

• Supports only these WCCP features:

– Layer 2 redirection

– Layer 2 return

– Mask assignment

• VRF is not supported.
• Redirection is supported only in the ingress direction and egress redirection is not supported.
• Hash assignment is not supported.
• GRE redirection and return are not supported.
• These WCCP commands are disabled for the WCCPv2 IPv6 feature:

– ipv6 wccp check acl outbound

– ipv6 wccp check services all

– ip wccp redirect exclude in

Configuring WCCPv2 IPv6 Support

Complete these steps to configure WCCPv2 IPv6 support on Cisco 7600 routers.

Summary Steps

1. enable

2. configure terminal

3. ipv6 wccp {web-cache | service-number | source-interface source-interface } [group-address group-address ] [redirect-list access-list ] [group-list access-list ] [password password ]

4. ipv6 unicast-routing

5. mls ipv6 acl compress address unicast

6. interface type number

7. ipv6 enable

8. ipv6 address ipv6-address/prefix

9. ipv6 wccp {web-cache | service-number } redirect in

10. end

Detailed Steps

Examples

This example shows how to configure web-cache service on an interface with IPv6 address.

Router(config)# ipv6 unicast-routing

Verification

Use these commands to verify the WCCPv2 IPv6 support feature.

This is a sample output of the show ipv6 wccp capabilities command.

Troubleshooting Tips