Configuring WCCP: Cisco WCCP User & Service Manual PDF

Restrictions for WCCP

Configuring WCCP This section provides information about configuring WCCP. Prerequisites for WCCP, on page 1 Restrictions for WCCP, on page 1 Information About WCCP, on page 3 How to Configure WCCP, on page 9 Configuration Examples for WCCP, on page 16 Feature History for WCCP, on page 21 Prerequisites for WCCP • To use WCCP, IP must be configured on the interface connected to the Internet and another interface must be connected to the content engine. • The interface connected to the content engine must be a Fast Ethernet or Gigabit Ethernet interface. Restrictions for WCCP General The following limitations apply to Web Cache Communication Protocol Version 2 (WCCPv2):

• WCCP works only with IPv4 networks. • WCCP bypasses Network Address Translation (NAT) when Cisco Express Forwarding is enabled. • WCCP does not interoperate with NAT and the zone-based firewall configured together in a network. • Service groups can comprise up to 32 content engines and 32 switches. • For switches servicing a multicast cluster, the Time To Live (TTL) value must be set at 15 or fewer. • All content engines in a cluster must be configured to communicate with all devices servicing the cluster. • Multicast addresses must be from 224.0.0.0 to 239.255.255.255. Configuring WCCP 1

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Restrictions for WCCP

• Up to eight service groups are supported at the same time on the same client interface. • The Layer 2 rewrite forwarding method is supported; but generic routing encapsulation (GRE) is not. • Direct Layer 2 connectivity to content engines is required when Layer 2 mode is deployed; Layer 3 connectivity of one or more hops away is not supported. • Ternary content addressable memory (TCAM) friendly mask-based assignment is supported, but the hash bucket-based method is not. • When the TCAM space is exhausted, traffic is not redirected but is forwarded normally. • The WCCP version 2 standard allows for support of up to 256 distinct masks.

However, a Cisco Catalyst 9000 series switch supports only mask assignment tables with a single mask. • A content engine configured for mask assignment that tries to join a farm where the selected assignment method is hash remains out of the farm as long as the cache engine assignment method does not match that of the existing farm. • WCCP redirection is not supported on Multiprotocol Label Switching (MPLS) and port-channel interfaces. • WCCP high availability is not supported in modular, stacking, and StackWise Virtual (SVL) mode. • The packets redirected counter in the output of the command show ip wccp detail only increments whenever a packet is redirected via CPU switching.

Whenever Cisco Express Forwarding (CEF) is being used with inbound WCCP redirection, L2 forwarding method, and mask assignment, all WCCP traffic should be redirected via hardware. When traffic is redirected via hardware the counters will not increment. Catalyst 9000 Series Switches Access Control Lists When WCCP is using the mask assignment, any redirect list is merged with the mask information from the appliance and the resulting merged ACL is passed down to the Catalyst 9000 series switch hardware. Only Permit or Deny ACL entries from the redirect list in which the protocol is IP or exactly matches the service group protocol are merged with the mask information from the appliance.

The following restrictions apply to the redirect-list ACL: • The ACL must be an IPv4 extended ACL. • Only individual source or destination port numbers may be specified; port ranges cannot be specified. • The only valid matching criteria in addition to individual source or destination port numbers are dscp or tos . • The use of fragments , time-range , or options keywords, or any TCP flags is not permitted. • If the redirect ACL does not meet the restrictions shown, the system will log the following error message: WCCP-3-BADACE: Service group>, invalid access-list entry (seq: , reason: ) Configuring WCCP Restrictions for WCCP Configuring WCCP 2

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WCCPv2 Configuration

Information About WCCP The Web Cache Communication Protocol (WCCP) is a Cisco-developed content-routing technology that intercepts IP packets and redirects those packets to a destination other than the one specified in the IP packet. Typically the packets are redirected from their destination web server on the Internet to a content engine that is local to the client. In some WCCP deployment scenarios, redirection of traffic may also be required from the web server to the client. WCCP enables you to integrate content engines into your network infrastructure. The tasks in this document assume that you have already configured content engines on your network.

WCCP Overview WCCP uses Cisco Content Engines (or other content engines running WCCP) to localize traffic patterns in the network, enabling content requests to be fulfilled locally. Traffic localization reduces transmission costs and download time. WCCP enables Cisco IOS XE platforms to transparently redirect content requests. With transparent redirection, users can fulfill content requests locally without configuring 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 content engine.

The word "transparent" in this case means that the end user does not know that a requested file (such as a web page) came from the content engine instead of from the originally specified server. A content engine receiving a request attempts to service it from its own local cache. If the requested information is not present, the content engine issues its own request to the originally targeted server to get the required information. A content engine retrieving the requested information 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 content engines, called a content engine cluster, to provide content to a device or multiple devices. Network administrators can easily scale their content engines to manage heavy traffic loads through these clustering capabilities. Cisco clustering technology enables each cluster member to work in parallel, resulting in linear scalability. Clustering content engines greatly improves the scalability, redundancy, and availability of your caching solution. You can cluster up to 32 content engines to scale to your desired capacity.

WCCP Mask Assignment The WCCP Mask Assignment feature enables mask assignment as the load-balancing method (instead of the default hash assignment method) for a WCCP service. For content engines running Application and Content Networking System (ACNS) software, use the wccp custom-web-cache command with the mask-assign keyword to configure mask assignment. For content engines running Cisco Wide Area Application Services (WAAS) software, use the wccp tcp-promiscuous command with the mask-assign keyword to configure mask assignment. WCCPv2 Configuration Multiple devices can use WCCPv2 to service a content engine cluster.

The figure below illustrates a sample configuration using multiple devices. Configuring WCCP Information About WCCP Configuring WCCP 3

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WCCPv2 Configuration

Figure 1: Cisco Content Engine Network Configuration Using WCCPv2 The subset of content engines within a cluster and devices connected to the cluster that are running the same service is known as a service group. Available services include TCP and UDP redirection. WCCPv2 requires that each content engine be aware of all the devices in the service group. To specify the addresses of all the devices in a service group, choose one of the following methods: • Unicast—A list of device addresses for each of the devices in the group is configured on each content engine. In this case, the address of each device in the group must be explicitly specified for each content engine during configuration.

• Multicast—A single multicast address is configured on each content engine. In the multicast address method, the content engine sends a single-address notification that provides coverage for all switches in the service group. For example, a content 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 devices 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 content engine.

This option also allows you to add and remove routers from a service group dynamically, without needing to reconfigure the content engines with a different list of addresses each time. The following sequence of events details how WCCPv2 configuration works: 1. Each content engine is configured with a list of devices. 2. Each content engine announces its presence and a list of all devices with which it has established communications. The routers reply with their view (list) of content engines in the group. 3.

When the view is consistent across all content engines in the cluster, one content engine is designated as the lead and sets the policy that the devices need to deploy in redirecting packets. Configuring WCCP WCCPv2 Configuration Configuring WCCP 4

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