Cisco Systems 78-11741-02 manual Defining VPNs, Enabling Hsrp, IPC-104

Configuring IP Services

Configuring the Hot Standby Router Protocol

Each VPN is associated with one or more VPN routing/forwarding (VRF) instances. A VRF consists of the following elements:

•IP routing table

•Cisco Express Forwarding (CEF) table

•Set of interfaces that use the CEF forwarding table

•Set of rules and routing protocol parameters to control the information in the routing tables

VPN routing information is stored in the IP routing table and the CEF table for each VRF. A separate set of routing and CEF tables is maintained for each VRF. These tables prevent information from being forwarded outside a VPN and also prevent packets that are outside a VPN from being forwarded to a router within the VPN.

HSRP currently adds ARP entries and IP hash table entries (aliases) using the default routing table instance. However, a different routing table instance is used when VRF forwarding is configured on an interface, causing ARP and ICMP echo requests for the HSRP virtual IP address to fail.

HSRP support for MPLS VPNs ensures that the HSRP virtual IP address is added to the correct IP routing table and not to the default routing table.

To configure this feature, perform the required tasks described in the following sections:

•Defining VPNs (Required)

•Enabling HSRP (Required)

Defining VPNs

To define VPNs, use the following commands on the PE routers beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# ip vrf vrf-name	Enters VRF configuration mode and assigns a
		VRF name.
Step 2
	Router(config-vrf)# rd route-distinguisher	Creates routing and forwarding tables.
Step 3
	Router(config-vrf)#route-target {import export	Creates a list of import or export route target
	both} route-target-ext-community	communities for the specified VRF.
Step 4	Router(config-vrf)# exit	Exits the current configuration mode and enters
		global configuration mode.
Step 5	Router(config)# interface type number	Specifies an interface and enters interface
		configuration mode.
Step 6
	Router(config-if)# ip vrf forwarding vrf-name	Associates a VRF with an interface or
		subinterface.

Enabling HSRP

To enable the HSRP on an interface, use the following command in interface configuration mode:

Command	Purpose
Router (config-if)# standby [group-number] ip ip-address	Enables the HSRP.

Cisco IOS IP Configuration Guide

IPC-104