This document provides a sample configuration for VPN load balancing on a Content Switching Module (CSM). VPN load balancing is a mechanism that intelligently distributes VPN sessions along a set of VPN concentrators or VPN head-end devices. VPN load balancing is implemented for these reasons:
to overcome performance or scalability limitations on VPN devices; for example, packets per second, connections per second, and throughput
to provide redundancy (remove a single point of failure)
Ensure that you meet these requirements before you attempt this configuration:
Implement Reverse Route Injection (RRI) at the head-end devices, to propagate the routing information from the spokes automatically.
Enable VLAN 61 and 51 to share the same subnet.
The information in this document is based on these software and hardware versions:
Cisco Catalyst 6500 with CSM
Cisco 2621 Router
Cisco 7206
Cisco 7206VXR
Cisco 7204VXR
Cisco 7140
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Refer to Cisco Technical Tips Conventions for more information on document conventions.
In this section, you are presented with the information to configure the features described in this document.
Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.
This document uses this network setup:
This document uses these configurations:
Complete these steps:
Implement RRI at the head-end devices, to propagate the routing information from the spokes automatically.
Note: VLAN 61 and VLAN 51 share the same subnet.
Define the VLAN client and the VLAN server.
Define the probe used to check the health of the IPSec servers.
!--- The CSM is located in slot 4. module ContentSwitchingModule 4 vlan 51 client ip address 172.21.51.244 255.255.255.240 ! vlan 61 server ip address 172.21.51.244 255.255.255.240 ! probe ICMP_PROBE icmp interval 5 retries 2 !
Define the serverfarm with the real IPSec servers.
Configure failaction purge, to flush the connections that belong to dead servers.
Define the sticky policy.
!--- Serverfarm VPN_IOS and real server members. serverfarm VPN_IOS nat server no nat client !--- Set the behavior of connections when the real servers have failed. failaction purge real 172.21.51.242 inservice real 172.21.51.247 inservice probe ICMP_PROBE ! !--- Ensure that connections from the same client match the same server !--- load balancing (SLB) policy. !--- Use the same real server on subsequent connections; issue the !--- sticky command. sticky 5 netmask 255.255.255.255 timeout 60 ! policy VPNIOS sticky-group 5 serverfarm VPN_IOS !
Define VServers, one per traffic flow.
!--- Virtual server VPN_IOS_ESP. vserver VPN_IOS_ESP !--- The virtual server IP address is specified. virtual 172.21.51.253 50 !--- Persistence rebalance is used for HTTP 1.1, to rebalance the connection !--- to a new server using the load balancing policy. persistent rebalance !--- Associate the load balancing policy with the VPNIOS virtual server. slb-policy VPNIOS inservice ! vserver VPN_IOS_IKE virtual 172.21.51.253 udp 500 persistent rebalance slb-policy VPNIOS inservice !
crypto isakmp policy 10 authentication pre-share crypto isakmp key cisco123 address 0.0.0.0 ! crypto ipsec transform-set myset esp-3des esp-sha-hmac crypto mib ipsec flowmib history tunnel size 200 crypto mib ipsec flowmib history failure size 200 ! crypto dynamic-map mydyn 10 set transform-set myset reverse-route ! crypto map mymap 10 ipsec-isakmp dynamic mydyn ! interface FastEthernet0/0 ip address 172.21.51.247 255.255.255.240 crypto map mymap ! interface FastEthernet2/0 ip address 10.1.1.6 255.255.255.0 router eigrp 1 redistribute static network 10.0.0.0 no auto-summary no eigrp log-neighbor-changes ! ip default-gateway 172.21.51.241 ip classless ip route 0.0.0.0 0.0.0.0 172.21.51.241 no ip http server !
crypto isakmp policy 10 authentication pre-share crypto isakmp key cisco123 address 172.21.51.253 ! crypto ipsec transform-set myset esp-3des esp-sha-hmac crypto mib ipsec flowmib history tunnel size 200 crypto mib ipsec flowmib history failure size 200 ! crypto map mymap 10 ipsec-isakmp set peer 172.21.51.253 set transform-set myset match address 101 ! interface Loopback0 ip address 10.3.3.3 255.255.255.0 ! interface Ethernet0/0 ip address 172.21.51.250 255.255.255.240 duplex auto crypto map mymap ! ip classless ip route 0.0.0.0 0.0.0.0 172.21.51.241 no ip http server ! access-list 101 permit ip 10.3.3.0 0.0.0.255 10.1.1.0 0.0.0.255 !
Use this section to confirm that your configuration works properly.
The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
Issue the show module csm all or show module contentSwitchingModule all command; both commands generate the same information.
The show module contentSwitchingModule all vservers command shows the SLB virtual server information.
Cat6506-1-Native# show module contentSwitchingModule all vservers ---------------------- CSM in slot 4 ---------------------- slb vserver prot virtual vlan state conns --------------------------------------------------------------------------- VPN_IOS_ESP 50 172.21.51.253/32:0 ALL OPERATIONAL 2 VPN_IOS_IKE UDP 172.21.51.253/32:500 ALL OPERATIONAL 2
The show module contentSwitchingModule all conns command shows SLB connection information.
Cat6506-1-Native# show module contentSwitchingModule all conns ---------------------- CSM in slot 4 ---------------------- prot vlan source destination state ---------------------------------------------------------------------- In UDP 51 172.21.51.250:500 172.21.51.253:500 ESTAB Out UDP 61 172.21.51.242:500 172.21.51.250:500 ESTAB In 50 51 172.21.51.251 172.21.51.253 ESTAB Out 50 61 172.21.51.247 172.21.51.251 ESTAB In 50 51 172.21.51.250 172.21.51.253 ESTAB Out 50 61 172.21.51.242 172.21.51.250 ESTAB In UDP 51 172.21.51.251:500 172.21.51.253:500 ESTAB Out UDP 61 172.21.51.247:500 172.21.51.251:500 ESTAB
The show module contentSwitchingModule all sticky command shows the SLB sticky database.
Cat6506-1-Native# show module contentSwitchingModule all sticky ---------------------- CSM in slot 4 ---------------------- client IP: 172.21.51.250 real server: 172.21.51.242 connections: 0 group id: 5 timeout: 38 sticky type: netmask 255.255.255.255 client IP: 172.21.51.251 real server: 172.21.51.247 connections: 0 group id: 5 timeout: 40 sticky type: netmask 255.255.255.255
Issue the show ip route command on the router.
2621VPN# show ip route !--- Output suppressed. 10.0.0.0/24 is subnetted, 3 subnets D EX 10.2.2.0 [170/30720] via 10.1.1.6, 00:13:57, FastEthernet0/0 D EX 10.3.3.0 [170/30720] via 10.1.1.5, 00:16:15, FastEthernet0/0 C 10.1.1.0 is directly connected, FastEthernet0/0 D*EX 0.0.0.0/0 [170/30720] via 10.1.1.5, 00:37:58, FastEthernet0/0 [170/30720] via 10.1.1.6, 00:37:58, FastEthernet0/0 2621VPN# 7206VXR# show ip route !--- Output suppressed. 172.21.0.0/28 is subnetted, 1 subnets C 172.21.51.240 is directly connected, FastEthernet0/0 10.0.0.0/24 is subnetted, 3 subnets S 10.2.2.0 [1/0] via 0.0.0.0, FastEthernet0/0 D EX 10.3.3.0 [170/30720] via 10.1.1.5, 00:16:45, FastEthernet2/0 C 10.1.1.0 is directly connected, FastEthernet2/0 S* 0.0.0.0/0 [1/0] via 172.21.51.241
There is currently no specific troubleshooting information available for this configuration.