Cisco ASA 5500 Dual ISP Connection
Starting from version 7.2(1) and upwards, the Cisco ASA 5500 series firewall supports now the Dual-ISP capability. You can connect two interfaces of the firewall to two different ISPs and use the new “SLA Monitor” feature (SLA=Service Level Monitoring) to monitor the link to the primary ISP, and if that fails, the traffic is routed to the Backup ISP. The diagram below shows how to implement the Dual-ISP feature.
The configuration is shown below:
asa5500(config)# sla monitor 100
asa5500(config-sla-monitor)# type echo protocol ipIcmpEcho 100.100.100.2 interface outside
asa5500(config-sla-monitor-echo)# timeout 3000
asa5500(config-sla-monitor-echo)# frequency 10
asa5500(config)# sla monitor schedule 100 life forever start-time now
asa5500(config)# track 1 rtr 100 reachability
asa5500(config)# route outside 0.0.0.0 0.0.0.0 100.100.100.2 1 track 1
asa5500(config)# route backup-isp 0.0.0.0 0.0.0.0 200.200.200.2 254
Of course the configuration above assumes that you have already configured two interfaces connected to the ISPs, the first one with name ‘outside’ (security level 0) and the second one with name ‘backup-isp’ (security level 1).
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