In this article, we will explore the concept of Policy-Based Routing (PBR) with ISP failover, a critical technique for ensuring network reliability and efficient traffic management. Below, we provide verified commands and configurations to implement this setup effectively.
Key Steps and Commands
1. NAT Translation
Configure NAT to translate internal IP addresses to public IPs for outbound traffic.
interface GigabitEthernet0/1 ip nat inside interface GigabitEthernet0/2 ip nat outside access-list 1 permit 192.168.1.0 0.0.0.255 ip nat inside source list 1 interface GigabitEthernet0/2 overload
2. Reliable Static Route with IP SLA
Use IP SLA to monitor ISP connectivity and configure a static route as a backup.
ip sla 1 icmp-echo 8.8.8.8 source-interface GigabitEthernet0/1 timeout 1000 frequency 3 ip sla schedule 1 life forever start-time now track 1 ip sla 1 ip route 0.0.0.0 0.0.0.0 203.0.113.1 track 1 ip route 0.0.0.0 0.0.0.0 198.51.100.1 254
3. Policy-Based Routing
Implement PBR to route traffic based on specific policies.
access-list 101 permit ip 192.168.1.0 0.0.0.255 any route-map PBR-MAP permit 10 match ip address 101 set ip next-hop 203.0.113.1 interface GigabitEthernet0/1 ip policy route-map PBR-MAP
4. EEM to Clear NAT Translation Table
Use Embedded Event Manager (EEM) to clear the NAT translation table when ISPs go up or down.
event manager applet CLEAR-NAT event syslog pattern "Interface GigabitEthernet0/2, changed state to up" action 1 cli command "enable" action 2 cli command "clear ip nat translation *"
What Undercode Say
Policy-Based Routing with ISP failover is a robust solution for maintaining network uptime and optimizing traffic flow. By leveraging NAT, IP SLA, PBR, and EEM, network administrators can ensure seamless connectivity even during ISP outages. Below are additional commands and resources to enhance your understanding and implementation:
- Linux Command for Network Monitoring:
Use `ping` and `traceroute` to monitor network paths and latency.ping 8.8.8.8 traceroute 8.8.8.8
Windows Command for Network Diagnostics:
Use `tracert` and `pathping` for troubleshooting.
tracert 8.8.8.8 pathping 8.8.8.8
- Advanced Linux Networking:
Use `ip route` to manage routing tables.
ip route add default via 192.168.1.1 ip route show
For further reading, refer to Cisco’s official documentation on Policy-Based Routing and IP SLA.
By mastering these techniques, you can build resilient networks capable of handling real-world challenges effectively.
References:
Hackers Feeds, Undercode AI
