ISP-A = Lumen
ISP-B (OLD) = Spectrum
ISP-B (NEW) = AT&T
***We don’t have that many options for Tier 1 ISPs. ***
This is a typical migration. You have two ISPs and want to bring in a different one for many reasons. I’m going to go over a high-level migration plan. This is not a hard migration. It’s actually pretty easy and straightforward. Both circuits are running BGP, we are advertising our /24 subnet, and we receive partial routes from the ISP. I’m hoping this is a good start.
Here is a detailed migration plan with the necessary Cisco commands to replace the Spectrum circuit with AT&T, including BGP configuration:
1. Preparation Phase
Backup Configuration:
copy running-config startup-config
2. Installation Phase
Physical Connection:
Ensure the AT&T circuit is physically connected to the appropriate interface on the Inet-B Router (e.g., `GigabitEthernet0/1`).
3. Configuration Phase
BGP Configuration on Inet-B Router:
Add New BGP Neighbor (AT&T):*
conf t router bgp [Your_ASN] neighbor [ATT_IP_Address] remote-as [ATT_ASN] address-family ipv4 neighbor [ATT_IP_Address] activate neighbor [ATT_IP_Address] route-map [RM_INTET_IN] in neighbor [ATT_IP_Address] route-map [RM_INTET_OUT] out exit-address-family exit
Route Map Configuration for Partial Routes:
These can vary so much. Just make sure you have it configured just like the circuit you’re replacing.
4. Testing Phase
1. Initial Configuration and Verification:
Verify BGP Session:
show ip bgp summary
Verify Routes Received:
show ip bgp neighbors [ATT_IP_Address] received-routes
2. Test Failover with Spectrum Disabled:
Disable Spectrum BGP Session:
conf t router bgp [Your_ASN] neighbor [Spectrum_IP_Address] shutdown exit
Verify Failover to ATT:
– Temporarily disable the BGP session with Lumen to force traffic through ATT.
conf t router bgp [Your_ASN] neighbor [Lumen_IP_Address] shutdown exit
Monitor Traffic and Performance:
– Check routing and traffic to ensure it is going through AT&T.
show ip route show ip bgp
Re-enable Lumen BGP Session:
conf t router bgp [Your_ASN] no neighbor [Lumen_IP_Address] shutdown exit
Re-enable Spectrum BGP Session:
conf t router bgp [Your_ASN] no neighbor [Spectrum_IP_Address] shutdown exit
5. Permanent Decommissioning of Spectrum
Disable Spectrum BGP Session Permanently:
conf t router bgp [Your_ASN] neighbor [Spectrum_IP_Address] shutdown exit
Physical Disconnection:
Schedule and perform the physical disconnection of the Spectrum circuit.
Remove Spectrum BGP Configuration (Optional):
If you decide to remove the configuration entirely:
conf t router bgp [Your_ASN] no neighbor [Spectrum_IP_Address] exit
Final Verification
Final Check and Cleanup:
show ip bgp summary show ip route show running-config
Update Documentation:
Ensure all network documentation is updated to reflect the new setup.
This comprehensive plan and corresponding Cisco commands will guide you through replacing the Spectrum circuit with ATT, ensuring a smooth transition with minimal disruption.