Looking for best solution to migration new Internet link with BGP defa

[kay.kang]

Hi, 

We're planning to replace the existing Internet link with new Internet link.

Currently, default route is advertised from the existing ISP via EBGP.

And, we will run EBGP peering with new ISP and they will advertise default route as well.

I was just thinking of using higher BGP weight value with the new Internet link and  keep the current default route as secondary for cutover Internet access(Outbound traffic) as potential migration solution.

For seamless and minimizing impact to Internet access, Is there any else recommendable way to migrate the new Internet link? 

[M02@rt37]

Hello @kay.kang,

Besides BGP weight, you might also consider using other BGP attributes such as AS Path length, local preference, or MED to influence the route selection. This can provide more granular control over traffic routing. Inbound and Outbound not only inbound on your Firewall and have an assymetric flow....

A higher Local-preference 'LP' could influence trafic towards the new ISP :: oubound. 

AS-Path could influence trafic from the new ISP :: inbound.

https://www.ciscopress.com/articles/article.asp?p=1565538&seqNum=4

[kay.kang]

We've got a public subnet to be advertised to the new ISP and we've got a routing design(using community and LP value) for inbound traffic from the ISP side to our side. Here, I am focusing on only outbound routing solution(regarding default route). Main goal is seamless migrating to the new ISP default route with minimizing or no impact to services using the existing default route.

[Giuseppe Larosa]

Hello @kay.kang ,

do you have your own provider indipendent public address block or up to now you are using a public address block that belongs to ISP1 the existing one ?

If you don't have your own PI public address block you need an appropriate NAT configuration on the firewall box to use the correct source IP addresses wen sending traffic to ISP1 and to ISP2 ( each of them in this scenario provides you a provider dependent public address block)

Hope to help

Giuseppe

[kay.kang]

We've got a public subnet to be advertised to the new ISP and we've got a routing design(using community and LP value) for inbound traffic from the ISP side to our side. Here, I am focusing on only outbound routing solution(regarding default route). Main goal is seamless migrating to the new ISP default route with minimizing or no impact to services using the existing default route.

[MHM Cisco World]

I send you message check it.