Full BGP routes Multi homed

[alshamlan]

dears

ww have mutihomed ISPs where we are receiving the full bgp routes from all of ISPs 

case: we have a latency complain to certain destination and need to assur that the selected path ISP having the optimum latency. When we checked, the routed is default selected the shortest as path isp, now we need to check the latency results of all ISPs,

what is the best practice to route traffic sourced from certain subnet to go to certain destination, swaping from ISP to other and compare the results, the challenge that outbound traffic will remains consider the shortest as path in the full bgp routes

i hope I could explain the required 

thanks 

YouSif 

[Julio E. Moisa]

Hi

Please correct If im understanding wrong, but if you want to manipulate certain traffic to swap the path to other ISP and reach a specific destination, you could use highest local preference.

Example

ip prefix-list DESTINATION seq 5 permit 100.0.0.1/32

route-map TEST permit 5
match ip address prefix DESTINATION
set local-preference 10000

route-map TEST permit 100

router bgp 100
neighbor 2.2.2.2 route-map TEST in

Hope it is useful

:-)

[alshamlan]

Thanks 

this is a way where it will change the outbound for the destination, hence if the route is very bad the live traffic will be affected during the testing, I am looking for a best practice technique to do testing without affecting the live traffic to destinations.  

[Spooster IT Services]

Hi alshamlan,

Policy based routing is the best practice to test the path on the basis of source of destination.

ip access-list extended PBR
permit ip SOURCE_SUBNET DESTINATION_SUBNET

route-map PBR permit 10
match ip address PBR
set ip next-hop <NEXT HOP IP/ISP end router's IP>

Interface Gigx/x <recieving Interface>

ip policy route-map PBR

It will only effect the traffic coming from source that you will define in ACL not live traffic.

[cofee]

Julio and Spooster suggestions will give you the same result. Julio's recommendation will only set the local preference higher for the destination host without affecting anything else.

[Spooster IT Services]

Hi alshamlan,

Setting local preference higher will effect all the traffic for the destination for whom you will change the local preference where as by using policy based routing you can effect the traffic based on source and destination.

@cofee@0400 both suggestions will not give the same result. 

[cofee]

You are correct. I was just looking at it from destination prefix/host perspective.

[Joseph W. Doherty]

PfR can dynamically change outbound paths based on current latency (also and/or drops and/or throughput).

It's been some time since I've used it, and I had used its "original" variant, OER, but I found I could eliminate the taking of full BGP Internet tables from my ISPs and just take a default and let OER find the optimal egress path.

[alshamlan]

Can you please give an example of this PfR dynamic cahnges 

[Joseph W. Doherty]

What would you consider an example?

[a.alekseev]

it's not possible. BGP itself cannot analyse latency.