[c-nsp] Help with unique BGP setup

[Roman A. Nozdrin]

Lobo wrote:
> We're trying to do a custom bgp setup for one of our customers but I'm 
> not sure if it's even possible with IOS.  Our network has its primary 
> upstream connection in a different city from where this customer will 
> connect.  However each city has its own local internet connection as 
> well for backup purposes.  The market that this bgp customer is to be 
> turned up on uses the local isp connection as its primary due to 
> capacity issues on the intercity going back to the core city.
> 
> This customer's requirements for bandwidth can be met if they use the 
> local connection only but should the connection go down, they would most 
> likely saturate the intercity connection and impact everyone else.  What 
> has been proposed is that they will use the local connection to get 
> internet access and should this access go down, they want the bgp 
> session to be dropped or something equivalent that will make sure they 
> don't go over the intercity.
> 
> To my knowledge I know of no configuration that can drop a bgp session 
> based on some next hop attribute.  Is there some way to control this 
> customer's traffic as stated above?  Any examples you guys can offer?

I advise You to look at BGP conditional advertisement feature, which can 
be used on customers BGP peers. Hereby is an example.

neighbor city-link-nei-ip advertise-map cust-map non-exist-map checked-map

ip prefix-list cust-pref permit seq 5 permit cust-prefix/xx
ip prefix-list checked-pref permit seq 5 permit anyTIER1-pref/xx

route-map advertise-map permit 10
match ip address prefix-list cust-pref

route-map checked-map permit 10
match ip address prefix-list checked-pref

WBR
Roman A. Nozdrin