BGP Multihoming ISP level redundancy

Question:

 I want to go WS-C3750V2-24PS-S for ISP level redundancy,  with Dual internal Internet routers.  Public IP range is of /23. I want  BGP announcement of my discrete address block (e.g. /24) to their peers, in addition to the entire aggregated prefix (e.g. /23).

However I have only 2800 series routers with RAM of 768 MB (512+256).

Can you please suggest how should I proceed?

Answer:

You need to use a route-map applied outbound to eBGP neighbor to perform AS path prepending in a selective way
The route-map is ISP specific

border router 1:

ip prefix-list SECOND-ROUTE 4.4.5.0/24

route-map toISP1 permit 10
match ip address prefix  SECOND-ROUTE
set as-path prepend 100 100 100

route-map toISP1 permit 20
match ip address prefix IP_OUT

router bgp 100
no neigh 1.1.1.1 prefix-list IP_OUT out
neigh 1.1.1.1 route-map toISP2 out

In the same way for border router 2:

ip prefix-list FIRST-ROUTE 4.4.4.0/24

route-map toISP2 permit 10
match ip address prefix FIRST-ROUTE
set as-path prepend 100 100 100

route-map toISP2 permit 20
match ip address prefix IP_OUT

router bgp 100 WS-C3750V2-48PS-S Price
no neigh 2.2.2.2 prefix-list IP_OUT out
neigh 2.2.2.2 route-map toISP2 out

For more info, please refer to http://www.pereza.info/es/blog/traffic-shaping-and-layer-2-overhead