A detailed workaround for the problem that Cisco IOS cannot do policy
based routing on 'match ip next-hop'.

This would be relatively trivial if it could, and RTR002 would be not
required at all.

I am no longer aware of any ISP using the below technique, however
it was used by at least one in the late 1990's when domestic traffic
was extremely badly priced due to monopolistic practices of the
incumbent telco in Australia.

The problem, in full:

  ISP A has links to Domestic Upstream B and International Upstream C.

  The link to B is congested outbound due to content but has excessive inbound.

  The link to C has surplus inbound and outbound, but higher latency.  The
  outbound to C is far less congested as most outbound content is
  domestic-bound but most inbound content is international-sourced.

  A wants to re-route latency insensitive traffic such as SMTP which would
  normally go directly to B to go via C instead, to provide a clean outbound
  path to B for latency-sensitive traffic.

================================================================================

RTR001

Purpose: ATM connection to provider including internal WAN trunks and
         upstream domestic connectivity on the same ATM.

Re-routing role:
         int f0/0.1 sends all latency-insensitive traffic received on any
         other interface to rtr002 for potential re-routing.  traffic
         received back on int f0/0.1 is assumed local and not subject to
         re-routing.

int f0/0
  desc Backbone LAN
  ip addr 192.168.0.1 255.255.255.0
  ip policy route-map domestic-remap
!
int f0/0.1
  desc Send/receive latency-insensitive traffic from/to rtr002/3 for rerouting
  ip addr 10.0.0.1 255.255.255.248
  encap dot1q 10
!
int a1/0.1
  desc Interstate WAN PVC
  ip addr 192.168.1.1 255.255.255.252
  ip policy route-map domestic-remap
!
int a1/0.2
  desc PVC to domestic upstream with outbound congestion
  ip addr 192.168.2.1 255.255.255.252
!
route-map domestic-remap permit 10
  match ip address 123
  set ip next-hop 10.0.0.2
!
route-map domestic-remap permit 20
!
route-map no-domestic permit 10
  match community 10
!
route-map no-domestic deny 20
!
route-map tag-domestic permit 10
  set community 65535:1000
!
ip bgp community new-format
!
ip community-list 10 deny 65535:1000
ip community-list 10 permit internet
!
access-list 123 permit ip any any eq 25
access-list 123 permit ip any eq 25 any
!
router bgp 65535
  neighbour 10.0.0.2 remote-as 65535
  neighbour 10.0.0.2 route-reflector-client
  neighbour 10.0.0.2 send-community
  neighbour 10.0.0.2 route-map no-domestic out
  neighbour 192.168.0.3 remote-as 65535
  neighbour 192.168.0.3 route-reflector-client
  neighbour 192.168.0.3 send-community
  neighbour 192.168.1.2 remote-as 65535
  neighbour 192.168.1.2 route-reflector-client
  neighbour 192.168.1.2 send-community
  neighbour 192.168.2.2 remote-as 65534
  neighbour 192.168.2.2 route-map tag-domestic in

RTR002

Purpose: To re-route latency-insensitive traffic via second upstream with
         more outgoing bandwidth but higher latency.  Exists only on
         VLAN 10 (by switch config).

Re-routing role:
         int f0/0 receives latency insensitive traffic.  traffic destined
         for internal or peer addresses is returned to rtr001, traffic which
         is destined to something not in the routing table is sent to rtr003
         to be sent out the latency insensitive link.

int f0/0
  desc Send/receive latency-insensitive traffic from/to rtr001/3 for rerouting
  ip addr 10.0.0.2 255.255.255.248
!
ip route 0.0.0.0 0.0.0.0 10.0.0.3
!
router bgp 65535
  neighbour 10.0.0.1 remote-as 65535
  neighbour 10.0.0.1 route-reflector-client
  neighbour 10.0.0.1 send-community
  neighbour 10.0.0.1 route-map munge-nexthop in
!
route-map munge-nexthop permit 10
  set ip next-hop 10.0.0.1


RTR003

Purpose: DS3 link to international upstream provider.

Re-routing role:
         int f1/0.1 receives latency insentive domestic or international
         traffic.  this traffic is sent directly out the international
         upstream.

int f0/0
  desc Backbone LAN
  ip addr 192.168.0.3 255.255.255.0
!
int f0/0.1
  desc Receive latency insensitive traffic from rtr001 via rtr002 for rerouting
  ip addr 10.0.0.3 255.255.255.248
  encap dot1q 10
  ip policy route-map domestic-remap
!
int s1/0
  desc DS3 to international upstream
  ip addr 192.168.3.1 255.255.255.252
!
ip route 0.0.0.0 0.0.0.0 192.168.3.2
!
route-map domestic-remap permit 10
  set ip next-hop 192.168.3.2
!
router bgp 65535
  neighbour 192.168.0.1 remote-as 65535
  neighbour 192.168.0.1 route-reflector-client
  neighbour 192.168.0.1 send-community
  neighbour 192.168.3.2 remote-as 65533