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Chapter 10
Route Optimization
Policy Routing Subnets
As another example, consider the following scenario. Company A has the
same ISP connections as in the previous example. Inside Company A, we
have two VLANs, the Engineering VLAN (172.16.3.0/24) and the Account-
ing VLAN (172.16.4.0/24), as illustrated in Figure 10.14. Our goal is to
direct traffic from the Engineering VLAN (172.16.3.0/24) out the 1.544Mbps
link (interface s0) and to direct traffic from the Accounting VLAN
(172.16.4.0/24) out the 56Kbps link (interface s1).
F I G U R E 1 0 . 1 4
Policy routing example 2
First, we need to create our access lists, specifying the conditions we're
looking for, that is, whether a packet was sourced from the Engineering or
Accounting VLAN:
access-list 1 permit 172.16.3.0 0.0.0.255
access-list 2 permit 172.16.4.0 0.0.0.255
Next, we need to create our route map and specify the match and set
parameters. In this example, we will use the name "routevlan":
route-map routevlan permit 10
match ip address 1
set interface serial0
!
Internet
172.16.2.2/24
172.16.1.2/24
56Kbps link
1.544Mbps link
172.16.1.1/24
172.16.2.1/24
172.16.3.1/24
172.16.4.1/24
s1
s0
e1
e0
ISP A
RouterB
ISP B
RouterC
RouterA
Company A
Engineering VLAN
Accounting VLAN
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