использовать vrf или pbr
для VRF будет примерно так
ip vrf vrf1
int vlan 100
ip vrf forwarding vrf1
ip address 10.0.0.1 255.255.255.0
int vlan 200
ip vrf forwarding vrf1
ip address 172.16.0.6 255.255.255.248
ip route vrf vrf1 0.0.0.0 0.0.0.0 172.16.0.2
для PBR
ip access-list extended acl-clients-10-0-0
permit ip 10.0.0.0 0.0.0.255 any
route-map gate2 permit 10
match ip acl-clients-10-0-0
set ip default next-hop 172.16.0.2
interface Vlan100
ip address 10.0.0.1 255.255.255.0
ip policy route-map gate2
