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Network Engineer — 08. Policy-Based Routing (PBR)

2025-10-26 Networking PBR IP SLA Routing Cisco OTUS

Policy-Based Routing (PBR)

Assignment

Goal: Configure routing policy for the Chokurdakh office and distribute traffic between 2 uplinks.

In this lab you are expected to independently:

  1. Configure routing policy for the Chokurdakh office networks
  2. Distribute traffic between the two provider uplinks in Chokurdakh
  3. Configure link tracking via IP SLA in Chokurdakh
  4. Configure a default route for the Labytnangi office
  5. Document the plan and changes

Note: verify-availability in route-map may not work for IPv6.

PBR

DevicePortIPv4IPv6NoteRegion
R27e0/0210.110.35.2/302CAD:1995:B0DA:A::27R25(Triada)Labytnangi
R28e0/0111.110.35.14/302CAD:1995:B0DA:7::28R26(Triada)Chokurdakh
e0/1111.110.35.10/302CAD:1995:B0DA:8::28R25(Triada)
e0/2172.16.40.1/242CAD:1995:B0DA:9::28SW29(Chokurdah)
VPC30172.16.40.102cad:1995:b0da:9::10
VPC31172.16.40.112cad:1995:b0da:9::11

Configure routing policy for the Chokurdakh office networks

R28 — interface addresses

R28#show ipv6 int brief
Ethernet0/0            [up/up]
    FE80::A8BB:CCFF:FE01:C000
    2CAD:1995:B0DA:7::28
Ethernet0/1            [up/up]
    FE80::A8BB:CCFF:FE01:C010
    2CAD:1995:B0DA:8::28
Ethernet0/2            [up/up]
    FE80:21::28
    2CAD:1995:B0DA:9::28

R28#show ip int bri
Interface                  IP-Address      OK? Method Status                Protocol
Ethernet0/0                111.110.35.14   YES manual up                    up
Ethernet0/1                111.110.35.10   YES manual up                    up
Ethernet0/2                172.16.40.1     YES manual up                    up

ACL ACL1 matches traffic from VPC30 (172.16.40.10) and the route-map steers it via R26 (e0/0). A static route to R25’s loopback (215.215.215.215) is added to verify the alternate path — the provider side runs OSPF with no additional configuration required.

R28

enable
configure terminal

ip route 215.215.215.215 255.255.255.255 111.110.35.9


ip access-list extended ACL1
permit ip host 172.16.40.10 any


route-map TEST permit 10
match ip address ACL1
set ip next-hop 111.110.35.13
set ipv6 next-hop 2CAD:1995:B0DA:7::26


interface Ethernet0/2
ip policy route-map TEST
end
copy running-config startup-config

VPC30 trace before and after applying the route-map:

VPC30

enable
configure terminal
! Before route-map
VPCS> trace 215.215.215.215
trace to 215.215.215.215, 8 hops max, press Ctrl+C to stop
 1   172.16.40.1   0.551 ms  0.369 ms  0.357 ms
 2   *111.110.35.9   1.014 ms (ICMP type:3, code:3, Destination port unreachable)  *

! After route-map
VPCS> trace 215.215.215.215
trace to 215.215.215.215, 8 hops max, press Ctrl+C to stop
1   172.16.40.1   0.629 ms  0.560 ms  0.463 ms
2   111.110.35.13   0.902 ms  0.655 ms  0.590 ms
3   *10.10.30.9   0.882 ms (ICMP type:3, code:3, Destination port unreachable)  *
end
copy running-config startup-config

Two IP SLA probes monitor reachability to each provider next-hop. Tracked objects are referenced in both the default routes and the route-map:

R28

enable
configure terminal
ip sla 1
 icmp-echo 111.110.35.9 source-interface Ethernet0/1
 frequency 5
ip sla schedule 1 life forever start-time now
!
ip sla 2
 icmp-echo 111.110.35.13 source-interface Ethernet0/0
 frequency 5
ip sla schedule 2 life forever start-time now
!
track 1 ip sla 1 reachability
track 2 ip sla 2 reachability
!
ip route 0.0.0.0 0.0.0.0 111.110.35.9 track 1
ip route 0.0.0.0 0.0.0.0 111.110.35.13 track 2

! Updated route-map with availability verification
route-map TEST permit 10
match ip address ACL1
set ip next-hop verify-availability 111.110.35.9 10 track 1
set ip next-hop verify-availability 111.110.35.13 15 track 2
end
copy running-config startup-config

R28 — show track / show route-map

R28#show track 1
Track 1
  IP SLA 1 reachability
  Reachability is Up
    13 changes, last change 00:40:47
  Latest operation return code: OK
  Latest RTT (millisecs) 1
  Tracked by:
    ROUTE-MAP 0
    STATIC-IP-ROUTING 0

R28#show track 2
Track 2
IP SLA 2 reachability
Reachability is Up
7 changes, last change 01:09:14
Latest operation return code: OK
Latest RTT (millisecs) 1
Tracked by:
ROUTE-MAP 0
STATIC-IP-ROUTING 0


R28#show route-map
route-map TEST, permit, sequence 10
Match clauses:
ip address (access-lists): ACL1
Set clauses:
ip next-hop verify-availability 111.110.35.9 10 track 1  [up]
ip next-hop verify-availability 111.110.35.13 15 track 2  [up]
ipv6 next-hop 2CAD:1995:B0DA:7::26
Policy routing matches: 234 packets, 24284 bytes

Configure a default route for the Labytnangi office

R27

enable
configure terminal
R27(config)#do sh run | s route
ip route 0.0.0.0 0.0.0.0 210.110.35.1
ipv6 route ::/0 2CAD:1995:B0DA:A::25
end
copy running-config startup-config

Network Engineer Course | Lab 08

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