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QoS — the policy that will not attach
Enterprise Intermediate 6 devices 4 checked tasks 100 points Plan lab
A branch router with voice and data heading out of one WAN interface. The class-maps and policy-map are already written, and `service-policy output` refuses them. Read the error — it names the class, what it asked for, and what was actually left. You build it in a browser, type real commands at each device, and every task below is
checked against the running configuration — so you find out it is wrong before anybody else does.
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The scenario
A branch router with voice and data heading out of one WAN interface. The class-maps and policy-map are already written, and `service-policy output` refuses them. Read the error — it names the class, what it asked for, and what was actually left.
Your role: a network engineer on the enterprise team. Level: Intermediate Done when: all 4 goals show as passed (100 points).
Network status
Devices: 2 PCs, 1 switch, 2 routers, 1 server, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. Phone is a host with 10.10.10.20/24, gateway 10.10.10.1. PC1 is a host with 10.10.10.10/24, gateway 10.10.10.1. Branch starts with addresses (F0/0 10.10.10.1/24, S0/0/0 10.0.0.1/30) and OSPF 1 already configured. HQ starts with addresses (F0/0 10.20.20.1/24, S0/0/0 10.0.0.2/30) and OSPF 1 already configured. HQ-SRV is a host with 10.20.20.10/24, gateway 10.20.20.1. SW1 starts with an empty configuration. Known problems
The network worked and now does not: the scenario above says what users report. The cause is a configuration fault, not a cable. Find it with show commands (interfaces, routes, neighbours, running-config) before you change anything; fix only what is wrong. Goals
The policy is attached outbound on the WAN interface (40 pts) Voice is still served first — the priority class survived (20 pts) The reservation fits — nothing asks for more than is available (20 pts) The branch can still reach the HQ server (20 pts) The activity, in order
The policy is attached outbound on the WAN interface Why: Each goal is a state the lab can check on the running device. Verify with: show running-config Voice is still served first — the priority class survived Why: Each goal is a state the lab can check on the running device. Verify with: show running-config The reservation fits — nothing asks for more than is available Why: Each goal is a state the lab can check on the running device. Verify with: show running-config The branch can still reach the HQ server Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.20.20.10 Tips
Work in the order given: later goals depend on the earlier ones. After every change, run the verify command before moving on; do not guess. Stuck? Read the verify output first. It names the interface, neighbour or route that is wrong. Why this matters
A branch router with voice and data heading out of one WAN interface. The class-maps and policy-map are already written, and `service-policy output` refuses them. Read the error — it names the class, what it asked for, and what was actually left.
What you will be able to do
The policy is attached outbound on the WAN interface
Voice is still served first — the priority class survived
The reservation fits — nothing asks for more than is available
The branch can still reach the HQ server
The network
PC, Switch 8-port, ISR 1841, Server — 6 devices in all, already cabled.
Fa0 Fa0/1 Fa0 Fa0/2 Fa0/8 Fa0/0 10.10.10.1/24 Se0/0/0 10.0.0.1/30 Se0/0/0 10.0.0.2/30 Fa0/0 10.20.20.1/24 Fa0 Phone 10.10.10.20/24 · gw 10.10.10.1 PC1 10.10.10.10/24 · gw 10.10.10.1 SW1 Branch HQ HQ-SRV 10.20.20.10/24 · gw 10.20.20.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
Phone PC 10.10.10.20 / 255.255.255.0 gw 10.10.10.1 PC1 PC 10.10.10.10 / 255.255.255.0 gw 10.10.10.1 SW1 Switch 8-port configure it Branch ISR 1841 configure it HQ ISR 1841 configure it HQ-SRV Server 10.20.20.10 / 255.255.255.0 gw 10.20.20.1
Cabling
Phone Fa0 ↔ SW1 Fa0/1 PC1 Fa0 ↔ SW1 Fa0/2 SW1 Fa0/8 ↔ Branch Fa0/0 Branch Serial0/0/0 ↔ HQ Serial0/0/0 HQ Fa0/0 ↔ HQ-SRV Fa0
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
Branch interface f0/0
ip address 10.10.10.1 255.255.255.0
no shutdown
exit
interface s0/0/0
ip address 10.0.0.1 255.255.255.252
no shutdown
exit
router ospf 1
router-id 1.1.1.1
network 0.0.0.0 255.255.255.255 area 0
exit
class-map match-all VOICE
match dscp ef
exit
class-map match-any SIGNALLING
match dscp cs3 af31
exit
policy-map WAN-OUT
class VOICE
priority percent 40
exit
class SIGNALLING
bandwidth percent 40
exit
class class-default
fair-queue
exit
exit HQ interface f0/0
ip address 10.20.20.1 255.255.255.0
no shutdown
exit
interface s0/0/0
ip address 10.0.0.2 255.255.255.252
no shutdown
exit
router ospf 1
router-id 2.2.2.2
network 0.0.0.0 255.255.255.255 area 0 Tasks, and how each one is checked
Every task is decided by reading the live network — a neighbour in FULL, a ping that succeeds, a line in the running configuration — not by looking for a keyword you typed. The same command shows you what the lab sees.
# Task Pts How to verify it yourself
1 The policy is attached outbound on the WAN interface 40 Checked automatically against the device’s live state (policyOut). 2 Voice is still served first — the priority class survived 20 Checked automatically against the device’s live state (qosPriority). 3 The reservation fits — nothing asks for more than is available 20 Checked automatically against the device’s live state (policyFits). 4 The branch can still reach the HQ server 20 On PC1: ping 10.20.20.10 must succeed.
Stuck? Ask the coach
Tell the coach what you see or what you tried. It gives you a hint, not the answer, the way a senior engineer would. Included with a free trial or any plan.
Ask the coach
Reference solution
Try it yourself first — the lab checks your work either way. This is one configuration that makes every task pass, device by device:
Branch policy-map WAN-OUT
class VOICE
priority percent 33
exit
class SIGNALLING
bandwidth percent 5
exit
exit
interface s0/0/0
service-policy output WAN-OUT Where this is examined
This lab practises these topics in the zNetLaB certification courses:
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