QoS marking on cisco IOS Router

1. QOS MARKING ON CISCO IOS ROUTER
Quality of Service (QoS) | www.netprotocolxpert.in

2. • Marking means that we set the TOS (Type of Service) byte with an IP
Precedence value or DSCP value.
• Marking on a Cisco catalyst switch is a bit different than on a router.

3. CONFIGURATION
• We will send some traffic from R1 to R3 and we will use R2 to mark our traffic. We’ll
keep it simple and start by marking telnet traffic.

4. • Let’s create an access-list for classification:
• R2(config)#ip access‐list extended TELNET‐TRAFFIC
• R2(config‐ext‐nacl)#permit tcp any any eq telnet
• Now we need to add the access-list to a class-map:
• R2(config)#class‐map TELNET‐TRAFFIC
• R2(config‐cmap)#match access‐group name TELNET‐TRAFFIC

5. AND WE’LL ADD THE CLASS-
MAP TO A POLICY-MAP:
• R2(config)#policy‐map MARKING
• R2(config‐pmap)#class TELNET‐TRAFFIC
• R2(config‐pmap‐c)#set ?
• atm‐clp Set ATM CLP bit to 1
• cos Set IEEE 802.1Q/ISL class of service/user priority
• cos‐inner Set Inner CoS
• discard‐class Discard behavior identifier
• dscp Set DSCP in IP(v4) and IPv6 packets
• fr‐de Set FR DE bit to 1
• ip Set IP specific values
• mpls Set MPLS specific values
• precedence Set precedence in IP(v4) and IPv6 packets
• qos‐group Set QoS Group
• vlan‐inner Set Inner Vlan

6. • There are quite some options for the set command. When it comes to IP packets
we’ll use the precedence or DSCP values. Let’s start with precedence:
• R2(config‐pmap‐c)#set precedence ?
• <0‐7> Precedence value
• cos Set packet precedence from L2 COS
• critical Set packets with critical precedence (5)
• flash Set packets with flash precedence (3)
• flash‐override Set packets with flash override precedence (4)
• immediate Set packets with immediate precedence (2)
Cont.…

7. • internet Set packets with internetwork control precedence (6)
• network Set packets with network control precedence (7)
• priority Set packets with priority precedence (1)
• qos‐group Set packet precedence from QoS Group.
• routine Set packets with routine precedence (0)

8. • Let’s go for IP precedence 7 (network):
• R2(config‐pmap‐c)#set precedence network
• Last but not least, we have to activate the policy-map:
• R2(config)#interface FastEthernet 0/0
• R2(config‐if)#service‐policy input MARKING
• Telnet from R1 to R3:
• R1#telnet 192.168.23.3
• Trying 192.168.23.3 ... Open

9. • R2#show policy‐map interface FastEthernet 0/0
• FastEthernet0/0
• Service‐policy input: MARKING
• Class‐map: TELNET‐TRAFFIC (match‐all)
• 10 packets, 609 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: access‐group name TELNET‐TRAFFIC
• QoS Set
• precedence 7
• Packets marked 10
Cont.…

10. • Class‐map: class‐default (match‐any)
• 0 packets, 0 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: any
• 10 packets have been marked with precedence 7.

11. • Also mark some packets with a DSCP value, let’s mark some HTTP traffic:
• R2(config)#ip access‐list extended HTTP‐TRAFFIC
• R2(config‐ext‐nacl)#permit tcp any any eq 80
• Create a class-map:
• R2(config)#class‐map HTTP‐TRAFFIC
• R2(config‐cmap)#match access‐group name HTTP‐TRAFFIC

12. ADD TO THE POLICY-MAP:
• R2(config)#policy‐map MARKING
• R2(config‐pmap)#class HTTP‐TRAFFIC
• R2(config‐pmap‐c)#set dscp ?
• <0‐63> Differentiated services codepoint value
• af11 Match packets with AF11 dscp (001010)
• af12 Match packets with AF12 dscp (001100)
• af13 Match packets with AF13 dscp (001110)
• af21 Match packets with AF21 dscp (010010)
• af22 Match packets with AF22 dscp (010100)
• af23 Match packets with AF23 dscp (010110)
• af31 Match packets with AF31 dscp (011010)
• af32 Match packets with AF32 dscp (011100)
• af33 Match packets with AF33 dscp (011110)
Cont.…

13. • af41 Match packets with AF41 dscp (100010)
• af42 Match packets with AF42 dscp (100100)
• af43 Match packets with AF43 dscp (100110)
• cos Set packet DSCP from L2 COS
• cs1 Match packets with CS1(precedence 1) dscp (001000)
• cs2 Match packets with CS2(precedence 2) dscp (010000)
• cs3 Match packets with CS3(precedence 3) dscp (011000)
• cs4 Match packets with CS4(precedence 4) dscp (100000)
• cs5 Match packets with CS5(precedence 5) dscp (101000)
• cs6 Match packets with CS6(precedence 6) dscp (110000)
• cs7 Match packets with CS7(precedence 7) dscp (111000)
• default Match packets with default dscp (000000)
• ef Match packets with EF dscp (101110)
• qos‐group Set packet dscp from QoS Group.

14. • Let’s pick AF12
• R2(config‐pmap‐c)#set dscp af12
• Let’s generate some traffic:
• R3(config)#ip http server
• R1#telnet 192.168.23.3 80
• Trying 192.168.23.3, 80 ... Open

15. CHECK OUT THE POLICY-MAP:
• R2#show policy‐map interface FastEthernet 0/0
• FastEthernet0/0
• Service‐policy input: MARKING
• Class‐map: TELNET‐TRAFFIC (match‐all)
• 10 packets, 609 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: access‐group name TELNET‐TRAFFIC
• QoS Set
• precedence 7
• Packets marked 10
Cont.…

16. • Class‐map: HTTP‐TRAFFIC (match‐all)
• 3 packets, 180 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: access‐group name HTTP‐TRAFFIC
• QoS Set
• dscp af12
• Packets marked 3
• Class‐map: class‐default (match‐any)
• 99 packets, 5940 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: any

17. • Some network devices like switches or wireless controllers sometimes re-mark
traffic, this can be a pain and it's something you might want to check.
• On a Cisco IOS router it's simple to do this. just create a policy-map and some
classmaps that match on your precedence or DSCP values. This allows you to quickly
check if you are receiving (correctly) marked packets or not.

18. • R3(config)#class‐map AF12
• R3(config‐cmap)#match dscp af12
• R3(config)#class‐map PREC7
• R3(config‐cmap)#match precedence 7
• R3(config)#policy‐map COUNTER
• R3(config‐pmap)#class AF12
• R3(config‐pmap‐c)#exit
• R3(config‐pmap)#class PREC7
• R3(config‐pmap‐c)#exit
• R3(config)#interface FastEthernet 0/0
• R3(config‐if)#service‐policy input COUNTER
I created two class-maps
that match on DSCP AF12
or precedence 7 marked
packets.

19. • R3#show policy‐map interface FastEthernet 0/0
• FastEthernet0/0
• Service‐policy input: COUNTER
• Class‐map: AF12 (match‐all)
• 4 packets, 240 bytes
• 5 minute offered rate 0 bps
• Match: dscp af12 (12)
• Class‐map: PREC7 (match‐all)
• 12 packets, 729 bytes
• 5 minute offered rate 0 bps
• Match: precedence 7
• Class‐map: class‐default (match‐any)
• 0 packets, 0 bytes
• 5 minute offered rate 0 bps, drop rate 0 bps
• Match: any
This proves that R3 is
receiving our marked
packets.

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