The solution to this drawback depends on the type of customers distinctions you want for making, in addition the version of IOS you will be running inside of your routers.
There must be a little something that defines the different forms of targeted visitors that you need to prioritize. Normally, the easier the distinctions are for making, the higher. It's because each of the tests consider router assets and introduce processing delays. The most common rules for distinguishing in between potential customers forms use the packet's input interface and simple and easy IP header knowledge this sort of as TCP port quantities. The following examples indicate tips on how to set an IP Precedence value of rapid (2) for all FTP control website traffic that arrives by way of the serial0/0 interface, and an IP Precedence of priority (1) for all FTP information page views. This distinction is feasible since FTP regulate site visitors takes advantage of TCP port 21, and FTP information uses port 20.
The newest technique for configuring this makes use of class maps. Cisco first of all launched this attribute in IOS Model twelve.0(5)T. This method to begin with defines a class-map that specifies how the router will recognize this kind of targeted visitors. It then defines a policy-map that actually makes the adjustments towards the packet's TOS field:
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#access-list 101 permit any eq ftp any
Router(config)#access-list 101 permit any any eq ftp
Router(config)#access-list 102 permit any eq ftp-data any
Router(config)#access-list 102 permit any any eq ftp-data
Router(config)#class-map match-all ser00-ftpcontrol
Router(config-cmap)#description branch ftp control traffic
Router(config-cmap)#match input-interface serial0/0
Router(config-cmap)#match access-group 101
Router(config-cmap)#exit
Router(config)#class-map match-all ser00-ftpdata
Router(config-cmap)#description branch ftp data traffic
Router(config-cmap)#match input-interface serial0/0
Router(config-cmap)#match access-group 102
Router(config-cmap)#exit
Router(config)#policy-map serialftppolicy
Router(config-pmap)#description branch ftp traffic policy
Router(config-pmap)#class ser00-ftpcontrol
Router(config-pmap-c)#set ip precedence immediate
Router(config-pmap-c)#exit
Router(config-pmap)#class ser00-ftpdata
Router(config-pmap-c)#set ip precedence priority
Router(config-pmap-c)#exit
Router(config-pmap)#exit
Router(config)#interface serial0/0
Router(config-if)#ip route-cache policy
Router(config-if)#service-policy input serialftppolicy
Router(config-if)#exit
Router(config)#end
Router#
For before IOS variations, the place class-maps have been not obtainable, you have to use policy-based routing to change the TOS field in the packet. Making use of this coverage to your interface tells the router to make use of this coverage to check all incoming packets on this interface and rewrite those that match the route map:Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#access-list 101 permit any eq ftp any
Router(config)#access-list 101 permit any any eq ftp
Router(config)#access-list 102 permit any eq ftp-data any
Router(config)#access-list 102 permit any any eq ftp-data
Router(config)#route-map serialftp-rtmap permit 10
Router(config-route-map)#match ip address 101
Router(config-route-map)#set ip precedence immediate
Router(config-route-map)#exit
Router(config)#route-map serialftp-rtmap permit 20
Router(config-route-map)#match ip address 102
Router(config-route-map)#set ip precedence priority
Router(config-route-map)#exit
Router(config)#interface serial0/0
Router(config-if)#ip policy route-map serialftp-rtmap
Router(config-if)#ip route-cache policy
Router(config-if)#exit
Router(config)#end
Router#
Well before you can tag a packet for extraordinary treatment, you could have to possess an incredibly apparent thought of what forms of targeted traffic absolutely need particular procedure, not to mention precisely what kind of particular treatment they'll would need. Inside instance, we have now chose to give a exceptional priority to FTP page views received on a targeted serial interface. We clearly show simple tips to try this utilizing equally the previous and new configuration ways.
This may seem to become a fairly synthetic case in point. After all, why would you treatment about tagging inbound visitors you have presently received from a low-speed interface? Genuinely, among the list of most vital concepts for employing QoS in a network is that be certain to usually tag the packet as early as feasible, preferably at the edges of this network. Then, as it passes through the network, every single router only must investigate the tag, and won't should do any extra classification. In this case, we would be sure which the FTP website traffic returning from the other gestion is tagged through the earliest router that gets it. So the outbound targeted visitors has by now been tagged, and it's a waste of router resources to reclassify the outbound packets.
A great number of organizations genuinely get this concept of marking on the edges a single stage additionally, and remark every last acquired packet. This allows to be sure that customers aren't requesting particular QoS privileges they aren't allowed to possess. However, you should be careful of this considering the fact that it may possibly every now and then disrupt legit markings. Such as, a real-time software might possibly use RSVP to order bandwidth through the network. It happens to be really important the packets for this software possess the appropriate Expedited Forwarding (EF) DSCP marking or the network won't tackle them correctly. Then again, additionally you do not aspire to allow other non-real-time applications from this identical source possess the identical EF priority degree. So, when you are heading to configure your routers to remark all incoming packets with the edges, be certain that you realize what incoming markings are respectable.
In that situation, the routers are managing DLSw to bridge SNA targeted visitors via an IP network. So the routers on their own really create the IP packets. This produces a further challenge since there is certainly no incoming interface. In order that recipe usages localized policy-based routing. The fact the router makes the packets also offers it a significant benefit simply because it does not have to consider any DLSw packets that may just come about to pass through.
The advantages on the newer class-map strategy are not noticeable during this example, but one of the many very first enormous positive aspects seems if you need make use of the greater contemporary DSCP tagging scheme. Because the older policy-based routing methodology will not immediately support DSCP, you've to faux it by environment equally the IP Precedence additionally, the TOS independently as follows.
Router(config)#route-map serialftp-rtmap permit 10
Router(config-route-map)#match ip address 115
Router(config-route-map)#set ip precedence immediate
Router(config-route-map)#set ip tos max-throughput
In this case, the packet will wind up with an IP Precedence value of immediate, or 2 (010 in binary), and TOS of max-throughput, or 4 (0100 in binary).
Doing the same thing with the class-map method is much more direct:
Router(config)#policy-map serialftppolicy
Router(config-pmap)#class serialftpclass
Router(config-pmap-c)#set ip dscp af21
Class-maps may even be helpful afterwards within this chapter once we speak about class-based weighted fair queuing and class-based targeted traffic shaping.
It's important to notice that during this entire case in point, we now have only place a particular value into your packet's TOS or DSCP area. This, by by itself, isn't going to have an impact on how the packet is forwarded by the network. To perform that, you must be certain that as every router within the network forwards these marked packets, the interface queues will react appropriately to this facts.
Last but not least, we should always note that whilst this recipe shows two useful approaches of marking packets, utilizing Committed Entry Fee (Vehicle) options. Auto tends to get a good deal more successful on larger speed interfaces.