The answer to this predicament depends upon the type of traffic distinctions you're looking for in making, likewise the edition of IOS you might be managing in your own routers. CCIE Voice Training

There need to be some thing that defines the different types of customers that you simply need to prioritize. On the whole, the more simple the distinctions are in making, the higher. This is because all the exams just take router sources and introduce processing delays. The most typical rules for distinguishing in between traffic kinds use the packet's input interface and straight forward IP header facts this sort of as TCP port quantities. The subsequent examples indicate methods to set an IP Precedence value of rapid (two) for all FTP control targeted visitors that arrives via the serial0/0 interface, and an IP Precedence of priority (1) for all FTP data potential customers. This distinction is possible considering the fact that FTP regulate potential customers uses TCP port 21, and FTP info takes advantage of port twenty.

The new way for configuring this employs class maps. Cisco initial launched this element in IOS Version 12.0(five)T. This process 1st defines a class-map that specifies how the router will identify this type of page views. It then defines a policy-map that really helps make the changes on the packet's TOS subject:

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 previously IOS versions, in which class-maps were not for sale, you have got to implement policy-based routing to alter the TOS area in a packet. Making use of this policy on the interface tells the router to utilize this policy 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#

Earlier than you can actually tag a packet for distinctive cure, you might have to obtain an especially clear strategy of what sorts of site visitors need to have exceptional treatment, together with exactly what kind of wonderful treatment they will might need. In the example, we've chose to give a unique priority to FTP visitors obtained on the specific serial interface. We exhibit a way to try this utilising equally the outdated and new configuration ways.
This may look to be a rather synthetic instance. Once all, why would you care about tagging inbound targeted visitors you have presently acquired from a low-speed interface? In actual fact, one of the most significant rules for utilizing QoS within a network is usually that make sure you constantly tag the packet as early as is possible, ideally for the edges of your network. Then, since it passes with the network, each and every router only must study the tag, and does not have to do any further classification. In this case, we might be sure that the FTP traffic returning with the other direction is tagged by the foremost router that gets it. And so the outbound site traffic has already been tagged, and it's a waste of router resources to reclassify the outbound packets.

A great many organizations ultimately just take this concept of marking for the edges a person stage further, and remark each acquired packet. This facilitates to make sure that end users aren't requesting specific QoS privileges they aren't permitted to have. Nonetheless, you need to be cautious of this for the reason that it can oftentimes disrupt legitimate markings. For instance, a real-time application may possibly use RSVP to reserve bandwidth with the network. It is actually imperative which the packets for this software have the proper Expedited Forwarding (EF) DSCP marking or perhaps the network may not take care of them properly. However, you also will not wish to let other non-real-time programs from this same exact resource possess the same EF priority degree. So, for anyone who is going to configure your routers to remark all incoming packets in the edges, make certain you comprehend what incoming markings are reputable.

In that situation, the routers are operating DLSw to bridge SNA potential customers by means of an IP network. And so the routers their selves truly construct the IP packets. This makes an extra problem considering there exists no incoming interface. To make sure that recipe takes advantage of local policy-based routing. The very fact that the router makes the packets also offers it an important edge merely because it doesn't have to take into account any DLSw packets which may just happen to go through.

The benefits for the newer class-map procedure are not noticeable on this illustration, but one of the many first of all significant merits seems if you would like to make use of the more modern DSCP tagging scheme. Since the older policy-based routing technique isn't going to directly support DSCP, you have got to pretend it by setting both equally the IP Precedence as well as the TOS individually 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 will even be beneficial afterwards on this chapter after we talk about class-based weighted truthful queuing and class-based website traffic shaping.
It is very important to notice that all over this complete illustration, now we have only put a wonderful value in to the packet's TOS or DSCP subject. This, by alone, won't have an affect on how the packet is forwarded because of the network. To accomplish that, it's essential to make sure that as each and every router within the network forwards these marked packets, the interface queues will react appropriately to this details.

Finally, we should observe that when this recipe displays two invaluable techniques of marking packets, utilising Committed Access Price (Auto) benefits. Car or truck tends to get increased reliable on higher velocity interfaces.

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