The answer to this problem will depend on the type of website traffic distinctions you desire for making, at the same time the edition of IOS you will be managing with your routers. CCIE Voice Training
There needs to be one thing that defines the various types of website traffic that you desire to prioritize. Usually, the more simple the distinctions are to build, the higher. It's because each of the exams get router resources and introduce processing delays. The most common policies for distinguishing among page views kinds make use of the packet's input interface and effortless IP header specifics this kind of as TCP port numbers. The subsequent examples indicate find out how to set an IP Precedence price of instant (2) for all FTP control site visitors that arrives by way of the serial0/0 interface, and an IP Precedence of concern (one) for all FTP knowledge targeted traffic. This distinction is feasible seeing that FTP manage targeted visitors uses TCP port 21, and FTP info works by using port 20.
The new method for configuring this employs course maps. Cisco initial launched this characteristic in IOS Version twelve.0(five)T. This process 1st defines a class-map that specifies how the router will determine this type of site traffic. It then defines a policy-map that truly 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 previously IOS versions, where class-maps happen to be not to choose from, you might have to employ policy-based routing to change the TOS field in a packet. Applying this coverage towards the interface tells the router make use of this coverage to test all incoming packets on this interface and rewrite the ones 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#
Right before you'll be able to tag a packet for exclusive remedy, you have got to acquire an especially clear concept of what varieties of site visitors demand exclusive remedy, along with precisely what kind of specific cure they may need to have. With the example, we now have chose to give a exclusive concern to FTP site visitors obtained on a exact serial interface. We exhibit techniques to do that making use of the two the outdated and new configuration approaches.
This may look to be a relatively synthetic illustration. Immediately after all, why would you treatment about tagging inbound potential customers that you simply have definitely obtained from a low-speed interface? Basically, amongst the most significant principles for employing QoS within a network is always that i suggest you consistently tag the packet as early as possible, preferably in the edges for the network. Then, as it passes with the network, just about every router only must investigate the tag, and does not will want to do any more classification. In cases like this, we'd make certain which the FTP potential customers returning within the other path is tagged from the first router that receives it. So the outbound traffic has previously been tagged, and it's a waste of router sources to reclassify the outbound packets.
Many organizations in fact just take this idea of marking on the edges one particular action even further, and remark any obtained packet. This may help to make certain that people are not requesting specific QoS privileges they are not allowed to acquire. Nonetheless, you ought to be mindful of this as a result of it might at times disrupt authentic markings. For example, a real-time software can use RSVP to reserve bandwidth through the network. Its imperative which the packets for this application hold the proper Expedited Forwarding (EF) DSCP marking or perhaps the network may not tackle them the right way. Although, additionally you don't prefer to allow other non-real-time programs from this exact supply hold the exact same EF concern level. So, in case you are heading to configure your routers to remark all incoming packets for the edges, ensure you have an understanding of what incoming markings are legitimate.
In that situation, the routers are managing DLSw to bridge SNA targeted visitors by an IP network. Therefore the routers by themselves in actual fact create the IP packets. This produces an additional problem considering the fact that there may be no incoming interface. To ensure recipe makes use of nearby policy-based routing. The fact which the router produces the packets also presents it a significant gain seeing that it does not have to consider any DLSw packets that might just come about to pass through.
The advantages within the newer class-map methodology aren't clear within this case in point, but one of several earliest giant rewards appears in order for you to work with the greater present day DSCP tagging scheme. Since the mature policy-based routing way will not instantly assist DSCP, you could have to faux it by environment equally the IP Precedence along with 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 invaluable later on during this chapter after we mention class-based weighted reasonable queuing and class-based targeted traffic shaping.
It will be important to note that in the course of this whole instance, we've only place a specific worth into your packet's TOS or DSCP industry. This, by alone, doesn't impact how the packet is forwarded by using the network. To perform that, it's essential to guarantee that as every single router inside network forwards these marked packets, the interface queues will react appropriately to this important information.
Eventually, we must always be aware that as this recipe shows two practical means of marking packets, using Committed Accessibility Charge (Car or truck) attributes. Automotive tends for being far more reliable on greater velocity interfaces.