Step 3 Design Individual QoS Mechanisms

This figure shows the third requirement, consisting of the following:

■ BGP routes that are received into AS 12 from AS 73 will be marked with a community value of 12:17 on the point of presence (POP) router.

■ Community propagation will have to be configured on the POP router so that the community value of 12:17, set on the POP router, will be propagated to the NAP router.

■ All the BGP routes with a community of 12:17 in the IP routing table and the FIB table on the AS 12 NAP routers will contain the IP precedence flash.

Mark Routes Coming from AS 73

The figure shows the configuration that is necessary to meet the requirement that routes coming from AS 73 will be marked with the special community value of 12:17.

Use this configuration on the POP router to mark BGP routes from AS 73 with the community value 12:17:

router bgp 12 neighbor 1.2.3.4 remote-as 73 neighbor 1.2.3.4 route-map Premium in

route-map Premium permit 10 set community 12:17 additive

Configure Community Propagation s o1

router bgp 12

neighbor 2.3.4

5 remote-as 12

neighbor 2.3.4

5 send-community

s o1

The figure shows the configuration that is necessary to propagate the special community value, 12:17, which has been added on the POP router and will be seen on the NAP router.

The following configuration is used on the POP router to mark to propagate the community value (12:17) to the NAP router:

router bgp 12 neighbor 2.3.4.5 remote-as 12 neighbor 2.3.4.5 send-community

Set FIB Table Based on BGP Community

The NAP router in AS 12 uses a route map to translate BGP community values into appropriate IP precedence values. This figure illustrates how all BGP routes carrying BGP community 12:17 are tagged with IP precedence flash in the routing table and the FIB table. All other BGP routes are tagged with IP precedence 0.

The following configuration is used on the NAP router to set or change the IP precedence of those BGP routes that match the community value (12:17):

router bgp 12 table-map PremiumCheck

route-map PremiumCheck permit 10 match community 17 set ip precedence flash

route-map PremiumCheck permit 20 set ip precedence 0

ip community-list 17 permit 12:17

The configuration shows that if the route map PremiumCheck matches the community attribute of 12:17, the corresponding packet will have its IP precedence changed to flash, as required in the example.

Configure CEF Packet Marking

The last configuration step is to enable CEF-based marking on the NAP router in AS 12. This example requires that all packets going to (destination-based marking) the customer network (AS 73) be marked with IP precedence flash.

In this case, the AS 12 NAP router HSSI 0/0 interface connects to AS 24. Therefore, the bgp-policy destination ip-prec-map command is configured under the HSSI 0/0 interface to enable destination-based CEF-based marking. All packets from AS 24 destined to customer AS 73 will be marked with IP precedence flash.

QPPB marking is only available in combination with CEF switching. The global ip cef command enables CEF switching on all interfaces that support CEF.

The following configuration is used on the NAP router to configure CEF packet marking:

ip cef interface hssi 0/0 bgp-policy destination ip-prec-map

Was this article helpful?

0 0

Post a comment