Networking

VRF (Virtual Routing and Forwarding) is like a logical router, no need to require many router for different routing or different customers.VRF are most commonly associated MPLS service providers. Deployment without MPLS is know as VRF lite.In this topology we configure the VRF Lite. Let see, we have two customer Green and Yellow are using our network service.They have same network prefixes. As we know router don't accept same network prefixes but Vrf can solve that problem. First step we need to create vrf. R1 ip vrf GREEN ip vrf YELLOW R2 ip vrf GREEN ip vrf YELLOW R3 ip vrf GREEN ip vrf YELLOW Each routed interface (virtual or physical) belongs to exactly one VRF.  For vrf GREEN R2 int lo0 ip vrf forwarding GREEN ip add 192.168.1.1 255.255.255.0 int f0/0.1 encapsulation dot1q 10 ip vrf forwarding GREEN ip add 10.10.12.2 255.255.255.252 R1 int f0/0.1  encapsulation dot1Q 10  ip vrf forwarding GREEN  ip address 10.10.12.1 255.255.255.252 int

In this scenario I want to filter 192.168.3.x /25 , /26, /27 networks form R1 route update. I can use access list but I need to set the rules for every network. In prefix list it will easy to filter. R2(config-router)#do sh ip bgp BGP table version is 8, local router ID is 2.2.2.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,               r RIB-failure, S Stale Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 192.168.1.0      10.10.10.1               0             0 1 i *> 192.168.2.0      10.10.10.1               0             0 1 i *> 192.168.3.0/25   10.10.10.1               0             0 1 i *> 192.168.3.128/26 10.10.10.1               0             0 1 i *> 192.168.3.192/27 10.10.10.1               0             0 1 i *> 192.168.4.0/25   10.10.10.1               0             0 1 i *> 192.168.4.128/26 10.10.10.1               0   

In this scenario R1 connect R2 with different bandwidth line. If we can't change EIGRP 'k' values, bandwidth and delay on the existing interfaces and only involve EIGRP, offset list is the way to solve this cause. Now R1 know only one route to 3.3.3.0/24 network. R1#sh ip route eigrp      3.0.0.0/24 is subnetted, 1 subnets D       3.3.3.0 [90/3142400] via 10.10.12.2, 00:48:21, Serial0/0      10.0.0.0/24 is subnetted, 3 subnets D       10.10.23.0 [90/3014400] via 10.10.12.2, 00:53:18, Serial0/0 We see R1 have only one path to 3.3/14 network. Now I will set offset list on R2. First I need to check R1 metric value for 3.3.3.0/24 network. R1#sh ip eigrp top IP-EIGRP Topology Table for AS(123)/ID(1.1.1.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,        r - reply Status, s - sia Status P 1.1.1.0/24, 1 successors, FD is 128256         via Connected, Loopback0 P 3.3.3.0/24, 1 successors, FD is 3142400         via 10.10.12.2 ( 3142400/ 15616