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prepare the config as below R1 interface Loopback0 ip address 10.10.10.1 255.255.255.255 ! interface Loopback1 ip address 10.239.1.1 255.255.255.0 ! interface Loopback2 ip address 10.239.2.1 255.255.255.0 ! interface Loopback3 ip address 10.239.3.1 255.255.255.0 ! interface Loopback4 ip address 10.239.4.1 255.255.255.0 ! interface Loopback5 ip address 10.239.5.1 255.255.255.0 ! interface Loopback6 ip address 10.239.6.1 255.255.255.0 ! interface Loopback7 ip address 10.239.7.1 255.255.255.0 ! interface Loopback8 ip address 10.239.8.1 255.255.255.0 ! interface Loopback9 ip address 10.239.9.1 255.255.255.0 ! interface Serial0/0 bandwidth 128 ip address 10.1.12.1 255.255.255.252 clock rate 128000 ! interface Serial0/1 bandwidth 128 ip address 10.1.13.1 255.255.255.252 clock rate 128000 ! router eigrp 1 network 10.1.0.0 0.0.255.255 network 10.10.10.1 0.0.0.0 network 10.239.0.0 0.0.255.255 no auto-summary R2 interface Loopback0 ip address 10.10.10.2 255.255.255.255 ! interface FastEthernet0/0 ip address 10.151.1.1 255.255.255.0 duplex auto speed auto ! interface Serial0/0 bandwidth 128 ip address 10.1.12.2 255.255.255.252 ! router eigrp 1 network 10.1.12.2 0.0.0.0 network 10.10.10.2 0.0.0.0 network 10.151.1.0 0.0.0.255 no auto-summary R3 interface Loopback0 ip address 10.10.10.3 255.255.255.255 ! interface FastEthernet0/0 ip address 10.151.1.3 255.255.255.0 duplex auto speed auto ! interface Serial0/0 bandwidth 128 ip address 10.1.13.2 255.255.255.0 ! interface FastEthernet0/1 ip address 10.232.1.3 255.255.255.0 duplex auto speed auto ! router eigrp 1 network 10.1.13.2 0.0.0.0 network 10.10.10.3 0.0.0.0 network 10.151.1.0 0.0.0.255 network 10.232.1.0 0.0.0.255 no auto-summary ---------------------------------------------------------------------- let's get started.. ROUTING TABLE !! start with 'sh ip route' on R1 make sure you can see all route below 10.0.0.0/8 is variably subnetted, 17 subnets, 3 masks C 10.1.13.0/30 is directly connected, Serial0/1 D 10.1.13.0/24 [90/21026560] via 10.1.12.2, 07:02:08, Serial0/0 C 10.1.12.0/30 is directly connected, Serial0/0 D 10.10.10.2/32 [90/20640000] via 10.1.12.2, 00:00:52, Serial0/0 D 10.10.10.3/32 [90/20640000] via 10.1.13.2, 00:00:52, Serial0/1 C 10.10.10.1/32 is directly connected, Loopback0 D 10.151.1.0/24 [90/20514560] via 10.1.12.2, 00:00:52, Serial0/0 [90/20514560] via 10.1.13.2, 00:00:52, Serial0/1 C 10.239.5.0/24 is directly connected, Loopback5 C 10.239.4.0/24 is directly connected, Loopback4 C 10.239.7.0/24 is directly connected, Loopback7 C 10.239.6.0/24 is directly connected, Loopback6 D 10.232.1.0/24 [90/20514560] via 10.1.13.2, 00:00:53, Serial0/1 C 10.239.1.0/24 is directly connected, Loopback1 C 10.239.3.0/24 is directly connected, Loopback3 C 10.239.2.0/24 is directly connected, Loopback2 C 10.239.9.0/24 is directly connected, Loopback9 C 10.239.8.0/24 is directly connected, Loopback8 basically, from the diagram, you can see that from R1 there are two routes to all the network that connected to R2 and R3, but from the routing table.. only network 10.151.1.0 have two routes actually only one and the best route installed into Routing Table, that explain why there's only one route for every network ..EXCEPT 10.151.1.0.. ok, that's is because this network has a same metric value, so routing table install both.. so, which route R1 will pick to go to that network.. well.. (I haven't figured it out yet, ha2. why don't u figured it out) EIGRP TOPOLOGY TABLE there's another table storing the routing information.. SHOW IP EIGRP TOPO, remember. Only EIGRP has this !! EIGRP store all the available routing path inside this table .... P 10.1.12.0/30, 1 successors, FD is 20512000 via Connected, Serial0/0 P 10.10.10.2/32, 1 successors, FD is 20640000 via 10.1.12.2 (20640000/128256), Serial0/0 via 10.1.13.2 (20642560/156160), Serial0/1 P 10.10.10.3/32, 1 successors, FD is 20640000, U via 10.1.13.2 (20640000/128256), Serial0/1 via 10.1.12.2 (20642560/156160), Serial0/0 P 10.10.10.1/32, 1 successors, FD is 128256 via Connected, Loopback0 P 10.151.1.0/24, 2 successors, FD is 20514560, U via 10.1.13.2 (20514560/28160), Serial0/1 via 10.1.12.2 (20514560/28160), Serial0/0 P 10.239.5.0/24, 1 successors, FD is ... notice that if a network have two routes(blue), only the smallest metric(or cost) make it to the routing table(green).. unless all the route has the same value. there's a term for this
let's adjust some the metric, there's a few method to do this let's start with OFFSET-LIST to modify metric of routes that learned thru particular interface, what we gonna do is, add metric value of 10000 on R1 for every route learned via serial 0/1 R1(config)#router ei 1 R1(config-router)#offset-list 22 in 10000 serial 0/1 by right, now only one route to 10.151.1.0 installed into ROUTING TABLE because one of the interface configured to have additional metric 10000, SHOW IP ROUTE C 10.10.10.1/32 is directly connected, Loopback0 D 10.151.1.0/24 [90/20514560] via 10.1.12.2, 00:00:35, Serial0/0 C 10.239.5.0/24 is directly connected, Loopback5 SHOW IP TOPO to confirm the value now is different, compare the metric value for every route learn via serial 0/1 (compare with previous EIGRP topology table on top of the page) all have extra 10000 P 10.10.10.2/32, 1 successors, FD is 20640000 via 10.1.12.2 (20640000/128256), Serial0/0 via 10.1.13.2 (20652560/166160), Serial0/1 P 10.10.10.3/32, 1 successors, FD is 20640000 via 10.1.12.2 (20642560/156160), Serial0/0 via 10.1.13.2 (20650000/138256), Serial0/1 P 10.10.10.1/32, 1 successors, FD is 128256 via Connected, Loopback0 P 10.151.1.0/24, 1 successors, FD is 20514560 via 10.1.12.2 (20514560/28160), Serial0/0 via 10.1.13.2 (20524560/38160), Serial0/1 but remember, this only apply one way only, for example in this config, only R1 see the different.. there's no affect on route learned by R2 and R3. but you still can modify the outgoing traffic just replace IN with OUT in the command |
Tuesday, September 21, 2010
EIGRP metric
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