3.7.d Implement, optimize and troubleshoot routing policies

3.7.d [i] Attribute manipulation

questions, comments: arteq_2015@outlook.com

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bgp_med_always-compare-med

begin with the IGP; verify connectivity.

R1#sh cdp neigh det | i Device|IP
Device ID: R2
IP address: 192.168.12.2
Device ID: R3
IP address: 192.168.13.3

configure eigrp 100; include ONLY the directly connected networks, and loopback ZERO’s.

R1(config-router)#do sh ip route eigrp
2.0.0.0/24 is subnetted, 1 subnets
D       2.2.2.0 [90/156160] via 192.168.12.2, 00:00:53, FastEthernet0/0
3.0.0.0/24 is subnetted, 1 subnets
D       3.3.3.0 [90/156160] via 192.168.13.3, 00:00:26, FastEthernet1/0
R1(config-router)#

configure BGP for 65001; use the lo0‘s as update sources; ONLY advertise the loopbacks that are NOT lo0.

bgp_med_sh_bgp

configure R2 to send a metric of 200 for it’s advertised networks.

configure R3 to send a metric of 300 for it’s advertised networks.

either clear bgp or wait for rapture.

bgp_med_01

swap the metric values between R2 and R3. note that R1 now prefers the 100 network of R3, and the metric values of the other two networks have also changed.

bgp_3net_preferred.

specify that R2 and R3 send these metrics for the 100 network ONLY.

bgp_med_w_acl

note the 0 metrics for the 2 and 3 networks.

swap the metrics back so that R2 is again preferred by R1 for the 100 network, but this time use a network statement in BGP; no acl’s allowed.

bgp_med_net_statement

IBGP will always adhere to the metric set within it’s confines. if a better metric is set by EBGP, it will be ignored, unless… this is the point of always-compare-med…