Lab10 MPLS + Same RD + Add-Path + UCMP

Load lab9.init.cfg

#R1, R6
configure replace unix:lab9.init.cfg

#R2-R5, R7
configure
load bootflash:lab10.init.cfg
commit replace
y

Using the previous config from lab 9, reconfigure the RDs so that they are all the same value. Use Add-Path to achieve load balancing on R2 again.

Answer

#R2
router bgp 65000
 address-family vpnv4 unicast
  additional-paths receive
 !
 address-family vpnv6 unicast
  additional-paths receive
 !
 no vrf CUST_A
 
** commit **

router bgp 65000
 vrf CUST_A
  rd 100:100
  address-family ipv4 unicast
   maximum-paths ibgp 2
  !
  address-family ipv6 unicast
   maximum-paths ibgp 2
  !
  neighbor 10.1.2.1
   remote-as 65001
   address-family ipv4 unicast
    route-policy PASS in
    route-policy PASS out
   !
  !
  neighbor fc00:10:1:2::1
   remote-as 65001
   address-family ipv6 unicast
    route-policy PASS in
    route-policy PASS out

#R4
router bgp 65000
 no vrf CUST_A
 
** commit **

router bgp 65000
 vrf CUST_A
  rd 100:100
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !
  neighbor 10.4.6.6
   remote-as 65006
   dmz-link-bandwidth
   address-family ipv4 unicast
    route-policy PASS in
    route-policy PASS out
   !
  !
  neighbor fc00:10:4:6::6
   remote-as 65006
   dmz-link-bandwidth
   address-family ipv6 unicast
    route-policy PASS in
    route-policy PASS out

#R5
router bgp 65000
 no vrf CUST_A
 
** commit **

router bgp 65000
 vrf CUST_A
  rd 100:100
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !
  neighbor 10.5.6.6
   remote-as 65006
   dmz-link-bandwidth
   address-family ipv4 unicast
    route-policy PASS in
    route-policy PASS out
   !
  !
  neighbor fc00:10:5:6::6
   remote-as 65006
   dmz-link-bandwidth
   address-family ipv6 unicast
    route-policy PASS in
    route-policy PASS out

#R7
route-policy SELECT_BACKUP
  set path-selection backup 1 advertise
end-policy
!
router bgp 65000
 address-family vpnv4 unicast
  additional-paths send
  additional-paths selection route-policy SELECT_BACKUP
 !
 address-family vpnv6 unicast
  additional-paths send
  additional-paths selection route-policy SELECT_BACKUP
  
 do clear bgp *

Explanation

R7 now receives all routes with an RD of 100:100. R7 must use Add-Path to select a second backup route and send this to R2. Otherwise, R7 hides information because it selects only a single bestpath among all identical routes with the same RD.

R2 is still able to do UCMP: