How to Announce Network to Specific Neighbor Peer in BGP – Cisco Nexus Routing

bgpciscocisco-nexusrouting

I have following scenario where i already have 10G (A – BLUE Link) connectivity from ISP on SW1 and SW2 for redendency and i have configured eBGP and iBGP, Everything is good at this point, Now my company need more bandwidth and more public ips so we ask for another 10G link to our ISP which is B (RED Link) as per following diagram.

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I have following configuration at present with BLUE link peer ( because i didn't configure RED link yet)

router bgp 200
  router-id 192.168.255.20
  log-neighbor-changes
  address-family ipv4 unicast
    network 74.100.100.0/23
    redistribute static route-map RTBH
  neighbor 74.1.1.10
    remote-as 100
    timers 10 30
    address-family ipv4 unicast
      send-community
  neighbor 192.168.255.19
    remote-as 200
    update-source loopback0
    address-family ipv4 unicast
      next-hop-self

Question

Once i configure link (B) RED on SW1 & SW2 then how do i announce my new public subnet B for neighbor B peer?

My link B public subnet is 74.20.20.0/23 how do i tell BGP account it on link B ?

Best Answer

Here is a generic example:

ip prefix-list TO-A seq 10 permit 74.100.100.0/23 le 32
! 
ip prefix-list TO-B seq 10 permit 74.20.20.0/23 le 32 ! the 'le 32' allows smaller subnets of that block
!
router bgp 200
  neighbor <A>
    ip prefix-list TO-A out
  neighbor <B>
    ip prefix-list TO-B out
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