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I would need to configure a cross connect between two VPC networks via SFP Fiber. Unfortunately I'm new on BGP configuration and would need confirmation that I'm doing it on the right way...

I have Two VPC:

VPC A: ASN 200 IP Router: 169.254.250.1 Sub Network: 10.0.0.1/34

VPC B: ASN 100 IP Router: 169.254.250.2 linked with 4 Servers: 169.254.131.1 / 169.254.131.2 / 169.254.131.3 / 169.254.131.4

VPC A is completely configured, I purchased a Cisco router C1113-8PM to configure my VPC B. My aim is to ensure that any server on VPC A can access my 4 servers located in VPC B through BGP.

The procedure I started to write into VPC B Router:

#Configure ASN VPC B on Router
enable
configure terminal
router bgp 100
bgp router-id 169.254.250.2
timers bgp 70 120
end

# Configure ASN VPC A and routes
configure terminal
neighbor 169.254.250.1 remote-as 200
address-family ipv4 unicast
neighbor 169.254.250.1 activate
end

is it enough ? Do I need to set each IP address of my VPC B into BGP table ?

Concerning IP Configuration, I just set each interface with my local server IP:

ip routing
bridge 1 protocol dec
no clns routing
!
interface GigabitEthernet0/0/0
ip address 169.254.131.1 255.255.0.0
!
interface GigabitEthernet0/1/0
ip address 169.254.131.2 255.255.0.0
!
interface GigabitEthernet0/1/1
ip address 169.254.131.3 255.255.0.0
bridge-group 1
!
interface GigabitEthernet0/1/2
ip address 169.254.131.4 255.255.0.0
bridge-group 1
!
interface GigabitEthernet0/1/3
!
interface GigabitEthernet0/1/4
!
interface GigabitEthernet0/1/5
!
interface GigabitEthernet0/1/6
!
interface GigabitEthernet0/1/7
!
interface ATM0/2/0
ip address 169.254.250.2 255.255.0.0
bridge-group 1
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  • 1
    Remember that you cannot route packets with link-local addresses in the 169.254.0.0/16 network. That is one of the IPv4 special address ranges that is reserved by IPv4 itself, and is not forwardable. Link-local means it is confined to a single link.
    – Ron Maupin ♦
    Apr 8, 2022 at 12:25
  • "7. Router Considerations A router MUST NOT forward a packet with an IPv4 Link-Local source or destination address, irrespective of the router's default route configuration or routes obtained from dynamic routing protocols."
    – Ron Maupin ♦
    Apr 8, 2022 at 17:16
  • Also, you cannot subnet the 169.251.0.0/16 range. "2.8. Link-Local Packets are Local The non-forwarding rule means that hosts may assume that all 169.254/16 destination addresses are "on-link" and directly reachable. The 169.254/16 address prefix MUST NOT be subnetted. This specification utilizes ARP-based address conflict detection, which functions by broadcasting on the local subnet. Since such broadcasts are not forwarded, were subnetting to be allowed then address conflicts could remain undetected."
    – Ron Maupin ♦
    Apr 8, 2022 at 17:21

1 Answer 1

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Your BGP router needs to advertise its networks to VPC A. You can either redistribute a static route or redistribute connected interfaces, depending on your topology.

I want to also mention that the 169.254.0.0/16 network is designated a link local subnet only. It is not intended to be advertised to other routers and many consider it poor practice to do so.

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8
  • You are of course about 169.254.0.0/16 , the fact is AWS choosed to use it to pick /30 network for routing inside VPN tunnels (albeit you are not forced to use it).
    – JFL
    Apr 8, 2022 at 12:28
  • Yes, and I have configured AWS tunnels. But you don't have to advertise that link anywhere.
    – Ron Trunk
    Apr 8, 2022 at 12:33
  • ouch...my servers IP are already set....quite difficult to change them now....Hopefully we are not hosted by AWS....
    – tiamat
    Apr 8, 2022 at 12:33
  • when you say redistribute connected interface or static route, what is the difference ? I configured each connected interfaces with their respective IP Address, and I would need to use "ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name]" ?
    – tiamat
    Apr 8, 2022 at 12:35
  • 1
    The simplest (but may not be the best) way is to add redistribute connected under the address-family ipv4.
    – Ron Trunk
    Apr 8, 2022 at 13:10

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