Direct Connect offering though it connects to AWS has a difference in operation depending on the VIF we connect.

Public VIF

→ So when we have this setup, this is in no way related to VPC at all, all this does is advertise Amazon-owned Public Prefixes for services like S3/EC2(Elastic-IP only, not your Private IP), and that's all to it.

→ There is flexibility at the customer end to scope the advertisement propagation t LOCAL, CONTINENT, and GLOBAL levels within AWS in an outbound direction and has the flexibility to filter in bound updates which are advertised toward him.

Here is by default, how the Community scope looks like, you also have the flexibility to filter routes inbound to customers.

Note: Outbound communities restrict the advertisement of prefixes to region/continent/global scope for any sort of Any-cast implementations.

if Customer sends route with community

7224:9100 → This will be local to the region

7224:9200 → This will be local to the continent, ie scope is till EU

7224:9300 → Global, by default its global even if you don’t export with this community

How to Verify -

• The easiest way is to advertise your public-routes and ping from the EC2 host in the region, depending on the community you will have reachability from Region/Continent or entire AWS Global regions.

Sample output from the routers on how prefixes would look in case of a Public VIF

lab-router#show ip bgp summary
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
x.x.240.241  4         7224      93      44    90205    0    0 00:18:06     8024

lab-router#show ip route

      2.0.0.0/24 is subnetted, 2 subnets
B        2.255.190.0 [20/10] via x.x.240.241, 00:18:12
B        2.255.191.0 [20/10] via x.x.240.241, 00:18:11
      3.0.0.0/8 is variably subnetted, 244 subnets, 10 masks
B        3.0.0.0/15 [20/10] via x.x.240.241, 00:18:12
B        3.2.0.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.2.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.3.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.8.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.9.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.10.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.11.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.12.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.13.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.14.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.15.0/24 [20/10] via x.x.240.241, 00:18:12
B        3.2.48.0/24 [20/10] via x.x.240.241, 00:18:12
...