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Garreth McDaid
Asked: 2014-08-29 05:11:48 +0800 CST

Can I add an extra route to my Amazon VPC?

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I have an Amazon VPC set up between AWS and my corporate LAN.

Originally, when I set it up, I specified static routing for the following CIDRs:

10.55.55.0/24 10.77.77.0/24 10.99.99.0/24

I set up the following CIDR in the VPC:

10.44.0.0/16

This all worked fine.

I now have a new network on my Corporate LAN: 10.55.54.0/24

I added a new route in the main routing table for this, pointing to the same vgw as the others.

When I know look at the routes, I see that the original 3 routes are propagated, but the 4th new one is not.

On a server instance in 10.44.0.0/16, I can still connect to hosts in the existing 3 CIDRs, but I am not seeing any routing for the new CIDR:

[server]$ traceroute 10.55.55.88
traceroute to 10.55.55.88 (10.55.55.88), 30 hops max, 60 byte packets
1  169.254.254.37 (169.254.254.37)  0.543 ms  0.524 ms  0.504 ms
2  169.254.254.5 (169.254.254.5)  1.278 ms  1.007 ms  0.985 ms
3  169.254.254.2 (169.254.254.2)  32.596 ms 169.254.254.6 (169.254.254.6)  35.244 ms     169.254.254.2 (169.254.254.2)  32.830 ms
4  ip-10-55-55-88.eu-west-1.compute.internal (10.55.55.88)  36.822 ms  37.338 ms  36.842 ms


[server]$ traceroute 10.55.54.88
traceroute to 10.55.54.88 (10.55.54.88), 30 hops max, 60 byte packets
<timeout>

What step am I missing here? Do I have to recreate the entire VPC/VPN to include the new CIDR?

amazon-vpc

1 Answers

  1. Best Answer

    You do not need to add a route into any routing table for this to work. It can be accomplished in a few steps in the console

    1. Go to "VPN Connections", select the connection for your corporate LAN, go to the "Static Routes" tab and add the new IP subnet
    2. Go to "Route Tables", select the table you want to modify, go to the "Route Propagation" tab and insure the Virtual Private Gateway for your corporate LAN is checked
    3. Insure that the route table modified in the previous step is associated with the subnets you want ("Subnets", select a subnet, "Route Table")

    Note: You can only have one route table associated with a subnet at a time. If you have changed the route table from the main routing table to a custom one, you will need to insure that route table has route propagation enabled for your virtual private gateway.

    Additional things to check:

    • Be sure that routes are setup appropriately on your corporate LAN so that packets from the new IP subnet to the VPC subnet will be appropriately routed via your customer gateway
    • Insure that if you were filtering packets on your customer gateway you enable packets with the new IP subnet as the source.

    As always review the Amazon Virtual Private Cloud documentation.

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