Can a TGW route with same destination CIDR block have more than one TGW Attachment?

The API schema to retrieve TGW Routes for a particular route table returns list of destination CIDR blocks each having a list of TGW Attachments - mentioning resource type and ID. Here's the reference - https://docs.aws.amazon.com/cli/latest/reference/ec2/search-transit-gateway-routes.html

It'd be helpful if one can share a sample topology where multiple attachments come under same destination CIDR block? How does routing happen in this case as the next hop type can be different for the same IP to be routed?

Aniket
10 個月前
Also, if you try creating a route with same destination CIDR, it throws an error: "Route <CIDR> already exists in Transit Gateway Route Table <table-ID>"
Toni_S 專家
10 個月前
You are referring to V1 documentation of the CLI, are using V1 of the CLI or V2 which is the latest? It has up to date documentation located at: https://awscli.amazonaws.com/v2/documentation/api/latest/reference/ec2/search-transit-gateway-routes.html

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Aniket

已提問 10 個月前檢視次數 368 次

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TransitGatewayAttachments list in CLI response can have multiple attachments if you have multiple VPN connections with with BGP and ECMP is enabled. Then it would list all of the VPN connection attachments there.

jose

已回答 10 個月前

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Toni_S

已審閱 10 個月前

Toni_S 專家

10 個月前

Here's an example what an entry would look like the scenario mentioned above.

    "Routes": [
        {
            "DestinationCidrBlock": "10.0.0.0/24",
            "TransitGatewayRouteTableAnnouncementId": "",
            "TransitGatewayAttachments": [
                {
                    "ResourceId": "vpn-XXXXXXXXXX(xx.xx.xx.xx)",
                    "TransitGatewayAttachmentId": "tgw-attach-XXXXXXXXXX",
                    "ResourceType": "vpn"
                },
                {
                    "ResourceId": "vpn-YYYYYYYYYY(yy.yy.yy.yy)",
                    "TransitGatewayAttachmentId": "tgw-attach-YYYYYYYYYY",
                    "ResourceType": "vpn"
                }
            ],
            "Type": "propagated",
            "State": "active"
        }

I can't see a case where multiple attachments come under same destination CIDR block. I think it's a List to neatly handle the fact that there isn't always one attachment - there can zero or one. A Blackhole route will have zero attachments.

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skinsman

已回答 10 個月前

Can a TGW route with same destination CIDR block have more than one TGW Attachment?

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