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sjwrick
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Why is a subnet /30 routing when gw is disabled?

Wed Feb 05, 2025 1:15 am

In ROS7, I want to summarize a network 100.100.0.0/16 instead of advertising each /30 route of my clients. If I have 200 clients that contributes significantly to the routing table across my BGP network, I don’t want to advertise each /30 route for each client across every tower.

For example, client subnets are 100.100.1.0/30, 100.100.2.0/30, and 100.100.3.0/30. The .1 of each /30 is on my router, and the clients have .2 of the subnet on their TPLink routers with DHCP set on the WAN.

In /ip/firewall/address-list, I can list the network 100.100.0.0/16 instead of 100.100.1.0/30, 100.100.2.0/30, and 100.100.3.0/30. I set 100.100.0.1/16 on the customer bridge to facilitate BGP advertisement. I know it is unusual to have 100.100.0.1/16 and 100.100.1.1/30 (etc) on the same bridge. Works though.

In ROS6, I disabled the customer subnet on the router to prevent routing, thus a disabled client. No gateway no route. However, in ROS7, disabling the customer subnet doesn’t disable the client. The rest of the network towers route to the specific router, but why does the customer (TPLink router) route out? Their gateway is gone.

Why does the customer router routes out in ROS7?

Setting up a GNS3 simulation to test this........
 
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panisk0
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Re: Why is a subnet /30 routing when gw is disabled?

Wed Feb 19, 2025 12:57 pm

add 100.100.0.0/16 in routing table as blachole & redistribute via bgp static
/ip route add blackhole dst-address=100.100.0.0/16
/routing/bgp/connection/set output.redistribute=static