Thursday, February 25, 2021

Stating route to cable modem causes ARP (CM600/ER-X)

Hello,

I'm trying to add a static route for my cable modem (Netgear CM600) on my router (ER-X) . I do that so I can advertise it over a BGP session I have, without it, BGP won't advertise the route since the link isn't in the local routing table.

Weirdly, when I add the static route, even tho it has a /32 CIDR, it causes all outgoing traffic to try to ARP request instead of forwarding the traffic.

I suspect it's because of the inactive link that the modem leaves on initial DHCP.

I'm trying to figure out how I can create this static link without everything becoming ARP(ed)?

Some routing excerpts:

A normal connection, with everything working properly (and WITHOUT my static link):

S > 0.0.0.0/0 [210/0] via 192.168.100.1 inactive

*> [210/0] via MY_ISP_IP, eth1

Adding the static route produces the following:

S *> 0.0.0.0/0 [210/0] via 192.168.100.1 (recursive is directly connected, et

h0) )

*> [210/0] via MY_ISP_IP, eth1

S *> 192.168.100.1/32 [1/0] is directly connected, eth1

Ideas why that routing entry would cause everything to ARP? I am guessing the word 'recursive' is the culprit.



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