Does tcp work between clouds in GNS3 via veth?

Question

linux

Good afternoon.
I want to drive my traffic in order to load the GNS3 device (hub type device). For this purpose, I connected my interfaces to the clouds (interfaces on the same network, so I used netnts) and let traffic through the piece of iron. ping between devices goes - nothing else (
I assembled the scheme.
(netns A) vethA - vethB - ​​CLOUD1_GNS3 -----CLOUD2_GNS3 - vethC - vethD(netns D).
I can drive pings between devices. Arp requests go. But on telnet and so on, no one answers. It feels like everything is being cut. But in iptables everything passes. On the sniffer, you can see that it is trying to establish a tcp connection - but no one answers. I tried to turn on the virtual cisco router as a client - to eliminate the problem of my machine - but the same garbage