Is there a chance that an IP packet with the the same source and destination IP can get further to the network?

Question

I have recently run into a discussion on this topic, and I think there is a need for some more detailed technical answer.

I want to ask this simple and basic question:

When I configure a service on an IP network host (http, ftp, dns, etc.), e.g. 10.0.0.11 and I access the service from the same host with the IP address of one network interface (not with 127.0.0.1 - loopback, but 10.0.0.11), is there any chance that the IP packets with the sourceIP=destinationIP=10.0.0.11 get anywhere beyond the local network interface?

(So when there is a problem with the switch or router it could cause my service ftp://10.0.0.11 (dns ...) to become unavailable from a browser running on 10.0.0.11)?

Answer 1

There might arise a challenge not from the packet itself -- as you ask in your question -- but from additional requests that the webserver starts in order to start-up (see this Apache page) or even worse to deliver each single response. The problem is based on a reverse DNS lookup. So, when your host is disconnected this might lead to a bad or no service ... caused by the webserver waiting for a DNS timeout or rejecting replies when the lookup cannot be done.