Can access host only if I PING

Issues related to configuring your network
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Can access host only if I PING

Post by Terry_Roman » 2018/10/09 16:38:29

Hi all, I have network issue, I can access centos 7 x64 host only if I start ping. If ping is off host is not accesable on any port. If I first ping Host then evrything works, HTTP, ssh, telnet.
It's a local network, internet is working, firewalld is disabled, selinux disabled.
There is only 2 hosts have eccess without ping, my dns server and gateway host.
This two hosts listed in network config and I think this is a reason why they have access without ping.
Thank you in advance.

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Re: Can access host only if I PING

Post by hunter86_bg » 2018/10/10 17:38:48

This sounds like your switch's CAM table gets empty, and once you ping, the switch broadcasts the ICMP echo request on all ports and once the CentOS 7 responds - you get your connection requests properly.

This is just a guess.
In order to verify that, run tcpdump on the CentOS and then try to connect via ssh/http or any other service on your CentOS. If the CentOS doesn't respond , but a package is received you have to check local firewall and ignore my "guess".

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Re: Can access host only if I PING

Post by TrevorH » 2018/10/10 20:33:44

Also post the ifcfg file for the interface from your CentOS box as the networking is meant to use arp to tell the switch it exists as it boots.
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