New User - Internet connectivity issue - CentOS7 VM

Issues related to configuring your network
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manwine
Posts: 2
Joined: 2020/11/01 17:56:35

New User - Internet connectivity issue - CentOS7 VM

Post by manwine » 2020/11/01 18:03:26

Hi everyone,
I'm relatively new to server use and I'm working on a project for school, I got deep into it, had my second cent server set up as a print server etc however I've only now realized that my internet services aren't working like they should.

I tried everything to correct the issue but I couldn't diagnose it so I closed them and started a fresh VM installation. I set my ip, dns, host info at start up but this new machine is doing the same thing.

I can ping my gateway and 8.8.8.8 but can't resolve the host when pinging google.ca. Firefox won't connect to sites and I can't update services through shell.

So it's a DNS issue right? I don't know what's incorrect in my settings.

ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.208.10 netmask 255.255.255.0 broadcast 192.168.208.255


default via 192.168.208.2 dev ens33 proto static metric 100
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
192.168.208.0/24 dev ens33 proto kernel scope link src 192.168.208.10 metric 100


# Generated by NetworkManager
search tdm.osys3030.ca
nameserver 8.8.8.8

Everything seems fine. gateway set, dns using google's, I'm at my wit's end. Anyone know what the issue could be?

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jlehtone
Posts: 3172
Joined: 2007/12/11 08:17:33
Location: Finland

Re: New User - Internet connectivity issue - CentOS7 VM

Post by jlehtone » 2020/11/01 23:21:35

You have a VM connected to subnet 192.168.208.0/24 with address 192.168.208.10.
The 192.168.208.2 is a router between that subnet and other subnets.
You can ping the router and an address (8.8.8.8) behind the router, but you can't get DNS reply from 8.8.8.8.

If you have command 'host' or 'dig', then you can tell them to use 8.8.8.8 as server for test query (i.e. ignore the /etc/resolv.conf).
They might tell "can't reach DNS server" differently than 'ping' does.

You have a VM. Is it possible that the virtualization platform has firewall rules that restrict your access?

manwine
Posts: 2
Joined: 2020/11/01 17:56:35

Re: New User - Internet connectivity issue - CentOS7 VM

Post by manwine » 2020/11/02 13:21:05

[jbeau@wbrm0101 ~]$ dig 8.8.8.8

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-16.P2.el7_8.6 <<>> 8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 32477
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;8.8.8.8. IN A

;; AUTHORITY SECTION:
. 86397 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2020110200 1800 900 604800 86400

;; Query time: 45 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Nov 02 09:18:56 AST 2020
;; MSG SIZE rcvd: 111

[jbeau@wbrm0101 ~]$ dig google.ca

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-16.P2.el7_8.6 <<>> google.ca
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18772
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;google.ca. IN A

;; ANSWER SECTION:
google.ca. 299 IN A 172.217.13.163

;; Query time: 65 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Nov 02 09:19:16 AST 2020
;; MSG SIZE rcvd: 54

[jbeau@wbrm0101 ~]$


I don't believe it's a firewall issue as I can use my vm's for other courses normally.

User avatar
jlehtone
Posts: 3172
Joined: 2007/12/11 08:17:33
Location: Finland

Re: New User - Internet connectivity issue - CentOS7 VM

Post by jlehtone » 2020/11/02 20:51:26

manwine wrote:
2020/11/02 13:21:05
$ dig google.ca
...
;; ANSWER SECTION:
google.ca. 299 IN A 172.217.13.163

;; Query time: 65 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
Ok, you can resolve "google.ca". Therefore, name resolution should not be the issue? How did you fail?

Google does most likely have some load balancing and therefore I get different number:

Code: Select all

$ host google.ca 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

google.ca has address 216.58.207.195
google.ca has IPv6 address 2a00:1450:400f:80b::2003
google.ca mail is handled by 50 alt4.aspmx.l.google.com.
google.ca mail is handled by 20 alt1.aspmx.l.google.com.
google.ca mail is handled by 10 aspmx.l.google.com.
google.ca mail is handled by 30 alt2.aspmx.l.google.com.
google.ca mail is handled by 40 alt3.aspmx.l.google.com.

$ host 216.58.207.195 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

195.207.58.216.in-addr.arpa domain name pointer arn11s04-in-f3.1e100.net.

$ host 172.217.13.163 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

163.13.217.172.in-addr.arpa domain name pointer yul03s04-in-f3.1e100.net.
How about:

Code: Select all

sudo yum repolist all
That command has to resolve names and access http-servers. You get errors?


The default network config system in CentOS 7 is NetworkManager.service
You get summary with plain nmcli
List of devices: nmcli d s (shorthand for 'nmcli device state')
List of connections: nmcli c s (shorthand for 'nmcli connection show')
If the name of your connection is "ens33", then

Code: Select all

nmcli c s ens33
shows both persistent configuration and current, active config of that connection.

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