DNS Cache Flush needed on Plusnet side

[#1]

Most likely slack had to do something with this too but I am finding that from the 5 DNS servers Plusnet is providing only one works on slack.com NS queries.

https://www.plus.net/help/broadband/about-dns-server-and-website-settings/

Please flush the caches on the Plusnet hosted DNS servers.

See bellow:

dig @212.159.13.49 status.slack.com

; <<>> DiG 9.10.6 <<>> @212.159.13.49 status.slack.com

; (1 server found)

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 13103

;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

;; QUESTION SECTION:

;status.slack.com. IN A

;; Query time: 17 msec

;; SERVER: 212.159.13.49#53(212.159.13.49)

;; WHEN: Fri Oct 01 07:55:05 BST 2021

;; MSG SIZE  rcvd: 45

Only the safeguard server is working correctly:

dig @213.120.234.42 status.slack.com

; <<>> DiG 9.10.6 <<>> @213.120.234.42 status.slack.com

; (1 server found)

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61846

;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 512

;; QUESTION SECTION:

;status.slack.com. IN A

;; ANSWER SECTION:

status.slack.com. 60 IN CNAME slack-status.azureedge.net.

slack-status.azureedge.net. 925 IN CNAME slack-status.ec.azureedge.net.

slack-status.ec.azureedge.net. 925 IN CNAME scdn1.wpc.80a9c.phicdn.net.

scdn1.wpc.80a9c.phicdn.net. 925 IN CNAME sni1gl.wpc.phicdn.net.

sni1gl.wpc.phicdn.net. 925 IN A 152.199.21.175

;; Query time: 23 msec

;; SERVER: 213.120.234.42#53(213.120.234.42)

;; WHEN: Fri Oct 01 07:56:03 BST 2021

;; MSG SIZE  rcvd: 193

All of these are not working:

To set standard DNS server addresses
Primary	212.159.13.49
Secondary	212.159.13.50
To set alternative DNS server addresses
Primary	212.159.6.9
Secondary	212.159.6.10

[#2]

Hiya @Justinian, I am really sorry for the issue and for the inconvenience this is causing.

Our teams are aware and looking to get this sorted. In the meantime, can you please confirm what device you are using?

[#3]

Hi @LaurenB!

I'm not Justinian, but I believe I'm seeing this issue too. At first I thought it was a general DNS problem, I didn't realise it was only *.slack.com that seems (so far) to have the problem. Querying the DNS from my Plusnet Hub One was (and still is) returning a failure for anything at *.slack.com, other addresses seem unaffected. My Hub One is on 4.7.5.1.83.8.289, if that makes a difference.

Examples below from my MacBook. My Raspberry Pi gives similar results.

% nslookup slack.com 192.168.1.254
Server:        192.168.1.254
Address:    192.168.1.254#53

** server can't find slack.com: SERVFAIL

% nslookup status.slack.com 192.168.1.254
Server:        192.168.1.254
Address:    192.168.1.254#53

** server can't find status.slack.com: SERVFAIL

% nslookup fast.com 192.168.1.254
Server:        192.168.1.254
Address:    192.168.1.254#53

Non-authoritative answer:
Name:    fast.com
Address: 23.55.9.201

% nslookup status.slack.com 1.1.1.1      
Server:        1.1.1.1
Address:    1.1.1.1#53

Non-authoritative answer:
status.slack.com    canonical name = slack-status.azureedge.net.
slack-status.azureedge.net    canonical name = slack-status.ec.azureedge.net.
slack-status.ec.azureedge.net    canonical name = scdn1.wpc.80a9c.phicdn.net.
scdn1.wpc.80a9c.phicdn.net    canonical name = sni1gl.wpc.phicdn.net.
Name:    sni1gl.wpc.phicdn.net
Address: 152.199.21.175

[#4]

We're also having problems accessing slack.com.

I've tried adding slack.com/ to the list of Allowed Websites but it still doesn't load.

I've turned off the firewall to see if that helps, which isn't ideal for security and am currently waiting to see if that fixes things.

My wife needs this for work so please could you make it top priority.

[#5]

@PineMountain That's how I noticed the issue first, when Slack wouldn't work on one computer but would on the other.

The quickest fix in your case is to override the DNS settings on your wife's computer to use a different DNS server (e.g. 1.1.1.1).

If you don't already know how to do that, this seems like a fairly sensible guide: https://www.lifewire.com/how-to-change-dns-servers-in-windows-2626242 (I'm assuming your wife's computer uses Windows)

[#6 · Accepted solution]

I can confirm this is now fixed. It was flagged on their status page as well.

https://status.slack.com/2021-09/06c1e17de93e7dc2

[#7]

Thanks Dabbler - much appreciated.

She works on a Mac and keep track on her Android phone but fingers crossed Justinian is correct and it's been fixed.

[#8]

Looks like Plusnet's DNS servers still need flushing, as far as I can tell.

I had to change the DNS settings on my Mac to get Slack working again.

System Preferences > Network > [choose network from the list on the left] > Advanced… > DNS

[#9]

I'm guessing that they've done the DNS reset as it's working for us now. Hope it's sorted for everyone else too.
Thanks for everyone's help.

[#10]

Hi everyone, I can confirm our back end team confirmed the issue being resolved yesterday afternoon and we haven't heard of any reports since. Should anyone continue to be having issues however then please get back to us and we'll happily investigate further.