Questions tagged [ttl]

Time To Live is a mechanism to prevent messages from traversing the network indefinitely

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Is it necessary to set a different ttl before change a Route53 DNS record value?

The first time create the Route53 DNS record with a load balancer origin DNS name with ttl 1 day. After some days, we want to change the value to another load balancer origin DNS name. Do we need to ...
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How does DNS TTL work in chained CNAME configurations?

I have a DNS config that looks something like this: www.example.com 600 IN CNAME prod.myzone.l2.company.example prod.myzone.l2.company.example 600 IN CNAME ssl-endpoint-...
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Varnish - How can I set TTL in response header?

I have not tried this before on Varnish. And I must admit that my last experience with Varnish was way back - version 2.1.5 days! I have set varnish 6.x as a simple/basic static http-cache. I have ...
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recommended TTLs during Zone transfer

I'm working on transferring zones from DynDNS to Route53, any suggestion on what the TTLs (SOA and NS records) should be - during this transition period (i.e. before/when I update the registrar to ...
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DNS TTL for a record differs between authoritative server, resolver and client

Here's my scenario: I have an office which connects to AWS via a VPN tunnel to access some EC2 instances. The office computers use AWS Route 53 via the VPN tunnel to resolve a private hosted zone. ...
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TTL/UART communication issue

I have (an awesome) Onion Omega2+ SBC and an A9G GPS/GSM module. The module has two UART ports. I can easily read data from the UART_GPS but for some reason I cannot communicate with the UART port for ...
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2 votes
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Ubuntu transmits TTL 0 multicast packets

IP packets with TTL 0 shall not leave host. But when I start application which multicasts UDP packets with TTL 0, I see packets with TTL 0 leaving host for few seconds, and coming to normal behavior ...
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Why aren't my name servers updating?

I have had hundreds of domains over the years, and generally, the 24 to 48 hour rule applies. Sometimes even much quicker. I've learned that the registrar you use affects it a lot. GoDaddy usually ...
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Understanding TTL field of PTR record returned by dig client

I have some doubts about working of DNS in general - even given the fact I have theoretical base. let's consider a following output: [user@host ~]$ dig google.com [...] ;; ANSWER SECTION: google....
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3 votes
1 answer
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Moving DNS hosting for Active site to Route 53 - with G Suite MX TTL of 1 week

I am following the steps outlined in this AWS guide to transfer my domain hosting from GoDaddy to AWS. Step 4 requires me to lower TTL for my existing NS Record to avoid downtime if I encounter issues....
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Squid negative_ttl not working

Setup $ squid -v Squid Cache: Version 3.5.20 Service Name: squid configure options: '--build=x86_64-koji-linux-gnu' '--host=x86_64-koji-linux-gnu' '--program-prefix=' '--prefix=/usr' '--exec-prefix=/...
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Internal DNS TTLs

Four-site company using Windows Domain and DNS servers. Minimum of one DC/DNS server per site. One site is HQ and hosts most companywide servers and services. DNS records for Windows servers are ...
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TTL Changes During Continuous Ping

We use Viasat and have the modem plugged directly into a linux based load balancer. I SSH'ed into the loadbalancer using putty and pinged google When I pinged google this is the result: - PING 8.8....
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It's possible overwrite DNS TTL with nginx headers?

My DNS provider doesn't allow me to set a custom TTL. All my domains have a 300 (5 minutes) TTL, that is terrible low. Can I send to browser a header from nginx with a custom TTL time to overwrite ...
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set long ttl on host records before nameserver change?

I'm trying to move DNS from GD to route 53 and it seems impossible to avoid downtime, even with identical zone files in both location. From my experiments, as soon as I change to 'custom' nameservers ...
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How do I change the TTL of my DNS?

I'm using Linux DNS and I'm not sure which row I should change if I want to change the TTL of my dns.. This is the TTL part: $ORIGIN biz. $TTL 3600 sop1 IN SOA ns1.mydomain.net. ...
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configuring TTL from 1800 sec to 86400 sec on Ubuntu, nginx server

I deployed an app to Digital Ocean Ubuntu server. The app is running on NGINX. My Domain registar sent me the messages that "TTL can't be less than 86400 sec on nameservers" It is currently 1800 sec ...
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DNS zone settings before a change

I'm completely changing our WAN interface addressing (new ISP). Which DNS zone adjustments should I make to the various parameters (TTL, expire, etc.) to help propagate the changes out to the Internet ...
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Migrating DNS provider when having high NS-record TTL

I have recently migrated one of my .com-domain zones from DNS provider A to DNS provider B, however the TTL on the NS-records for the zone on provider A is very high = 432000 (5 days), and thus I feel ...
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How long does it take to update TTL (Time To Live) of a domain

Say my domain example.com has TTL set to 86400. If i change this through the registrars' panel to 60 when will this change take place? Will it need 86400 seconds ? or will it be instant? I cant find ...
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Creating TTL index on number data type

I am trying to create TTL index to delete documents older than 30 min on "generated" field for below sample document sample document: {"_id" : ObjectId("5850308c077b3d1ccc11cef0"), "generated" : ...
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2 votes
1 answer
431 views

Allowing stale DNS results

Is there any method of allowing stale DNS results to be returned? By stale, I mean, where the TTL has expired, but no new record can be obtained, likely due to the nameserver being unavailable. To ...
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What happens when multiple MX records in a DNS name have different TTLs?

I am wondering what happens when a domain name in DNS has multiple MX records with different Times to Live (TTLs)? For example, what if these are the MX records for example.com? TTL = 3 days, &...
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2 answers
3k views

possible to see remaining DNS negative cache for domain?

For normal DNS lookups, one can use Dig to get an answer including the remaining TTL for a DNS record. If that answer is from a cache, the TTL will "count down" until the next authoritative query, and ...
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I changed my TTL from 24 hours to 5 minutes. Do I need to wait 24 hours before changing the records?

I am migrating our app from a cloud server at Rackspace t a dedicated server. I want to bring the application down for ~5 minutes to copy the data from the cloud server to the dedicated server, so I ...
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7 votes
1 answer
367 views

Is there a standard time duration before DNS caches are cleared?

Is there a standard time duration before DNS caches are cleared, so that if a distracted operator or stuck key turns a TTL of 86400 into 864000000 you don't end up with an authoritative resource ...
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1 vote
1 answer
2k views

Why is TTL increasing? (and generally behaving erratically)

Summary: TTL is not decremented when pinging hosts on a "network path" My laptop (10.10.13.10) is connected via OpenVPN to a server (10.10.13.1) which hosts several network interfaces. One of them is ...
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1 answer
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Possible issues of switching DNS back and forth quickly

I don't have a ton of knowledge about DNS so I want to be as cautious as possible before I pull the trigger on a re-point. Scenario I am doing a simple migration of a website from one server to ...
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2 votes
1 answer
13k views

How to find the initial values of TTL for your current operating system?

In this answer to a question related to interpreting the values of TTL from a ping operation it is said that the TTL values vary depending on the operating system. I understood more or less the ...
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Fast switching CNAME

Is it possible to make CNAME's switch it's data every minute (or possibly even shorter) ? I'm currently trying to make something that changes my CNAME every minute but i have no idea if this is even ...
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NSCD TTL and DNS TTL, which one is stronger?

I've configured many servers in my company to work with NSCD for local caching of hosts and in order to lower traffic to the local DNS servers as well as return a quicker DNS response when possible. ...
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1 answer
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OS Fingerprinting, TTL=56? [closed]

I am just learning about OS fingerprinting, when i ping a certain ip address, it gives me a ttl value of 56. What is an operating system with a value of 56? I only know about the popular operating ...
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1 answer
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Correctly calculate DNS TTL from host -a output

I'm trying to figure out how TTLs are handled in DNS (in the end I'm trying to figure out the fastest way to switch over a domain), but somehow I'm stuck in interpreting TTL values. For example I ...
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8 votes
2 answers
638 views

Cisco DNS doctoring or Hairpinning?

I've the following configuration: CISCO 881, IOS 15.2(4)M6. On WAN interface is configured the 86.34.156.48/29 subnet from our ISP. Behind the router is staying 2 webserver. NAT: 86.34.156.51 <> ...
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Bind caching nameserver MX lookup error for Low TTL Records

We are running Bind (9.8) as Caching Nameserver on a CentOS 6.x based mail server. We get frequent domain not found error for certain domains resulting in mail delivery failure. It was discovered ...
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TTL and Google DNS

I've found a similar post about this, however my user can't comment. I wonder why doing dig @8.8.8.8 domain.com prints out different "countdowns" when running it several times in few seconds, as if ...
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3 votes
1 answer
747 views

Why does TTL sometimes re-increment between DNS queries?

I dig xkcd.com, and I get something like this back: ; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>> xkcd.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: ...
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2 answers
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TTL in ping vs dig

When I ran ping google.com, I get a ttl value of 55: 64 bytes from 173.194.127.103: icmp_seq=68 ttl=55 time=16.4 ms When I ran dig google.com @ns1.google.com., it get a TTL value of 300. google.com....
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5 votes
2 answers
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Best CNAME TTL strategy for fallover switching

I've recently been thinking about the TTL of our DNS. We have A records for our servers and then CNAME records for the customer facing names. The www.example.com CNAME points to server-01.example.com ...
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1 vote
2 answers
424 views

Bouncing email due to bad initial MX TTL?

Last Friday night we changed mail servers. We moved off Office 365 to another hosted Exchange Solution (Intermedia.net). We use Godaddy for DNS, and after the server migration stuff was ready and ...
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4 votes
2 answers
552 views

Big Trouble with (I think) Outlook X500 addressing

I moved a small client from one hosted Exchange server (Microsoft Office 365) to another (Intermedia.net). Some emails from External senders to the users on the new server host are undeliverable, ...
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0 votes
1 answer
1k views

Setting DNS TTL for an external address

To start with, I don't know jack about DNS servers. I have been stuck with resolving a problem with a DNS-Server because I discovered a problem with one of our systems and determined that it was ...
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14 votes
2 answers
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What happens when your TTL gets screwed up in your DNS record?

What happens when someone gets access to your DNS control and sets a TTL of 100 years on your domain, while pointing it's IP to some obscure website? (and you discover it too late of course)
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CDN and TTL on local EC2 files

I Have a file in CDN and I need a local copy of it in all of my EC2 instances. I like to set a TTL on the local copy of 5 minute, and have one of the following: Have it Fetch automatically as soon as ...
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5 votes
1 answer
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AWS Route 53 alias-record change takes too long

I have setup a stack in AWS Cloudformation, which is up and running. The stack contains an ELB (load balancer) and a few EC2-instances. When we do a new deployment of our application, we build a new ...
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4 votes
1 answer
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Lowering TTL on nameserver, not registrar, then changing nameservers?

A client website has their domain name registered at GoDaddy. This domain points to Wix.com's nameservers. I've lowered the TTL in wix to 1 hour. However, when we go live we'll be switching the ...
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4 votes
1 answer
2k views

Outlook.com DNS so slow, postfix times out

I'm trying to send e-mails to for example: postmaster@grassvalley.com and postmaster@jorssen.net.bmw.be. In both cases these are Outlook mailboxes. Postfix replies with: (when ipv6 enabled): ...
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0 votes
2 answers
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Change DNS TTL for every records in a zone

I have a forward lookup zone with a lot of A records. If I change the TTL for the zone, it does not apply to records (they keep the previous TTL setting). I have to manually change the TTL for every ...
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3 votes
2 answers
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Is low TTL an appreciable burden on DNS?

I currently work for an medium-sized institution whose DNS management is questionable at best. Often, there are DNS-related failures causing downtime for the entire building and our public-facing ...
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3 votes
3 answers
1k views

DNS Nameserver updates affected by TTL? or is it just A records, MX etc?

The TTL has been set to 1H, so that IP changes for example.com can be made more quickly. The registrar has been configured with ns1.example.com and ns2.example.com, verified using WHOIS lookup. ns1 ...
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