Questions tagged [ttl]
Time To Live is a mechanism to prevent messages from traversing the network indefinitely
102
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How can I see Time-To-Live (TTL) for a DNS record?
I would like to see the Time-To-Live (TTL) value for a CNAME record.
I have access to dig (on Apple Mac OS X), which gives me an answer like this:
% dig host.example.gov
<*SNIP*>
;; ANSWER ...
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60
votes
8
answers
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What does "TTL expired in transit" mean on a ping attempt?
We get the message “TTL expired in transit” when we try to ping to a server in a different network segment. When we run tracert, 4 ip addresses repeat themselves indefinitely:
14 60 ms 59 ms ...
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votes
3
answers
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Recommended DNS SOA record TTL default?
We currently have our DNS SOA record set to the following for stackoverflow.com:
primary name server = ns1.p19.dynect.net
serial = 2009090909
refresh = 3600 (1 hour)
retry = 600 (...
- 2,506
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votes
5
answers
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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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votes
2
answers
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35
votes
5
answers
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What percentage of nameservers honor TTL these days?
Some years ago I had to do several DNS changes over the course of several weeks as I moved bits of equipment from one data center to the other. At the time that I did this, about 95% of the ...
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votes
2
answers
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What does the TTL on a CNAME record mean?
Due to how many servers are involved in my network, I have a hard time keeping them all organized. Some of them don't have static IP's, so I thought it might be nice if I made a config.mydomain.com ...
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votes
7
answers
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Recommended DNS TTL
I know it could be very different based on the situation, but for hosting a website with no plans to move the hosting server what is a good TTL to set on the DNS record?
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2
answers
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Varnish Cache - default TTL?
I have discovered that I can set the TTL in Varnish as follows in my VCL file:
sub vcl_fetch {
# 1 minute
set obj.ttl = 1m;
}
But what is the default setting (assuming the backend server is ...
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20
votes
1
answer
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Can Windows 2008 R2 DNS set TTL per record?
The DNS Manager administrative tool doesn't seem to have an option for configuring TTL for an individual record. I can set the TTL per-zone by right-clicking -> Properties -> SOA. Where is the ...
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CNAME and A record have different TTLs. Which one will be cached?
If a CNAME has a TTL of 1 hour that points to an A record with a TTL of 1 minute, will someone who looks up this CNAME have the entire result cached for 1 hour, or will it will keep having to lookup ...
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2
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What are the benefits of a high TTL for DNS?
I'm moving a domain's nameservers from the registrar to dnsmadeasy.com so that we can have automatic failover (among other benefits). When I've done this in the past I simply set the TTL value as low ...
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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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votes
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Weighted round robins via TTL - possible?
I currently use DNS round robin for load balancing, which works great.
The records look like this (I have a TTL of 120 seconds)
;; ANSWER SECTION:
orion.2x.to. 116 IN A 80.237.201.41
orion....
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2
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How do I set a varnish response TTL dynamically?
my php script is sending a header X_Cache_ttl: 1h and in my varnish config file I have
sub vcl_fetch
{
if(beresp.http.X-Cache-ttl){
set beresp.ttl = beresp.http.X-Cache-ttl;
}
}
...
- 2,101
9
votes
1
answer
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How does Varnish deal with running out of storage?
I am using Varnish 3.0.3 (the latest as of this writing) with more or less the default install, using the following for storage:
# # Cache file location
VARNISH_STORAGE_FILE=/var/lib/varnish/...
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9
votes
2
answers
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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 <> ...
7
votes
1
answer
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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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votes
1
answer
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5
votes
2
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How network devices affect TTL
When I do a ping, I can see the TTL value for each packet. For every router that I insert in between my computer and the router that connects to the internet, the TTL value goes down by one. However, ...
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2
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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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2
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My TTL changing over every packetand I don't know why
Recently I discovered that some pings sent to me were giving a TTL error. When someone pings my computer, it shows a different TTL value for every packet.
For example, ping.eu shows that:
--- PING ...
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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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votes
1
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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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votes
2
answers
642
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, ...
4
votes
1
answer
2k
views
Outlook.com DNS so slow, postfix times out
I'm trying to send e-mails to for example: [email protected] and [email protected]. In both cases these are Outlook mailboxes.
Postfix replies with:
(when ipv6 enabled):
...
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4
votes
1
answer
931
views
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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votes
2
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Windows Server 2008 R2 DNS - Syncronizing changes to TTL
I apologize if this has been asked. My searches have not been successful.
If I have 2 DNS servers in my Domain and add an A record to 1 server, that record is successfully propagated to the second ...
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votes
2
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1k
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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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1
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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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What DNS Settings to use to migrate Domain from One Server to Another
I am going to migrate a site from one server to another. The site has a good bit of realtime transaction activity reading/writing to a backend database.
I believe I should ratchet down the TTL in the ...
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3
votes
1
answer
367
views
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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2
answers
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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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votes
3
answers
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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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2
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How long does azure cdn live before updating
I am using the windows Azure CDN,
And not like Amazon's one cannot configure any TTL regarding the files,
I was wondering if there is any official document microsoft had regarding to the Time-to-...
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5
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2k
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Generating ICMP packets when TTL=2?
By inspecting the payload of ICMP time-exceeded packets, I noticed that sometimes it is the last but one router (when ttl=2 in the returned packet) or even a previous one(up to 5 hops before, ttl=5) ...
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votes
1
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3k
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Will setting my DNS TTL to 86400 prevent minor DNS outages from making my site unavailable?
This morning, Network Solutions (where we host our DNS) had some intermittent DNS Server outages. All of our sites were inaccessible during this time. When network solutions DNS Servers came back up, ...
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votes
3
answers
3k
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Using a low TTL to help prevent extended periods of downtime
Is it feasible to set my domain's TTL to a very low value (a couple of minutes) so that, if my main host goes down for an extended period of time, I can update the DNS records in my main host to point ...
2
votes
2
answers
12k
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Differences of the TTL value in Tracert and Ping
When I ping localhost on my Windows XP system, the TTL value returned is 128 and it shows me that the default TTL value in the ping for my system is 128.
Then when I ping google.com the returned TTL ...
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votes
1
answer
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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 ...
user236846
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2
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bind9; how to automatically refresh entry after entry expires
I am looking for a way to automatically refresh entries in my cache if it expires.
For example, example.com has a TTL of 60, i would like to automatically refresh it if it expires so that when users ...
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2
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Understanding how Tracert works
From what I gathered so far, Tracert works by sending 3 ICMP echo messages. Starting with a TTL value of 1. For each router the packet encounters, the TTL value will be decremented. For the 1st router,...
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votes
2
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Recommend a content delivery network (CDN) for a specific purpose [closed]
could you please recommend a CDN for the following use:
1) Ability to update files on the edge servers automatically through API, so it should take no more than 5-10 minutes to make a new version of ...
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2
votes
1
answer
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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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2
votes
1
answer
7k
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Multiple $TTL statements in bind DNS zone file
I'm using a socks proxy to connect to servers using another application. The proxy, which runs on Solaris 10. The server hosting the proxy is configured to use our own internal DNS server (bind) to ...
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2
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4k
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Optimizing TTL values for DYNDNS service
I've finally gotten my own DYNDNS working but I am looking for some advice on optimizing it.
Edit: Basiclly I got a Domain at a registrar that I point to my own nameservers where I keep my own ...
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1
answer
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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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2
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How to actually set max-age headers on Windows Server?
I've set the max age to 1 minute, but when I look at the response headers, I see max-age=86400 (one day). Is something else overriding this setting? I've also set the kernel cache to 1 minute for ...
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1
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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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2
votes
1
answer
522
views
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 ...
- 151