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

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27
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3answers
3k views

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 ...
7
votes
1answer
298 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 ...
0
votes
1answer
38 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 ...
1
vote
1answer
33 views

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 ...
1
vote
1answer
33 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 ...
0
votes
0answers
24 views

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 ...
1
vote
1answer
156 views

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. ...
-2
votes
1answer
512 views

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 ...
1
vote
1answer
148 views

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 ...
7
votes
1answer
179 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 <> ...
0
votes
0answers
76 views

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 ...
0
votes
1answer
463 views

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 ...
3
votes
1answer
179 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: ...
-3
votes
2answers
318 views

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. ...
3
votes
2answers
698 views

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 ...
1
vote
2answers
96 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 ...
4
votes
2answers
184 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, ...
0
votes
1answer
258 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 ...
12
votes
2answers
518 views

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)
0
votes
1answer
59 views

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 ...
2
votes
1answer
2k views

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 ...
2
votes
1answer
564 views

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 ...
3
votes
1answer
823 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): ...
0
votes
2answers
3k views

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 ...
3
votes
2answers
343 views

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 ...
2
votes
3answers
581 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 ...
-1
votes
1answer
89 views

TTL on DNS for domains as a security measure [closed]

Ever since I read this article the other day, I've felt a bit uncomfortable about my domains being stolen. And I've tried taking each measure possible. But one I don't understand completely is TTL. ...
1
vote
1answer
3k views

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 ...
0
votes
1answer
1k views

ICMP echo-reply packets with a much lower TTL (-190) than ICMP time-exceeded packets

When I ping the last three hops of a traceroute path to facebook.com from my location, the ICMP echo-reply packets I get back all have a TTL of respectively 58, 57 and 56. The hops in question are the ...
1
vote
1answer
179 views

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 ...
0
votes
1answer
97 views

Fun this TTLs and many records in PDNS

I got very strange issue for me. I have powerdns server with potentially thousands of cname records. This records inserted to my DNS via mysql queries from network http service. This is a way how I ...
2
votes
1answer
440 views

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, ...
3
votes
2answers
1k views

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 ...
1
vote
1answer
787 views

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 ...
6
votes
1answer
2k views

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; } } ...
9
votes
1answer
3k views

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 ...
2
votes
5answers
621 views

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) ...
-2
votes
4answers
346 views

Reducing TTL in DNS

What stops us from reducing the TTL of all DNS entries to 1 minute or something less? If that is done we won't have to wait mych for DNS changes to propagate so what all things force us to not do ...
1
vote
2answers
138 views

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 ...
0
votes
1answer
157 views

Can't change serials in my SOA without breaking my nameservers

So I was testing my DNS using http://www.intodns.com/mydomain.com And it gave me a warning about the serials of my two nameservers not matching. So I changed the serials to match and restarted bind ...
1
vote
2answers
1k views

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 ...
1
vote
1answer
574 views

TTL and traceroute showing different values for same domain

Why am I getting two different outputs for tracert and ping? Ping Result showing total hops of 20 and tracert showing 8. Default ttl value on my Linux machine 64, icmp echo reply ttl value 44. ...
0
votes
1answer
873 views

Variable TTL inside a LAN

I recently discovered that ping my local router, returns different TTL values​​. The ping 3 switch must pass through before reaching the router, there may be the problem? 192.168.1.99 is the IP of my ...
1
vote
0answers
433 views

Squid 3.1: external_acl_type ttl won't work

I have custom script for handling Squid3's external_acl_type and it works fine. In this script (btw, its PHP) I turned on logging every request into the file. As far as I know from docs TTL value ...
4
votes
2answers
624 views

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 ...
5
votes
2answers
2k views

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 ...
3
votes
1answer
2k views

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 ...
18
votes
2answers
17k views

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 ...
9
votes
2answers
10k views

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 ...
0
votes
2answers
204 views

Can I find out whether my DNS provider honor my TTL settting?

Is there any way to determine if my DNS provider actually use the TTL setting I provide?