Server Fault Stack Exchange
Server Fault Stack Exchange

Questions tagged [ttl]

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

Every IP packet has a Time To Live, it is a counter that gets deducted when it passes a router. It prevents a packet from traversing the network endlessly. If the packets TTL reaches 0 it gets discarded. TTL can be a timestamp or a counter.

101 questions
127
votes
4 answers

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 SECTION: host.example.gov. 43200 IN CNAME …
Stefan Lasiewski
  • 23,667
  • 41
  • 132
  • 186
59
votes
8 answers

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 60 ms xxx.xxx.xxx.2 15 83 ms 81 ms 82…
Leonardo
  • 695
  • 1
  • 5
  • 8
48
votes
3 answers

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 (10 mins) expire = 604800 (7 days) default…
Geoff Dalgas
  • 2,476
  • 5
  • 31
  • 32
37
votes
5 answers

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 don't want requests going to the old server after…
wobbily_col
  • 653
  • 2
  • 7
  • 14
35
votes
5 answers

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 nameservers in the world seemed to respect the TTL value,…
user10501
  • 682
  • 1
  • 5
  • 7
35
votes
2 answers

Any disadvantage to short DNS TTL?

Any disadvantage to short DNS TTL?
webnat0
  • 623
  • 2
  • 8
  • 13
32
votes
2 answers

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 domain. On this domain, I could store A records and…
Ryan Pendleton
  • 446
  • 1
  • 4
  • 9
28
votes
7 answers

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?
Brian Fisher
  • 641
  • 3
  • 10
  • 15
24
votes
2 answers

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 setting no cache-control header) ?
Ade
  • 699
  • 3
  • 10
  • 21
20
votes
1 answer

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 equivalent for each record?
sh-beta
  • 6,838
  • 7
  • 47
  • 66
20
votes
3 answers

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 the A record every 1 minute?
Sean
  • 379
  • 2
  • 3
  • 8
19
votes
2 answers

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 as it can go (1 minute) for the A record so that…
Charlie Schliesser
  • 440
  • 1
  • 4
  • 12
15
votes
2 answers

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)
Dirk Boer
  • 485
  • 1
  • 3
  • 10
10
votes
5 answers

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.2x.to. 116 IN A …
The Shurrican
  • 2,240
  • 7
  • 39
  • 60
9
votes
2 answers

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 <> 10.10.10.100 (private IP, server1). If I configure…
Szilveszter Zsigmond
  • 143
  • 1
  • 1
  • 9
1
2 3 4 5 6 7